a5feaf2815
- Add 1752 Drum support. Allow shared subroutines across interrupt levels. - Document and add sample scripts for customizing MSOS5.
215 lines
9.4 KiB
Text
215 lines
9.4 KiB
Text
CDC 1700 Simulator
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==================
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1. Overview.
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The CDC 1700 was a 16-bit mini-computer produced by the Control Data
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Corporation with deliveries beginning in May 1966.
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2. Hardware
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This simulator provides support for a subset of available peripherals,
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mostly from the early period of its release:
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device name Hardware
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CPU 1714 CPU with 4KW, 8KW, 16KW or 32KW of memory
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1705 Multi-Level Interrupt and Direct Storage Access
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Bus
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Optional extensions:
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64KW of memory with indirect addressing changes
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Character addressing option
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RTC 10336-1 Real-time clock
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Default tick interval is 10mSec, can be changed with
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"set rtc rate=<rate>" command, where <rate> is
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{1usec|10usec|100usec|1msec|10msec|100msec|1second}.
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[ Equipment address: 0xD]
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DCA Data channels providing DMA access to non-DMA
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DCB peripherals. The configuration is currently fixed
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DCC with DCA providing access to the magtape controller
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if it is configured as a 1732-A.
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TTI 1711-A Half-duplex console terminal.
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TTO [Equipment address: 0x1, Station address: 1]
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PTR 1721-A Paper tape reader
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[Equipment address: 0x1, Station address: 2]
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PTP 1723-A Paper tape punch
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[Equipment address: 0x1, Station address: 4]
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MT 1732-A or 1732-3 Magtape controller, 3 9-track drives
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(MT0 - MT2) and 1 7-track drive (MT3). The type of
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the controller may be changed using the command
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"set mt type={1732-A|1732-3}". The 1732-A controller
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supports 200, 556 and 800 BPI on the 9 track drives
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and allows DMA access via a 1706 Buffered Data
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Channel (device DCA). The 1733-3 controller supports
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556, 800 and 1600 BPI on the 9 track drives and
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includes DSA (DMA) access built into the controller.
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Access via a 1706 Buffered Data Channel is not
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available.
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[Equipment address: 0x7]
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LP 1740 or 1742-30 Line printer (Upper case only). The
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type of the printer may be changed with the command
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"set lp type={1740|1742}; The 1742-30 is compatible
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with the 1742-120 but not allow the print train
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configuration to be loaded by software.
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[Equipment address: 0x4]
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DP 1738-B Disk pack controller. Supports up to 2
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disk pack drives:
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853 drive - 3072000 bytes
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854 drive - 6236160 bytes
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[Equipment address: 0x3]
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CDD 1733-2 Cartridge disk pack controller. Supports up to
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4 cartridge disk drives. Each drive supports a fixed
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and a removeable disk:
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856-2 drive - 2260608 bytes
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856-4 drive - 4543488 bytes
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[Equipment address: 0x3]
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DRM 1752 Drum memory controller with 64 - 1024 tracks of
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drum memory (each track is 3072 words).
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[Equipment address: 0x2]
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Notes:
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DP and CDD use the same equipment address so only 1 of them may be
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enabled (default is for CDD to be enabled).
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Both controllers use checkwords (CRC) for validating the consistency
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of the data stored on disk. The DP controller exports a single status
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bit indicating whether the checkword is valid or not (the simulator
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always sets this to valid). The CDD controller also exports a single
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status bit which is handled in the same way as the DP controller.
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It also makes the actual checkword value available. The simulator
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always returns a checkword value of 0 so any attempt to verify the
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checkword (such as some diagnostics) will fail.
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3. Loading Software
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The simulator implements 2 mechanisms for loading software which
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follow the hardware mechanisms provided by the real hardware:
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- Magtape bootstraps toggled in through the front panel
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- Autoload mechanism for disk drives
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3.1 Magtape bootstraps
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Software may be loaded from a magtape drive by using the SIMH command
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"boot mtx" (currently only drive 0 is supported) which loads an appropriate
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bootstrap into memory. This bootstrap loads the next record from the tape and
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starts execution of the loaded code.
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3.1.1 Default bootstrap
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The default bootstrap is used for loading operating system distribution
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tapes and is loaded at location 0. Register A is set according to the amount
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os memory installed in the system:
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- 0x5000 if 32KW or greater is installed
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- 0x4000 if 24KW or 28KW is installed
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- 0x2000 if less than 24KW is installed
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3.1.2 SMM17 bootstrap
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SMM17 is the System Maintenance Monitor and uses a tailored bootstrap
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which is loaded into the highest addressed 4KW module installed in the system.
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The following switches may be used with the "boot" command for special
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handling:
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-S load the SMM17 bootstrap rather than the default bootstrap
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-D configure the SMM17 bootstrap to use Buffered Data Channel #1
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to access the magtape controller
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3.2 Disk autoload
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The autoload mechanism loads track 0 from logical drive 0 of a disk or
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drum controller to memory location 0, it does not start execution of the loaded
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code (some of the diagnostics code relies on this). DP, CDD and DRM controllers
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support the autoload command ("autoload dp", "autoload cdd" or "autoload drm")
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which is normally followed by a "run 0" command to start execution of the
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loaded code.
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4. Operating The Simulator
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4.1 CPU
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The control panel of a physical CDC 1700 system has a number of
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switches which control the operation of the CPU. In the simulator, these
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switches can be turned on and off with the commands "set cpu xxx" and
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"set cpu noxxx". By default, all the switches are off.
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4.1.1 Selective Stop (set cpu sstop/nosstop)
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The Selective Stop switch controls how the "Selective Stop (SLS)"
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instruction executes. If the switch is Off, SLS executes as a no-operation.
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If the switch is On, SLS executes as a halt instruction. Continuing after
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the halt causes the CPU to execute the instruction following SLS.
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4.1.2 Selective Skip (set cpu sskip/nosskip)
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The Selective Skip switch controls how the SWS and SWN skip
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instruction execute. SWS will skip if the switch is set and SWN will skip if
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the switch is not set. Both the Selective Stop and Selective Skip switches
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are used extensively to control execution of the System Maintenance Monitor.
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4.1.3 Protect (set cpu protect/noprotect)
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Each word of memory on the CDC 1700 series consists of 18-bits; 16-bits
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of data/instructions, a parity bit (which is not implemented in the simulator)
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and a program protect bit. If the Protect switch is Off, any program may
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reference any word of memory. If the Protect switch is On, there are a set of
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rules which control how memory accesses work and when to generate a program
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protect violation - see one of the 1700 reference manuals on bitsavers.org for
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exact details.
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The simulator fully implements CPU protect mode allowing protected
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operating systems such as MSOS 5 to execute. It does not support peripheral
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protect operation which allows unprotected programs to directly access
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some unprotected peripherals.
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Operating systems and other programs which run with the Protect
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switch on usually start up with the Protect switch off, manipulate the
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protect bits in memory (using the CPB/SPB instructions) and then ask the
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operator to set the Protect switch on.
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4.2 Teletype
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The console teletype on some of the earlier models of the CDC 1700
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series had a "Manual Interrupt" button so that the operator could get the
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attention of the operating system. Later models used a display terminal and
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used the "Control+G" key conbination to generate a Manual Interrupt. The
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Simulator follows this convention of using the "Control+G" key combination.
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The actual key combination may be changed by issuing the command
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"deposit tti intrkey xx" where xx is desired key code in hex.
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5. Software
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There is some software available at bitsavers.org in the
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bits/CDC/1700_Cyber18 directory, see CDC1700-Diagnostics.txt and
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CDC1700-MSOS.txt for more details.
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6. Cyber-18
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The CDC 1700 later morphed into the Cyber-18 series. This series
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included an enhanced instruction set using unused bits from the 1700
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instruction encoding. The simulator can detect these instructions and can be
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configured to stop if it tries to execute such an instruction
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(set cpu debug=enhanced). Due to a lack of detailed documentation it it
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unlikely that the enhanced instruction set will ever be completely implemented.
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