/* i650_cpu.c: IBM 650 CPU simulator
Copyright (c) 2018, Roberto Sancho
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
ROBERTO SANCHO BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
cpu IBM 650 central processor
From Wikipedia: The IBM 650 Magnetic Drum Data-Processing Machine is one of
IBM's early computers, and the world�s first mass-produced computer. It was
announced in 1953 and in 1956 enhanced as the IBM 650 RAMAC with the
addition of up to four disk storage units. Almost 2,000 systems were
produced, the last in 1962.
The 650 was a two-address, bi-quinary coded decimal computer (both data and
addresses were decimal), with memory on a rotating magnetic drum. Character
support was provided by the input/output units converting punched card
alphabetical and special character encodings to/from a two-digit decimal
code.
Rotating drum memory provided 1,000, 2,000, or 4,000 words of memory (a
signed 10-digit number or five characters per word) at addresses 0000 to
0999, 1999, or 3999 respectively.
Instructions read from the drum went to a program register (in current
terminology, an instruction register). Data read from the drum went through
a 10-digit distributor. The 650 had a 20-digit accumulator, divided into
10-digit lower and upper accumulators with a common sign. Arithmetic was
performed by a one-digit adder. The console (10 digit switches, one sign
switch, and 10 bi-quinary display lights), distributor, lower and upper
accumulators were all addressable; 8000, 8001, 8002, 8003 respectively.
The 650 instructions consisted of a two-digit operation code, a four-digit
data address and the four-digit address of the next instruction. The sign
was ignored on the basic machine, but was used on machines with optional
features. The base machine had 44 operation codes. Additional operation
codes were provided for options, such as floating point, core storage,
index registers and additional I/O devices. With all options installed,
there were 97 operation codes.
The programmer visible system state for the IBM 650 is:
CSW <10:1> Console Switches
ACC[0] <10:1> Lower Accumulator register
ACC[1] <10:1> Upper Accumulator register
DIST <10:1> Distributor
OV<0:0> Overflow flag
The 650 had one basic instuction format.
Intructions are stores as 10 digits (0-9) words in drum memory
10 9 | 8 7 6 5 | 4 3 2 1 | 0
-----+---------+---------+-----
op | Data | Instr | Sign
code | Addr | Addr
First two digits are opcodes
digits 8-5 is data address referenced by opcode
digits 4-1 is instruction address: address of next instruction
Instruction support as described in BitSavers 22-6060-2_650_OperMan.pdf
IBM 653 Storage Unit can be enabled as an option. This simulates the following
- Immediate Access Storage (IAS)
- Index registers
- Floating Point support
- Synchronizers 2 & 3
*/
#include "i650_defs.h"
#define UNIT_V_MSIZE (UNIT_V_UF + 0)
#define UNIT_MSIZE (7 << UNIT_V_MSIZE)
#define UNIT_V_CPUMODEL (UNIT_V_UF + 4)
#define UNIT_MODEL (0x01 << UNIT_V_CPUMODEL)
#define CPU_MODEL ((cpu_unit.flags >> UNIT_V_CPUMODEL) & 0x01)
#define MODEL(x) (x << UNIT_V_CPUMODEL)
#define MEMAMOUNT(x) (x << UNIT_V_MSIZE)
#define OPTION_STOR (1 << (UNIT_V_CPUMODEL + 1))
#define OPTION_CNTRL (1 << (UNIT_V_CPUMODEL + 2))
#define OPTION_SOAPMNE (1 << (UNIT_V_CPUMODEL + 3))
#define OPTION_FAST (1 << (UNIT_V_CPUMODEL + 4))
t_stat cpu_ex(t_value * vptr, t_addr addr, UNIT * uptr, int32 sw);
t_stat cpu_dep(t_value val, t_addr addr, UNIT * uptr, int32 sw);
t_stat cpu_reset(DEVICE * dptr);
t_stat cpu_set_size(UNIT * uptr, int32 val, CONST char *cptr, void *desc);
t_stat cpu_help (FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
t_stat cpu_svc (UNIT *uptr);
const char *cpu_description (DEVICE *dptr);
// DRUM Memory
t_int64 DRUM[MAXDRUMSIZE] = {0};
int DRUM_NegativeZeroFlag[MAXDRUMSIZE] = {0};
char DRUM_Symbolic_Buffer[MAXDRUMSIZE * 80] = {0}; // does not exists on real hw. Used to keep symbolic info
// IO Synchronizer for card read-punch buffer
t_int64 IOSync[10] = {0};
int IOSync_NegativeZeroFlag[10] = {0};
// IAS Memory
t_int64 IAS[60] = {0};
int IAS_NegativeZeroFlag[60] = {0};
int IAS_TimingRing = 0;
// interlock counters
int InterLockCount[IL_array] = {0};
// address where rotating drum is currently positioned (0-49)
int DrumAddr;
// cpu registers
uint16 IC; // Added register not part of cpu. Has addr of current intr in execution, just for displaying purposes. IBM 650 has no program counter
uint16 PROP; // Added register not part of cpu. Has operation code of current intr in execution, just for scp scripting purposes. Contains the two higher digits of PR register
t_int64 ACC[2]; /* lower, upper accumulator. 10 digits (=one word) each*/
t_int64 DIST; /* ditributor. 10 digits */
t_int64 CSW = 0; /* Console Switches, 10 digits */
t_int64 PR; /* Program Register: hold current instr in execution, 10 digits*/
uint16 AR; /* Address Register: address references to drum */
uint8 OV; /* Overflow flag */
uint8 CSWProgStop = 1; /* Console programmed stop switch */
uint8 CSWOverflowStop = 0; /* Console stop on overflow switch */
uint8 HalfCycle = 0; // set to 0 for normal run, =1 to execute I-Half-cycle, =2 to execute D-half-cycle
int ProgStopFlag = 0; // set to 1 if programmed stop was the previous inst executed
int AccNegativeZeroFlag = 0; // set to 1 if acc has a negative zero
int DistNegativeZeroFlag = 0; // set to 1 if distributor has a negative zero
int16 IR[3]; // Index registers. Are 4 digits as AR register, but signed
/* CPU data structures
cpu_dev CPU device descriptor
cpu_unit CPU unit descriptor
cpu_reg CPU register list
cpu_mod CPU modifiers list
*/
UNIT cpu_unit =
{ UDATA(&cpu_svc, MEMAMOUNT(0)|MODEL(0x0), 1000), 10 };
REG cpu_reg[] = {
{DRDATAD(IC, IC, 16, "Current Instruction"), REG_FIT|REG_RO},
{DRDATAD(PROP, PROP, 16, "Program Register Operation Code"), REG_FIT|REG_RO},
{HRDATAD(DIST, DIST, 64, "Distributor"), REG_VMIO|REG_FIT},
{HRDATAD(ACCLO, ACC[0], 64, "Lower Accumulator"), REG_VMIO|REG_FIT},
{HRDATAD(ACCUP, ACC[1], 64, "Upper Accumulator"), REG_VMIO|REG_FIT},
{HRDATAD(PR, PR, 64, "Program Register"), REG_VMIO|REG_FIT},
{DRDATAD(AR, AR, 16, "Address Register"), REG_FIT},
{ORDATAD(OV, OV, 1, "Overflow"), REG_FIT},
{HRDATAD(CSW, CSW, 64, "Console Switches"), REG_VMIO|REG_FIT},
{ORDATAD(CSWPS, CSWProgStop, 1, "Console Switch Program Stop"), REG_FIT},
{ORDATAD(CSWOS, CSWOverflowStop, 1, "Console Switch Overflow Stop"), REG_FIT},
{ORDATAD(HALF, HalfCycle, 2, "Half Cycle"), REG_FIT},
{NULL}
};
MTAB cpu_mod[] = {
{UNIT_MSIZE, MEMAMOUNT(0), "1K", "1K", &cpu_set_size},
{UNIT_MSIZE, MEMAMOUNT(1), "2K", "2K", &cpu_set_size},
{UNIT_MSIZE, MEMAMOUNT(2), "4K", "4K", &cpu_set_size},
{OPTION_STOR, 0, NULL, "NOSTORAGEUNIT", NULL},
{OPTION_STOR, OPTION_STOR, "Storage Unit", "STORAGEUNIT", NULL},
{OPTION_CNTRL, 0, NULL, "NOCNTRLUNIT", NULL},
{OPTION_CNTRL, OPTION_CNTRL, "Control Unit", "CNTRLUNIT", NULL},
{OPTION_SOAPMNE, 0, NULL, "DEFAULTMNE", NULL},
{OPTION_SOAPMNE, OPTION_SOAPMNE, "Using SOAP Mnemonics", "SOAPMNE", NULL},
{OPTION_FAST, 0, NULL, "REALTIME", NULL},
{OPTION_FAST, OPTION_FAST, "Fast Execution", "FAST", NULL},
{0}
};
DEVICE cpu_dev = {
"CPU", &cpu_unit, cpu_reg, cpu_mod,
1, 10, 16, 1, 10, 64,
&cpu_ex, &cpu_dep, &cpu_reset, NULL, NULL, NULL,
NULL, DEV_DEBUG, 0, dev_debug,
NULL, NULL, &cpu_help, NULL, NULL, &cpu_description
};
t_stat cpu_svc (UNIT *uptr)
{
// poll kbd to sense ^E to halt cpu execution.
sim_activate_after (uptr, 300*1000); // poll each 300 msec
sim_poll_kbd();
return SCPE_OK;
}
// return 0 if addr invalid, 1 if addr valid depending on allowed addrs given by ValidDA
// set the ias TimingRing to AR is IAS is accessed
int IsDrumAddrOk(int AR, int ValidDA)
{
// check if AR should be 9000
if ((STOR) && (ValidDA & vda_9000))
return (AR == 9000) ? 1:0;
// Drum address
if ((AR >= 0) && (AR < DRUMSIZE))
return (ValidDA & vda_D) ? 1:0;
// cpu registers: acc (lo&hi), distibutor, console swithc reg: ok to check for Addr validity, ok to read, cannot write to it
if ((AR >= 8000) && (AR <= 8003))
return (ValidDA & vda_A) ? 1:0;
// index registers (ir) present if Storage Unit is enabled: ok to check for Addr validity, ok to read, cannot write to it
if ((STOR) && (AR >= 8005) && (AR <= 8007))
return (ValidDA & vda_I) ? 1:0;
// tape address present is tapes are enabled: ok to check for Addr validity, cannot read/write to it
if ((CNTRL) && (AR >= 8010) && (AR <= 8015))
return (ValidDA & vda_T) ? 1:0;
// inmediate access storage (ias) if Storage Unit is enabled: ok to check for Addr validity, ok to read/write
if ((STOR) && (AR >= 9000) && (AR <= 9059)) {
if (ValidDA & vda_S) {
IAS_TimingRing = AR - 9000; // set Timing ring on address accesed
return 1;
}
}
// none of the above -> invalid address or address/mode combination
return 0;
}
// return 0 if write addr invalid
int WriteAddr(int AR, t_int64 d, int NegZero)
{
if (d) NegZero = 0; // sanity check on Minus Zero
if ((STOR) && (AR >= 9000) && (AR <= 9059)) { // IAS is available at addr 9000-9059
IAS_TimingRing = AR - 9000; // not necessary as before any call to WriteAddr IsAddrOk is invoked. But ... just in case
IAS[IAS_TimingRing] = d;
IAS_NegativeZeroFlag[IAS_TimingRing] = NegZero;
return 1;
} else if ((AR >= 0) && (AR < DRUMSIZE) && (AR < MAXDRUMSIZE)) {
if (d) NegZero = 0; // sanity check on Minus Zero
DRUM[AR] = d;
DRUM_NegativeZeroFlag[AR] = NegZero;
return 1;
}
// none of the above -> invalid address or address/mode combination
return 0;
}
// return 0 if read addr invalid
int ReadAddr(int AR, t_int64 * d, int * NegZero)
{
int neg;
// read from drum?
if ((AR >= 0) && (AR < DRUMSIZE)) {
*d = DRUM[AR];
neg = DRUM_NegativeZeroFlag[AR];
if (*d) DRUM_NegativeZeroFlag[AR] = 0;
} else
// read from cpu registers?
if (AR == 8000) {*d = CSW; neg=0; } else
if (AR == 8001) {*d = DIST; neg=DistNegativeZeroFlag; } else
if (AR == 8002) {*d = ACC[0]; neg=AccNegativeZeroFlag; } else
if (AR == 8003) {*d = ACC[1]; neg=AccNegativeZeroFlag; } else
// read index registers (ir) ?
if ((STOR) && (AR == 8005)) {*d = IR[0]; neg=0; } else
if ((STOR) && (AR == 8006)) {*d = IR[1]; neg=0; } else
if ((STOR) && (AR == 8007)) {*d = IR[2]; neg=0; } else
// tape address ?
if ((CNTRL) && (AR >= 8010) && (AR <= 8015)) {
// cannot read/write to tape addresses
return 0;
} else
// read inmediate access storage (ias)?
if ((STOR) && (AR >= 9000) && (AR <= 9059)) {
IAS_TimingRing = AR - 9000;
*d = IAS[IAS_TimingRing];
neg = IAS_NegativeZeroFlag[IAS_TimingRing];
if (*d) IAS_NegativeZeroFlag[IAS_TimingRing] = 0;
} else {
// none of the above -> invalid address for read
return 0;
}
if (*d) neg = 0; // sanity check on Minus Zero
if (NegZero != NULL) *NegZero = neg;
return 1;
}
// shift acc 1 digit. If direction > 0 to the left, if direction < 0 to the right.
// Return digit going out of acc (with sign)
int ShiftAcc(int direction)
{
t_int64 a0, a1;
int neg = 0;
int n, m;
n = 0;
a1 = ACC[1]; if (a1 < 0) {a1 = -a1; neg = 1;}
a0 = ACC[0]; if (a0 < 0) {a0 = -a0; neg = 1;}
if ((AccNegativeZeroFlag) && (ACC[0] == 0) && (ACC[1] == 0)) neg = 1;
if (direction > 0) { // shift left
n = Shift_Digits(&a1, 1); // n = Upper Acc high digit shifted out on the left
m = Shift_Digits(&a0, 1); // m = intermediate digit that goes from one acc to the other
a1 = a1 + (t_int64) m;
} else if (direction < 0) { // shift right
m = Shift_Digits(&a1, -1); // m = intermediate digit that goes from one acc to the other
n = Shift_Digits(&a0, -1); // n = Lower Acc units digit shifted out on the right
a0 = a0 + (t_int64) m * (1000000000L);
}
if (neg) {a1=-a1; a0=-a0; n=-n;}
ACC[0] = a0;
ACC[1] = a1;
if ((neg == 1) && (a0 == 0) && (a1 == 0)) AccNegativeZeroFlag = 1;
return n;
}
// float value format = mmmmmmmcc = 0.m x 10^(c-50)
// mmmmmmm = mantissa
// cc = modified characteristic (== exponent)
// get modified characteristic of float d
int GetExp(t_int64 d)
{
return (AbsWord(d) % 100);
}
// set modified characteristic of float d
t_int64 SetExp(t_int64 d, int exp)
{
int neg = 0;
if (d < 0) {neg=1; d=-d;}
d = ((d / 100) * 100) + (exp % 100);
if (neg) d=-d;
return d;
}
// set result into ACC[1] and ACC[0] for float mult and division
// get a 10 digits mantissa en ACC[1]
// round to the 8th digit
// add the modified characteristic (exp)
// add sign, check for zero
void MantissaRoundAndNormalizeToFloat(int * CpuStepsUsed, int neg, int exp)
{
// if high order digit of mantissa is zero, shift left once
if (Get_HiDigit(ACC[1]) == 0) {
ShiftAcc(1);
*CpuStepsUsed = *CpuStepsUsed + 2;
if (exp == 0) {
OV = 1;
} else {
exp--;
}
}
// round mantissa in ACC[1] to the 8th digit
if (GetExp(ACC[1]) >= 50) {
ACC[1] = ACC[1] + 100;
if (ACC[1] >= D10) {
ACC[1] = ACC[1] / 10;
*CpuStepsUsed = *CpuStepsUsed + 2;
if (exp == 99) {
OV = 1;
} else {
exp++;
}
}
}
ACC[1] = SetExp(ACC[1], 0);
// normalize mantissas
while (( ACC[1] != 0) && (Get_HiDigit(ACC[1]) == 0)) {
if (exp == 0) {
OV = 1;
break; // if zero, underflow
} else {
exp--;
}
ACC[1] = ACC[1] * 10;
*CpuStepsUsed = *CpuStepsUsed + 2;
}
// set result
if (exp < 0) {exp += 100; OV = 1;}
if (exp > 99) {exp -= 100; OV = 1;}
ACC[1] = neg * SetExp(ACC[1], exp);
ACC[0] = 0;
if ((ACC[1] / 100) == 0) ACC[1] = 0; // if mantissa is zero, all is zero
AccNegativeZeroFlag = 0;
}
// add float to accumulator, set Overflow
// return number of steps used
int AddFloatToAcc(int bSubstractFlag, int bAbsFlag, int bNormalizeFlag)
{
int nSteps;
int n, neg;
t_int64 d;
OV = 0; AccNegativeZeroFlag = 0;
nSteps = 0;
n = GetExp(ACC[1]) - GetExp(DIST);
if (n == 0) {
// no decimal aligning necessary. Mantissas ready to being added
} else if ( n > 8) {
DIST = ACC[1]; ACC[1] = 0;
} else if ( n < -8) {
ACC[1] = 0;
} else {
if (n < 0) { // if between -1 and -8
n = -n; // just remove sign on number of shifts to be done
} else { // if between 1 and 8
d = ACC[1];
ACC[1] = DIST; DIST = d; // exchange distrib and upper acc
nSteps += 2;
}
ACC[1] = SetExp(ACC[1], 0); // modified characteristic of upper set to zero
while (n>0) { // shift right n digits
ShiftAcc(-1);
nSteps += 2;
n--;
}
if (GetExp(ACC[1]) >= 50) { // should round?
ACC[1] = ACC[1] + ((ACC[1] >= 0) ? 100:-100);
}
}
d = DIST;
if (bAbsFlag) if (d < 0) d = -d;
if (bSubstractFlag) d = -d;
if (((ACC[1] > 0) && (d < 0)) || ((ACC[1] < 0) && (d > 0))) nSteps += 4;
ACC[1] = (ACC[1] / 100) + (d / 100); // add/substract mantissas (positions 10-3)
n = GetExp(DIST); // get modified characteristic from dist
if (ACC[1] < 0) {
ACC[1] = -ACC[1]; neg=-1;
} else {
neg=1;
}
if (ACC[1] >= D8) { // overflow?
if ((ACC[1] % 10) >= 5) { // should round?
ACC[1] = ACC[1] / 10 + 1; // yes, shift right, keep extra 1 in high pos, add rounding
nSteps += 4;
} else {
ACC[1] = ACC[1] / 10; // no, just shift
}
n++; // add 1 to dist modified characteristic
if (n > 99) {OV = 1; n=0;} // overflow. Set modified characteristic to zero
nSteps += 4;
}
if (ACC[1] == 0) {
n = 0; // if mantissa is zero, mod. char is set to zero also
bNormalizeFlag = 0; // must not normalize
nSteps += 2;
}
ACC[1] = SetExp(neg * ACC[1] * 100, n); // insert modified characteristic of dist into upper acc
ACC[0] = 0; // lower acc set to zero
if (bNormalizeFlag) {
while(Get_HiDigit(ACC[1]) == 0) { // while hi digit (digit 10) is zero -> normalize
n = GetExp(ACC[1]); // get modified characteristic
if (n == 0) {
OV = 1; break; // if zero, underflow
}
n--;
ACC[1] = SetExp(ACC[1]/100 * 1000, n); // left shift mantissa, set modified characteristic
nSteps += 3;
}
}
return nSteps;
}
int bAccNegComplement; // flag to signals acc has complemented a negative ass (== sign adjust)
// needed to compute execution cycles taken by the intruction
// add to accumulator, set Overflow
void AddToAcc(t_int64 a1, t_int64 a0, int bSetOverflow)
{
OV = 0; AccNegativeZeroFlag = 0;
bAccNegComplement = 0;
ACC[0] += a0;
ACC[1] += a1;
// adjust carry from Lower ACC to Upper Acc
if (ACC[0] >= D10) { ACC[0] -= D10; ACC[1]++; }
if (ACC[0] <= -D10) { ACC[0] += D10; ACC[1]--; }
// ajust sign
if ((ACC[0] > 0) && (ACC[1] < 0)) {
ACC[0] -= D10; ACC[1]++;
bAccNegComplement = 1;
}
if ((ACC[0] < 0) && (ACC[1] > 0)) {
ACC[0] += D10; ACC[1]--;
bAccNegComplement = 1;
}
// check overflow
if (bSetOverflow) {
if ((ACC[1] >= D10) || (ACC[1] <= -D10)) {
ACC[1] = ACC[1] % D10;
OV=1;
}
}
}
t_int64 SetDA(t_int64 d, int DA)
{
int neg = 0;
int op, nn, IA;
if (DA < 0) DA=-DA;
if (d < 0) {d=-d; neg=1;}
// extract parts of word
op = Shift_Digits(&d, 2);
nn = Shift_Digits(&d, 4); // discard current DA
IA = Shift_Digits(&d, 4);
// rebuild word with new DA
d = (t_int64) op * D8 +
(t_int64) DA * D4 +
(t_int64) IA;
if (neg) d=-d;
return d;
}
// set last 4 digits in d with IA contents
t_int64 SetIA(t_int64 d, int IA)
{
int neg = 0;
if (IA < 0) IA=-IA;
if (d < 0) {d=-d; neg=1;}
d = d - ( d % D4);
d = d + (IA % D4);
if (neg) d=-d;
return d;
}
// set last 2 digits in d with IA contents
t_int64 SetIA2(t_int64 d, int n)
{
int neg = 0;
if (n < 0) n=-n;
if (d < 0) {d=-d; neg=1;}
d = d - ( d % 100);
d = d + ( n % 100);
if (neg) d=-d;
return d;
}
// normalize to 4 digits, 10 complements
void NormalizeAddr(int * addr)
{
while (*addr >= 10000) *addr -= 10000;
while (*addr < 0) *addr += 10000;
}
// apply index register to a tagged address
// removes tag, replace value with developed address
// return 1 if address was tagged, and has been replaced by developed addr
int ApplyIndexRegister(int * addr)
{
int n = 0;
int norm = 0;
// check for tag and untag
if ((*addr >= 2000) && (*addr < 4000)) {n = 1; norm = 2000; } else
if ((*addr >= 4000) && (*addr < 6000)) {n = 2; norm = 4000; } else
if ((*addr >= 6000) && (*addr < 8000)) {n = 3; norm = 6000; } else
if ((*addr >= 9200) && (*addr < 9260)) {n = 1; norm = 200; } else
if ((*addr >= 9400) && (*addr < 9460)) {n = 2; norm = 400; } else
if ((*addr >= 9600) && (*addr < 9660)) {n = 3; norm = 600; } else
return 0; // address not tagged
*addr = *addr + IR[n-1] - norm;
NormalizeAddr(addr);
return 1;
}
// opcode decode
// input: prior to call DecodeOpcode PR cpu register must be loaded with the word to decode
// output: decoded instruction as opcode, DA, IA parts
// returns opname: points to opcode name or NULL if undef opcode
CONST char * DecodeOpcode(t_int64 d, int * opcode, int * DA, int * IA)
{
CONST char * opname;
*opcode = Shift_Digits(&d, 2); // current inste opcode
*DA = Shift_Digits(&d, 4); // addr of data used by current instr
*IA = Shift_Digits(&d, 4); // addr of next instr
opname = (cpu_unit.flags & OPTION_SOAPMNE) ? base_ops[*opcode].name2 : base_ops[*opcode].name1;
if (base_ops[*opcode].option == opStorUnit) {
// opcode available if IBM 653 Storage Unit is present
if (STOR == 0) return NULL;
} else if (base_ops[*opcode].option == opCntrlUnit) {
// opcode available if IBM 652 Control Unit is present
if (CNTRL == 0) return NULL;
}
return opname;
}
// transfer (copy words) between IAS and DRUM
// dir = "D->I" or "I->D"
// bEOB = 1 -> End of IAS band terminated transfer
// return number of words transfered
int TransferIAS(CONST char * dir, int bEOB)
{
int n, f0, t0, f1, t1, ec;
n = f0 = t0 = f1 = t1 = ec = 0;
while (1) {
if (dir[0] == 'D') {
IAS[IAS_TimingRing] = DRUM[AR];
IAS_NegativeZeroFlag[IAS_TimingRing] = DRUM_NegativeZeroFlag[AR];
if (n==0) {f0=AR; t0=IAS_TimingRing;}
f1=AR; t1=IAS_TimingRing;
} else {
DRUM[AR] = IAS[IAS_TimingRing];
DRUM_NegativeZeroFlag[AR] = IAS_NegativeZeroFlag[IAS_TimingRing];
if (n==0) {t0=AR; f0=IAS_TimingRing;}
t1=AR; f1=IAS_TimingRing;
}
n++;
if ((AR % 50) == 49) { ec = 0; break; }
if (IAS_TimingRing == 9059) { ec = 1; break; }
if ((bEOB) && ((IAS_TimingRing % 10) == 9)) { ec = 2; break; }
AR++; IAS_TimingRing++;
}
sim_debug(DEBUG_DATA, &cpu_dev, " ... Copy %04d-%04d to %04d-%04d (%d words)\n",
f0, f1, t0, t1, n);
sim_debug(DEBUG_DATA, &cpu_dev, " ended by end of %s condition\n",
(ec == 0) ? "Drum band" : (ec == 1) ? "IAS" : "IAS Block");
IAS_TimingRing = (IAS_TimingRing + 1) % 60; // incr timing ring at end of pch
return n;
}
// opcode execution
// input: opcode, DA (data address), DrumAddr (current word under the r/w heads. Needed to calculate time used on instr execution)
// prior to call ExecOpcode DIST cpu register must be loaded with the needed data for inst execution
// output: bBranchToDA: =1 if next inst must be taken from DA register instead of DA
// CpuStepsUsed: number of steps (=word time) used on program execution
t_stat ExecOpcode(int opcode, int DA,
int * bBranchToDA,
int DrumAddr,
int * CpuStepsUsed)
{
t_stat reason = 0;
t_int64 d;
int i, n, neg;
int bUsingIAS;
*bBranchToDA = 0;
*CpuStepsUsed = 0;
switch(opcode) {
case OP_NOOP : // No operation
if ((IC == 0) && ((PR % D4) == 0)) reason = STOP_HALT; // if loop on NOOP on addr zero -> machine idle -> stop cpu
break;
case OP_STOP : // Stop if console switch is set to stop, otherwise continue as a NO-OP
if (CSWProgStop) {
reason = STOP_PROG;
// stops has the consequence to prevent AR to be set with IA contents (to point to next instruction).
// so must set a flag so next setp/go scp command will take next inst to execute from
// IA field in PR reg instead of AR
ProgStopFlag = 1;
}
break;
// arithmetic
case OP_RAL: // Reset and Add into Lower
case OP_RSL: // Reset and Subtract into Lower
case OP_RAABL: // Reset and Add Absolute into Lower
case OP_RSABL: // Reset and Subtract Absolute into Lower
d = DIST;
if ((opcode == OP_RAABL) || (opcode == OP_RSABL)) d = AbsWord(d);
if ((opcode == OP_RSL) || (opcode == OP_RSABL)) d = -d;
OV = 0; AccNegativeZeroFlag = 0;
ACC[1] = 0;
ACC[0] = d;
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
// sequence chart for Add/Substract
// (1) (0..49) (1) (0/1) (2) (0/2) (1)
// Enable Search Data to Wait Dist to Complement Remove A
// Dist Data dist for even Acc Neg Sum interlock
// (1) (1) (1) (0..49)
// Restart IA to AR Enable PR Search next
// Signal Inst
*CpuStepsUsed = 1+1+2+1
+(DrumAddr % 2); // using lower acc -> wait for even
// no need to complement neg sum
break;
case OP_AL: // Add to Lower
case OP_SL: // Subtract from Lower
case OP_AABL: // Add Absolute to lower
case OP_SABL: // Subtract Absolute from lower
if ((opcode == OP_AL) && (ACC[1] == 0) && (ACC[0] == 0) && (AccNegativeZeroFlag) &&
(DIST == 0) && (DistNegativeZeroFlag)) {
// special case as stated in Operation manual 22(22-6060-2_650_OperMan.pdf), page 95
// Acc result on minus zero if acc contains minus zero and AU or AL with a drum
// location that contains minus zero
OV=0;
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: 0000000000 0000000000- (Minus Zero), OV: 0\n");
// acc keeps the minus zero it already has
break;
}
d = DIST;
if ((opcode == OP_AABL) || (opcode == OP_SABL)) d = AbsWord(d);
if ((opcode == OP_SL) || (opcode == OP_SABL)) d = -d;
AddToAcc(0,d,1);
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
*CpuStepsUsed = 1+1+2+1
+(DrumAddr % 2) // using lower acc -> wait for even
+(bAccNegComplement ? 2:0); // acc sign change -> need to complement neg sum (two steps)
break;
case OP_RAU: // Reset and Add into Upper
case OP_RSU: // Reset and Subtract into Upper
case OP_AU: // Add to Upper
case OP_SU: // Substract from Upper
if ((opcode == OP_AU) && (ACC[1] == 0) && (ACC[0] == 0) && (AccNegativeZeroFlag) &&
(DIST == 0) && (DistNegativeZeroFlag)) {
// special case as stated in Operation manual 22(22-6060-2_650_OperMan.pdf), page 95
// Acc result on minus zero if acc contains minus zero and AU or AL with a drum
// location that contains minus zero
OV=0;
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: 0000000000 0000000000- (Minus Zero), OV: 0\n");
// acc keeps the minus zero it already has
break;
}
d = DIST;
if ((opcode == OP_RAU) || (opcode == OP_RSU)) ACC[1] = ACC[0] = 0;
if ((opcode == OP_SU) || (opcode == OP_RSU)) d = -d;
AddToAcc(d,0,1);
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
*CpuStepsUsed = 1+1+2+1
+((DrumAddr+1) % 2) // using upper acc -> wait for odd
+(bAccNegComplement ? 2:0); // acc sign change -> need to complement neg sum (two steps)
break;
// Multiply/divide
case OP_MULT: // Multiply
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Mult ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
sim_debug(DEBUG_DETAIL, &cpu_dev, "... by DIST: %06d%04d%c\n",
printfd);
if ((ACC[1] == 0) && (ACC[0] == 1) && (DIST == 0) && (DistNegativeZeroFlag)) {
// special case as stated in Operation manual 22(22-6060-2_650_OperMan.pdf), page 95
// Acc result on minus zero if a drum location that contains minus zero
// is multiplied by +1
OV = 0;
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Mult result ACC: 0000000000 0000000000- (Minus Zero), OV: 0\n");
// acc set to minus zero
ACC[1] = ACC[0] = 0;
AccNegativeZeroFlag = 1;
break;
}
*CpuStepsUsed = 0;
OV = 0;
neg = (DIST < 0) ? 1:0; if (AccNegative) neg = 1-neg;
d = AbsWord(DIST);
ACC[0] = AbsWord(ACC[0]);
ACC[1] = AbsWord(ACC[1]);
for(i=0;i<10;i++) {
n = ShiftAcc(1);
*CpuStepsUsed = *CpuStepsUsed + 2;
while (n-- > 0) {
AddToAcc(0, d, 1);
*CpuStepsUsed = *CpuStepsUsed + 18;
if (OV) break;
}
if (OV) break;
}
if (neg) {
ACC[0] = -ACC[0];
ACC[1] = -ACC[1];
}
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
// sequence chart for Multiply/Divide
// (1) (0..49) (1) (0/1) (20..200) (1)
// Enable Search Data to Wait Mult/Div Remove A
// Dist Data dist for even loop interlock
// (1) (1) (1) (0..49)
// Restart IA to AR Enable PR Search next
// Signal Inst
*CpuStepsUsed = 1+1+1+1
+(DrumAddr % 2) // wait for even
+*CpuStepsUsed; // i holds the number of loops done
break;
case OP_DIV: // Divide
case OP_DIVRU: // Divide and reset upper accumulator
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Div ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
sim_debug(DEBUG_DETAIL, &cpu_dev, "... by DIST: %06d%04d%c\n",
printfd);
if (DIST == 0) {
OV = 1;
sim_debug(DEBUG_DETAIL, &cpu_dev, "Divide By Zero -> OV set\n");
reason = STOP_OV; // divisor zero allways stops the machine
} else if (AbsWord(DIST) <= AbsWord(ACC[1])) {
OV = 1;
sim_debug(DEBUG_DETAIL, &cpu_dev, "Quotient Overflow -> OV set and ERROR\n");
reason = STOP_OV; // quotient overfow allways stops the machine
} else {
*CpuStepsUsed = 0;
OV = 0;
neg = (DIST < 0) ? 1:0; if (AccNegative) neg = 1-neg;
d = AbsWord(DIST);
ACC[0] = AbsWord(ACC[0]);
ACC[1] = AbsWord(ACC[1]);
for(i=0;i<10;i++) {
n = ShiftAcc(1);
ACC[1] = ACC[1] + n * D10;
*CpuStepsUsed = *CpuStepsUsed + 2;
while (d <= ACC[1]) {
AddToAcc(-d, 0, 0);
*CpuStepsUsed = *CpuStepsUsed + 18;
ACC[0]++;
}
}
if (neg) {
ACC[0] = -ACC[0];
ACC[1] = -ACC[1];
}
if (opcode == OP_DIVRU) {
ACC[1] = 0;
}
*CpuStepsUsed = 1+1+1+1
+(DrumAddr % 2) // wait for even
+*CpuStepsUsed + 40; // i holds the number of loops done
}
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Div result ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
break;
// shift
case OP_SLT: // Shift Left
case OP_SRT: // Shift Right
case OP_SRD: // Shift Right and Round
n = DA % 10; // number of digits to shift
if (opcode == OP_SRD) if (n == 0) n=10; // SRD 0000 means 10 sifts. SRT/SLT 0000 means no shifts
d = 0;
while (n-- > 0) {
d = ShiftAcc((opcode == OP_SLT) ? 1:-1);
}
if (opcode == OP_SRD) {
if (d <= - 5) AddToAcc(0,-1,1);
if (d >= 5) AddToAcc(0,+1,1);
OV = 0;
}
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
// sequence chart for shift
// (1) (0/1) (2) (1)
// Enable Wait Per Remove A
// Sh count for even shift interlock
// (0/1) (1) (1) (0..49)
// Restart IA to AR Enable PR Search next
// Signal Inst
*CpuStepsUsed = 1+1+1
+(DrumAddr % 2) // wait for even
+ 2*(DA % 10) // number of shifts done
+ ((opcode == OP_SRD) ? 1:0);
break;
case OP_SCT : // Shift accumulator left and count
n = 10 - DA % 10; // shift count (nine's complement of unit digit of DA)
neg = AccNegative; // save acc sign
ACC[0] = AbsWord(ACC[0]);
ACC[1] = AbsWord(ACC[1]);
if (n==10) n=0;
if (ACC[1] == 0) {
// upper acc is zero -> will have 10 or more shifts
ACC[1] = ACC[0];
ACC[0] = 10;
if (n) {
OV = 1; // overflow because n <> 0
} else {
if (Get_HiDigit(ACC[1]) == 0) OV = 1; // overflow because not just 10 shifts
}
} else if (Get_HiDigit(ACC[1]) != 0) {
// no shift will be done
ACC[0] = SetIA2(ACC[0], 0); // replace last two digits by 00
} else {
while (Get_HiDigit(ACC[1]) == 0) {
ShiftAcc(1); // shift left
if (n==10) {
OV = 1;
break;
}
n++;
}
ACC[0] = SetIA2(ACC[0], n); // replace last two digits by 00
}
AccNegativeZeroFlag = 0;
if (neg) {ACC[0] = -ACC[0]; ACC[1] = -ACC[1]; }
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
*CpuStepsUsed = 1+1+1
+(DrumAddr % 2) // wait for even
+ 2*(DA % 10); // number of shifts done
break;
// load and store
case OP_STL: // Store Lower in Mem
case OP_STU: // Store Upper in Mem
if ((ACC[0] == 0) && (ACC[1] == 0) && (AccNegativeZeroFlag)) {
DistNegativeZeroFlag = 1;
} else {
DistNegativeZeroFlag = 0;
}
DIST = (opcode == OP_STU) ? ACC[1] : ACC[0];
// sequence chart for store
// (1) (0/1) (1) (0..49) (1) (1) (1)
// Enable Wait L/U acc Search Store IA to AR Enable PR
// Dist for even to dist data data
// or odd
*CpuStepsUsed = 1+1+1+1+1+
+ (((opcode == OP_STU) ? DrumAddr:DrumAddr+1) % 2); // wait for odd/even depending on STU/STL opcode
break;
case OP_STD: // store distributor
*CpuStepsUsed = 1+1+1+1;
break;
case OP_STDA: // Store Lower Data Address
n = ((ACC[0] / D4) % D4); // get data addr xxDDDDxxxx from lower Acc
d = SetDA(DIST, n); // replace it in distributor
if ((d == 0) && ((DIST < 0) || ( (DIST == 0) && (DistNegativeZeroFlag) ))) {
// if dist results in zero but was negative or negative zero before replacing digits
// then it is set to minus zero
DistNegativeZeroFlag = 1;
} else {
DistNegativeZeroFlag = 0;
}
DIST = d;
*CpuStepsUsed = 1+1+1+1
+(DrumAddr % 2); // wait for even
break;
case OP_STIA: // Store Lower Instruction Address
n = (ACC[0] % D4); // get inst addr xxyyyyAAAA
d = SetIA(DIST, n); // replace it in distributor
if ((d == 0) && ((DIST < 0) || ( (DIST == 0) && (DistNegativeZeroFlag) ))) {
// if dist results in zero but was negative or negative zero before replacing digits
// then it is set to minus zero
DistNegativeZeroFlag = 1;
} else {
DistNegativeZeroFlag = 0;
}
DIST = d;
*CpuStepsUsed = 1+1+1+1
+(DrumAddr % 2); // wait for even
break;
case OP_LD: // Load Distributor
*CpuStepsUsed = 1+1+1+1;
break;
case OP_TLU: // Table lookup
{
char s[6];
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Search DIST: %06d%04d%c '%s'\n",
printfd,
word_to_ascii(s, 1, 5, DIST));
bUsingIAS = (AR >= 9000) ? 1:0;
if (bUsingIAS) {
AR = DA; // if TLU is searching on IAS, search starts at given addr
} else {
AR = (DA / 50) * 50; // set AR to start of drum band based on DA
}
AR--; n=-1;
while (1) {
AR++; n++;
if (0==IsDrumAddrOk(AR, vda_DS)) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "Invalid AR addr %d ERROR\n", AR);
reason = STOP_ADDR;
break;
}
if ((bUsingIAS == 0) && ((AR % 50) > 47)) continue; // skip addr 48 & 49 of band that cannot be used for tables
ReadAddr(AR, &d, NULL); // read table argument
if (AbsWord(d) >= AbsWord(DIST)) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Found %04d: %06d%04d%c '%s'\n",
AR, printfw(d,0),
word_to_ascii(s, 1, 5, d));
break; // found
}
}
// if tlu on ias, incr timing ring at end of instr execution
if (bUsingIAS) IAS_TimingRing = (IAS_TimingRing + 1) % 60;
// set the result as xxNNNNxxxx in lower acc
ACC[0] = SetDA(ACC[0], DA+n);
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Result ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
}
*CpuStepsUsed = 1+1+1+1+1+1
+(DrumAddr % 2) // wait for even
+ n; // number of reads to find the argument searched for
break;
// branch
case OP_BRD1: case OP_BRD2: case OP_BRD3: case OP_BRD4: case OP_BRD5: // Branch on 8 in distributor positions 1-10
case OP_BRD6: case OP_BRD7: case OP_BRD8: case OP_BRD9: case OP_BRD10:
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Check DIST: %06d%04d%c\n",
printfd);
d = DIST;
n = opcode - OP_BRD10; if (n == 0) n = 10;
while (--n > 0) d = d / 10;
d = d % 10;
if (d == 8) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "Digit is %d -> Branch Taken\n", (int32) d);
*bBranchToDA = 1; // IA (next instr addr) will be taken from DA. Branch taken
} else if (d == 9) {
// IA kept as already set. Branch not taken
sim_debug(DEBUG_DETAIL, &cpu_dev, "Digit is %d -> Branch Not Taken\n", (int32) d);
} else {
// any other value for tested digit -> stop
sim_debug(DEBUG_DETAIL, &cpu_dev, "Digit is %d -> Branch ERROR\n", (int32) d);
reason = STOP_ERRO;
break;
}
*CpuStepsUsed = 1+1
+ ((*bBranchToDA) ? 1:0); // one extra step needed if branch taken
break;
case OP_BRNZU: // Branch on Non-Zero in Upper
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
if (ACC[1] != 0) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "Upper ACC not Zero -> Branch Taken\n");
*bBranchToDA = 1;
}
*CpuStepsUsed = 1+1
+(DrumAddr % 2) // wait for even
+ ((*bBranchToDA) ? 1:0); // one extra step needed if branch taken
break;
case OP_BRNZ: // Branch on Non-Zero
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
if ((ACC[1] != 0) || (ACC[0] != 0)) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "Not Zero -> Branch Taken\n");
*bBranchToDA = 1;
}
*CpuStepsUsed = 1
+((DrumAddr+1) % 2) // wait for odd
+ ((*bBranchToDA) ? 1:0); // one extra step needed if branch taken
break;
case OP_BRMIN: // Branch on Minus
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
if (AccNegative) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "Is Negative -> Branch Taken\n");
*bBranchToDA = 1;
}
*CpuStepsUsed = 1+1
+ ((*bBranchToDA) ? 1:0); // one extra step needed if branch taken
break;
case OP_BROV: // Branch on Overflow
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Check OV: %d\n", OV);
if (OV) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "OV Set -> Branch Taken\n");
*bBranchToDA = 1;
}
*CpuStepsUsed = 1+1
+ ((*bBranchToDA) ? 1:0); // one extra step needed if branch taken
break;
// Card I/O
case OP_RD: // Read a card
bUsingIAS = (AR >= 9000) ? 1:0;
{
char s[6];
if (bUsingIAS == 0) {
AR = (DA / 50) * 50 + 1; // Drum Read Band is XX01 to XX10 or XX51 to XX60
}
reason = cdr_cmd(&cdr_unit[1], IO_RDS, AR);
if (reason == SCPE_NOCARDS) {
reason = STOP_CARD;
break;
} else if (reason != SCPE_OK) {
break;
}
// copy card data from IO Sync buffer to drum/ias
for (i=0;i<10;i++) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Read Card %04d: %06d%04d%c '%s'\n",
AR+i, printfw(IOSync[i],IOSync_NegativeZeroFlag[i]),
word_to_ascii(s, 1, 5, IOSync[i]));
if (bUsingIAS == 0) {
DRUM[AR + i] = IOSync[i];
DRUM_NegativeZeroFlag[AR + i] = IOSync_NegativeZeroFlag[i];
} else {
n = AR - 9000 + i;
IAS[n] = IOSync[i];
IAS_NegativeZeroFlag[n] = IOSync_NegativeZeroFlag[i];
if ((n % 10) == 9) break; // hit ias end of block, terminate read even if transfered less than 10 words
}
}
if (bUsingIAS) IAS_TimingRing = DA; // is using ias, set timing ring on instr completition
if (cdr_unit[1].u5 & URCSTA_LOAD) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Is a LOAD Card\n");
*bBranchToDA = 1; // load card -> next instr is taken from DA
}
}
// 300 msec read cycle, 270 available for computing
*CpuStepsUsed = 312; // 30 msec div 0.096 msec word time;
InterLockCount[IL_RD1] = 3120; // 300 msec for read card processing
break;
case OP_PCH: // Punch a card
bUsingIAS = (AR >= 9000) ? 1:0;
{
char s[6];
if (bUsingIAS == 0) {
AR = (DA / 50) * 50 + 27; // Drum Read Band is XX27 to XX36 or XX77 to XX86
}
// clear IO Sync buffer
for (i=0;i<10;i++) IOSync[i] = IOSync_NegativeZeroFlag[i] = 0;
// copy card data to IO Sync buffer from drum/ias
for (i=0;i<10;i++) {
if (bUsingIAS == 0) {
IOSync[i] = DRUM[AR + i];
IOSync_NegativeZeroFlag[i] = DRUM_NegativeZeroFlag[AR + i];
} else {
n = AR - 9000 + i;
IOSync[i] = IAS[n];
IOSync_NegativeZeroFlag[i] = IAS_NegativeZeroFlag[n];
IAS_TimingRing = i;
if ((n % 10) == 9) break; // hit ias end of block, terminate even if transfered less than 10 words
}
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Punch Card %04d: %06d%04d%c '%s'\n",
AR+i, printfw(IOSync[i],IOSync_NegativeZeroFlag[i]),
word_to_ascii(s, 1, 5, IOSync[i]));
}
reason = cdp_cmd(&cdp_unit[1], IO_WRS,AR);
if (reason == SCPE_NOCARDS) {
reason = STOP_CARD;
break;
} else if (reason != SCPE_OK) {
break;
}
if (bUsingIAS) IAS_TimingRing = (IAS_TimingRing + 1) % 60; // incr timing ring at end of pch
}
// 600 msec punch cycle, 565 available for computing
*CpuStepsUsed = 365; // 35 msec div 0.096 msec word time;
InterLockCount[IL_WR1] = 6250; // 600 msec for punch card processing
break;
// IAS - Immediate Access Storage
case OP_SET: // Set IAS Timing Ring
*CpuStepsUsed = 1+1+1;
break;
case OP_LDI: // Load IAS (from Drum)
n = TransferIAS("D->I", 0); // transfer drum to ias, end of ias block does not terminate transfer
*CpuStepsUsed = 1+1+1+n;
break;
case OP_STI: // Store IAS (to Drum)
n = TransferIAS("I->D", 0); // transfer ias to drum, end of ias block does not terminate transfer
*CpuStepsUsed = 1+1+1+n;
break;
case OP_LIB: // Load IAS Block (from Drum)
n = TransferIAS("D->I", 1); // transfer drum to ias, end of ias block does not terminate transfer
*CpuStepsUsed = 1+1+1+n;
break;
case OP_SIB: // Store IAS Block (to Drum)
n = TransferIAS("I->D", 1); // transfer ias to drum, end of ias block does not terminate transfer
*CpuStepsUsed = 1+1+1+n;
break;
// Index Register
case OP_AXA: // Add/Substract [with reset] to IRA
case OP_SXA:
case OP_RAA:
case OP_RSA:
n = IR[0];
if ((opcode == OP_RAA) || (opcode == OP_RSA)) n = 0;
if (DA >= 8000) {
ReadAddr(DA, &d, NULL);
i = (int) (d % D4);
} else {
i = DA;
}
n = n + (((opcode == OP_AXA) || (opcode == OP_RAA)) ? i : -i);
NormalizeAddr(&n);
sim_debug(DEBUG_DETAIL, &cpu_dev, "... IRA: %04d\n",
n);
IR[0] = n;
*CpuStepsUsed = 1+1+1;
break;
case OP_AXB: // Add/Substract [with reset] to IRB
case OP_SXB:
case OP_RAB:
case OP_RSB:
n = IR[1];
if ((opcode == OP_RAB) || (opcode == OP_RSB)) n = 0;
if (DA >= 8000) {
ReadAddr(DA, &d, NULL);
i = (int) (d % D4);
} else {
i = DA;
}
n = n + (((opcode == OP_AXB) || (opcode == OP_RAB)) ? i : -i);
NormalizeAddr(&n);
sim_debug(DEBUG_DETAIL, &cpu_dev, "... IRB: %04d\n",
n);
IR[1] = n;
*CpuStepsUsed = 1+1+1;
break;
case OP_AXC: // Add/Substract [with reset] to IRC
case OP_SXC:
case OP_RAC:
case OP_RSC:
n = IR[2];
if ((opcode == OP_RAC) || (opcode == OP_RSC)) n = 0;
if (DA >= 8000) {
ReadAddr(DA, &d, NULL);
i = (int) (d % D4);
} else {
i = DA;
}
n = n + (((opcode == OP_AXC) || (opcode == OP_RAC)) ? i : -i);
NormalizeAddr(&n);
sim_debug(DEBUG_DETAIL, &cpu_dev, "... IRC: %04d\n",
n);
IR[2] = n;
*CpuStepsUsed = 1+1+1;
break;
case OP_BMA: // Branch on IR Minus
case OP_BMB:
case OP_BMC:
i = ((opcode == OP_BMA) ? 0 : (opcode == OP_BMB) ? 1 : 2);
n = IR[i];
sim_debug(DEBUG_DETAIL, &cpu_dev, "... IR%c: %04d\n",
i+'A', n);
if (n<0) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "Is Negative -> Branch Taken\n");
*bBranchToDA = 1;
}
*CpuStepsUsed = 1+1
+ ((*bBranchToDA) ? 1:0); // one extra step needed if branch taken
break;
case OP_NZA: // Branch on IR Zero
case OP_NZB:
case OP_NZC:
i = ((opcode == OP_NZA) ? 0 : (opcode == OP_NZB) ? 1 : 2);
n = IR[i];
sim_debug(DEBUG_DETAIL, &cpu_dev, "... IR%c: %04d\n",
i+'A', n);
if (n==0) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "Is Zero -> Branch Taken\n");
*bBranchToDA = 1;
}
*CpuStepsUsed = 1+1
+ ((*bBranchToDA) ? 1:0); // one extra step needed if branch taken
break;
// floating point
case OP_FAD: // FP Add
case OP_UFA: // Unnormalized FP Add
case OP_FSB: // FP Sub
case OP_FAM: // FP Add Absolute value
case OP_FSM: // FP Sub Absolute
n = AddFloatToAcc((opcode == OP_FSB) || (opcode == OP_FSM), // subtract?
(opcode == OP_FAM) || (opcode == OP_FSM), // absolute value?
(opcode != OP_UFA) // normalize?
);
sim_debug(DEBUG_DETAIL, &cpu_dev, "... ACC: %06d%04d %06d%04d%c, OV: %d, DIST: %06d%04d%c\n",
printfa, OV, printfd);
*CpuStepsUsed = 1+1
+(DrumAddr % 2) // using upper acc -> wait for even
+2+2+2+1
+n; // Float Add steps
break;
case OP_FMP: // Float Multiply
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Mult ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
sim_debug(DEBUG_DETAIL, &cpu_dev, "... by DIST: %06d%04d%c\n",
printfd);
OV = 0;
if (((ACC[1] / 100) == 0) || ((DIST / 100) == 0)) {
// if any mantissa is zero -> multiply by zero -> result = 0
ACC[1] = ACC[0] = 0;
} else {
int exp = GetExp(DIST) + GetExp(ACC[1]) - 50;
neg = (DIST < 0) ? -1:1; if (AccNegative) neg = -neg;
ACC[1] = SetExp(AbsWord(ACC[1]), 0);
d = SetExp(AbsWord(DIST), 0);
// mult mantissas
for(i=0;i<10;i++) {
n = ShiftAcc(1);
*CpuStepsUsed = *CpuStepsUsed + 2;
while (n-- > 0) {
AddToAcc(0, d, 1);
*CpuStepsUsed = *CpuStepsUsed + 18;
if (OV) break;
}
if (OV) break;
}
MantissaRoundAndNormalizeToFloat(CpuStepsUsed, neg, exp);
}
sim_debug(DEBUG_DETAIL, &cpu_dev, "... FP Mult result ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
*CpuStepsUsed = 1+1+2+2+2+1+ *CpuStepsUsed
+(DrumAddr % 2); // wait for even
break;
case OP_FDV: // Float Divide
sim_debug(DEBUG_DETAIL, &cpu_dev, "... Div ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
sim_debug(DEBUG_DETAIL, &cpu_dev, "... by DIST: %06d%04d%c\n",
printfd);
OV = 0;
if ((DIST / 100) == 0) { // check mantissa for zero, not exponent
OV = 1;
sim_debug(DEBUG_DETAIL, &cpu_dev, "Divide By Zero -> OV set and ERROR\n");
reason = STOP_OV; // float divisor zero allways stops the machine
} else if ((ACC[1] / 100) == 0) {
// if dividend is zero -> result = 0
ACC[1] = ACC[0] = 0;
} else {
int exp = GetExp(ACC[1]) - GetExp(DIST) + 50;
neg = (DIST < 0) ? -1:1; if (AccNegative) neg = -neg;
ACC[1] = AbsWord(ACC[1]) / 100;
d = AbsWord(DIST) / 100;
// div mantissas
for(i=0;;i++) {
while (d <= ACC[1]) {
AddToAcc(-d, 0, 0);
*CpuStepsUsed = *CpuStepsUsed + 18;
ACC[0] = ACC[0] + 10; // add to second position of lower
}
if (i > 8) break;
if ((i == 8) && (Get_HiDigit(ACC[0]))) {exp++; break;}
n = ShiftAcc(1);
ACC[1] = ACC[1] + n * D10; // extra digit
*CpuStepsUsed = *CpuStepsUsed + 2;
}
ACC[1] = ACC[0];
MantissaRoundAndNormalizeToFloat(CpuStepsUsed, neg, exp);
}
sim_debug(DEBUG_DETAIL, &cpu_dev, "... FP Div result ACC: %06d%04d %06d%04d%c, OV: %d\n",
printfa,
OV);
*CpuStepsUsed = 1+1+2+2+16+2+1+ *CpuStepsUsed
+(DrumAddr % 2); // wait for even
break;
default:
reason = STOP_UUO;
break;
}
if ((reason == 0) && (OV) && (CSWOverflowStop)) reason = STOP_OV;
return reason;
}
// return 1 if must wait for storage
int WaitForStorage(int AR)
{
if ((AR >= 0) && (AR < DRUMSIZE)) {
if ((AR % 50) != DrumAddr) return 1; // yes, must wait for drum
} else if ((STOR) && (AR >= 9000) && (AR < 9060)) {
if (InterLockCount[IL_IAS] > 0) return 1; // yes, IAS was interlocked. Must wait until interlock is released
}
return 0;
}
t_stat
sim_instr(void)
{
t_stat reason;
int opcode, halt_cpu;
int bReadData, bWriteDrum, bBranchToDA;
int instr_count = 0; /* Number of instructions to execute */
const char * opname; /* points to opcode name */
int IA = 0; // Instr Address: addr of next inst
int DA = 0; // Data Address; addr of data to be used by current inst
int MachineCycle, CpuStepsUsed, il, WaitForInterlock;
/* How CPU execution is simulated
A cpu instruction is executed in real hw in several steps. Some os these steps involves waiting for rotating
drum to be positioned on requested addres (register AR). Other steps can involve waiting a Interlock to be released.
The execution of a complete instruction is called a machine cycle
User can select in real hw control panel to execute the instructions one by one. The execution is not done
on full instruction (a full cycle), but rather in instruction half-cycles: I-Cycle and D-Cycle.
During I-Cycle, the instruction is fetched from drum and decoded. During D-Cycle instruction is performed.
The simulator models this using the concept of MachineCycles, that groups several steps on opcode execution
SimH Real hw equivalent
machine cycle half cycle
0 I-Cycle WAIT FOR INSTR:
wait for drum to be positioned at address given by AR cpu register
1 I-Cycle FETCH INST:
read the drum to get instr to PR register,
decode PR as opcode, DA, IA,
apply index tags if needed, write back to PR
check if opcode must wait for interlock release
check if opcode reads data from drum
2 D-Cycle WAIT FOR DATA READ:
wait for interlock release if needed
wait for drum to be positioned at AR address if decoded opcode reads data from drum
3 D-Cycle EXEC:
get data from storage into DIST if needed
set interlock if needed
execute opcode operation
4 D-Cycle WAIT FOR DATA WRITE:
wait opcode excution time
wait for drum to be positioned at AR address if executed opcode writes data to drum
5 D-Cycle WRITEBACK:
if executed opcode writes data to drum, write DIST to drum
set AR=IA to read next instruction
*/
if (sim_step != 0) {
instr_count = sim_step;
sim_cancel_step();
}
reason = halt_cpu = 0;
MachineCycle = CpuStepsUsed = 0;
DrumAddr = 0;
CpuStepsUsed = 0;
if ((ProgStopFlag) &&
// if last inst was a programmed stop,
// and AR has not been changed (still contains the same value set by stop 01 opcode)
// gets instr to execute from IA instead of AR. This is to simulate the D-Cycle on stop opcode resume
((PR / D8) == 01) &&
(AR == ((PR / D4) % D4))) {
AR = (PR % D4);
ProgStopFlag = 0;
}
WaitForInterlock = 0; // clear interlocks
for (il=0;il<IL_array;il++) InterLockCount[il] = 0;
sim_cancel (&cpu_unit);
sim_activate (&cpu_unit, 1);
while (reason == 0) { /* loop until halted */
if (sim_interval <= 0) { /* event queue? */
reason = sim_process_event();
if (reason == SCPE_STOP) {
reason = 0; // if stop cpu requested, does not do it inmediatelly
halt_cpu = 1; // signal it so cpu is halted on end of current intr execution cycle
}
if (reason != SCPE_OK) {
break;
}
}
// housekeeping at beggining of inst execution cycle
if (MachineCycle == 0) {
// save current instr addr in pseudoregister IC
IC = AR;
// init current instr opcode in pseudoregister PROP
PROP = 0;
/* Only check for break points during actual fetch */
if (sim_brk_summ && sim_brk_test(IC, SWMASK('E'))) {
reason = STOP_IBKPT;
break;
}
// only check for ^E on fetch
if (halt_cpu) {
reason = SCPE_STOP;
break;
}
}
/* Main instruction fetch/decode loop */
sim_interval -= 1; /* count down */
// simulate the rotating drum: incr current drum position
DrumAddr = (DrumAddr+1) % 50;
// if any interlock set, decrease it
for (il=0;il<IL_array;il++) if (InterLockCount[il] > 0) InterLockCount[il]--;
// decrease pending to execute step intruction count
if (CpuStepsUsed > 0) CpuStepsUsed--;
// WAIT FOR INSTR
if (MachineCycle == 0) {
if (HalfCycle == 2 ) { // if D-Half should start
HalfCycle = 1; // bump half cycle to exec I-Half on next scp step
instr_count = 1; // break at the end of D-half execution
MachineCycle = 3;
continue;
}
// should wait for storage to fetch inst?
if (FAST == 0) if (WaitForStorage(AR)) continue; // yes
// init inst execution
CpuStepsUsed = 0;
MachineCycle = 1;
}
// FETCH INST
if (MachineCycle == 1) {
// get current intruction from storage, save current instr addr in IC
IC = AR;
if (0==ReadAddr(AR, &PR, NULL)) {
reason = STOP_ADDR;
goto end_of_cycle;
}
// decode inst
opname = DecodeOpcode(PR, &opcode, &DA, &IA);
sim_debug(DEBUG_CMD, &cpu_dev, "Exec %04d: %02d %-6s %04d %04d %s%s\n",
IC, opcode, (opname == NULL) ? "???":opname, DA, IA,
((AR >= MAXDRUMSIZE) || (DRUM_Symbolic_Buffer[AR * 80] == 0)) ? "" : " symb: ",
(AR >= MAXDRUMSIZE) ? "" : &DRUM_Symbolic_Buffer[AR * 80]);
PROP = (uint16) opcode;
if (opname == NULL) {
reason = STOP_UUO;
goto end_of_cycle;
}
// if DA or IA tagged, modify DA or IA to remove tag and set the developed address in PR
if (STOR) {
int nIndexsApplied;
nIndexsApplied = ApplyIndexRegister(&DA) + ApplyIndexRegister(&IA);
if (nIndexsApplied > 0) {
CpuStepsUsed += nIndexsApplied;
PR = (t_int64) opcode * D8 + (t_int64) DA * D4 + (t_int64) IA;
sim_debug(DEBUG_CMD, &cpu_dev, "Exec %04d: %02d %-6s %04d %04d %s\n",
IC, opcode, (opname == NULL) ? "???":opname, DA, IA,
" (developed addr)");
}
}
AR = DA; // allways trasnfer DA to AR even if drum will be not read. This is why
// all opcodes must have a valid DA address even if not used to read drum (eg SRT 0003 to shift)
// simulates the machine working on half cycles
if (HalfCycle == 1) { // if I-Half finished, about to exec D-Half
HalfCycle = 2; // bump half cycle to exec D-Half on next scp step
reason = SCPE_STEP; // then break beacuse I-Half finished
break;
}
bReadData = (base_ops[opcode].opRW & opReadDA) ? 1:0;
// check if opcode should wait for and already set interlock
WaitForInterlock = base_ops[opcode].opInterLock;
MachineCycle = 2;
}
// WAIT FOR DATA READ
if (MachineCycle == 2) {
// should wait to exec the inst (the address untagging) ?
if (FAST == 0) if (CpuStepsUsed > 0) continue; // yes
// should wait for interlock release for opcode execution?
if (WaitForInterlock) {
if (FAST == 0) if (InterLockCount[WaitForInterlock] > 0) continue; // interlock makes execution wait
InterLockCount[WaitForInterlock] = 0; // clear interlock
WaitForInterlock = 0;
}
// should wait for storage to fetch data?
if (bReadData) {
if (FAST == 0) if (WaitForStorage(AR)) continue; // yes
}
MachineCycle = 3;
}
// EXEC
if (MachineCycle == 3) {
// decode again PR register to reload internal register DA, IA, AR again. Needed if we are executing half cycles
opname = DecodeOpcode(PR, &opcode, &DA, &IA);
AR = DA;
if (opname == NULL) {
reason = STOP_UUO;
goto end_of_cycle;
}
// even if no data is fetched, DA addr must be a valid one for this opcode
if (0==IsDrumAddrOk(AR, base_ops[opcode].validDA)) {
sim_debug(DEBUG_DETAIL, &cpu_dev, "... %04d: Invalid addr ERROR\n", AR);
reason = STOP_ADDR;
goto end_of_cycle;
}
// get data from if needed
bReadData = (base_ops[opcode].opRW & opReadDA) ? 1:0;
if (bReadData) {
ReadAddr(AR, &DIST, &DistNegativeZeroFlag);
sim_debug(DEBUG_DATA, &cpu_dev, "... Read %04d: %06d%04d%c\n",
AR, printfd);
}
bWriteDrum = (base_ops[opcode].opRW & opWriteDA) ? 1:0;
reason = ExecOpcode(opcode, DA,
&bBranchToDA,
DrumAddr, &CpuStepsUsed);
if (reason != 0) goto end_of_cycle;
if (bBranchToDA) IA = DA;
MachineCycle = 4;
}
// WAIT FOR DATA WRITE
if (MachineCycle == 4) {
// should wait to exec the inst (opcode execution) ?
if (FAST == 0) if (CpuStepsUsed > 0) continue; // yes
// should wait for storage to store data?
if (bWriteDrum) {
if (FAST == 0) if (WaitForStorage(AR)) continue; // yes
}
MachineCycle = 5;
}
// WRITEBACK
if (MachineCycle == 5) {
if (bWriteDrum) {
sim_debug(DEBUG_DATA, &cpu_dev, "... Write %04d: %06d%04d%c\n",
AR, printfd);
if (0==WriteAddr(AR, DIST, DistNegativeZeroFlag)) {
reason = STOP_ADDR;
goto end_of_cycle;
}
}
// set AR to point to next instr
AR = IA;
// no more machine cycles
}
end_of_cycle:
if (instr_count != 0 && --instr_count == 0) {
if (reason == 0) {
IC = AR;
// if cpu not stoped (just stepped) set IC so next inst to be executed is shown.
// if cpu stopped because some error (reason != 0), does not advance IC so instr shown is offending one
reason = SCPE_STEP;
break;
}
}
MachineCycle = 0; // ready to process to next instr
} /* end while */
// flush 407 printout
if ((cdp_unit[0].flags & UNIT_ATT) && (cdp_unit[0].fileref)) {
fflush(cdp_unit[0].fileref);
}
/* Simulation halted */
return reason;
}
/* Reset routine */
t_stat
cpu_reset(DEVICE * dptr)
{
ACC[0] = ACC[1] = DIST = 0;
PR = AR = OV = 0;
ProgStopFlag = 0;
AccNegativeZeroFlag = 0;
DistNegativeZeroFlag = 0;
IC = 0;
IAS_TimingRing = 0;
IR[0] = IR[1] = IR[2] = 0;
sim_brk_types = sim_brk_dflt = SWMASK('E');
return SCPE_OK;
}
/* Memory examine */
t_stat
cpu_ex(t_value * vptr, t_addr addr, UNIT * uptr, int32 sw)
{
t_int64 d;
int NegZero;
t_value val;
if (0==ReadAddr(addr, &d, &NegZero)) {
return SCPE_NXM;
}
if (vptr != NULL) {
if (NegZero) {
val = NEGZERO_value; // val has this special value to represent -0 (minus zero == negative zero)
} else {
val = (t_value) d;
}
*vptr = val;
}
return SCPE_OK;
}
/* Memory deposit */
t_stat
cpu_dep(t_value val, t_addr addr, UNIT * uptr, int32 sw)
{
t_int64 d;
int NegZero;
if (val == NEGZERO_value) {
d = 0;
NegZero = 1;
} else {
d = val;
NegZero = 0;
}
if (0==WriteAddr(addr, d, NegZero)) {
return SCPE_NXM;
}
return SCPE_OK;
}
t_stat
cpu_set_size(UNIT * uptr, int32 val, CONST char *cptr, void *desc)
{
int mc = 0;
uint32 i;
int32 v;
v = val >> UNIT_V_MSIZE;
if (v == 0) {v = 1000;} else
if (v == 1) {v = 2000;} else
if (v == 2) {v = 4000;} else v = 0;
if ((v <= 0) || (v > MAXDRUMSIZE))
return SCPE_ARG;
if (v < 4000) {
for (i = v; i < MAXDRUMSIZE; i++) {
if ((DRUM[i] != 0) || (DRUM_NegativeZeroFlag[i] != 0)) {
mc = 1;
break;
}
}
}
if ((mc != 0) && (!get_yn("Really truncate memory [N]? ", FALSE)))
return SCPE_OK;
cpu_unit.flags &= ~UNIT_MSIZE;
cpu_unit.flags |= val;
cpu_unit.capac = 9990 + (v / 1000);
for (i=0;i<MAXDRUMSIZE * 80;i++)
DRUM_Symbolic_Buffer[i] = 0; // clear drum symbolic info
for (i = DRUMSIZE; i < MAXDRUMSIZE; i++)
DRUM[i] = DRUM_NegativeZeroFlag[i] = 0;
for(i = 0; i < 60; i++) IAS[i] = IAS_NegativeZeroFlag[i] = 0;
return SCPE_OK;
}
t_stat
cpu_help (FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr) {
fprintf (st, "These switches are recognized when examining or depositing in CPU memory:\r\n\r\n");
fprintf (st, " -c examine/deposit characters, 5 per word\r\n");
fprintf (st, " -m examine/deposit IBM 650 instructions\r\n\r\n");
fprintf (st, "The memory of the CPU can be set to 1000, 2000 or 4000 words.\r\n\r\n");
fprintf (st, " sim> SET CPU nK\r\n\r\n");
fprintf (st, " sim> SET CPU StorageUnit enables IBM 652 Storage Unit\n");
fprintf (st, " sim> SET CPU NoStorageUnit disables IBM 652 Storage Unit\n\n");
fprint_set_help(st, dptr);
fprint_show_help(st, dptr);
return SCPE_OK;
}
const char * cpu_description (DEVICE *dptr) {
return "IBM 650 CPU";
}