The commands which operate through run_cmd (GO, STEP, CONTINUE, BOOT, RUN) will all exit with a status which is NOT SCPE_OK. Most of the exit status values will be 100% normal and not indicative of a true error, so producing error message context is not necessary or desired.
265. PROBLEM: Compiling the HP simulator for 64-bit addressing produces many
conversion warnings.
OBSERVATION: Compiling the simulator and defining USE_INT64 and USE_ADDR64
with implicit conversion warnings enabled reveals a number of places where
assumptions were made that addresses would always be 32 bits. This is a
reasonable assumption, as there are no devices (CPU or peripherals) that
can handle gigabyte addressing. Still, many of these assumptions are not
necessary, and some future peripheral simulator may exceed this limit.
CAUSE: Future expansion to 64-bit addressing was not envisioned.
RESOLUTION: Modify source files to ensure that "t_addr" and "t_value"
types are used instead of "uint32" and "int32" types where addressing and
data values may be 64 bits. Also ensure that valid conversions to smaller
sizes use explicit casts.
266. PROBLEM: BOOT devices require a duplicate S-register declaration.
OBSERVATION: All of the peripheral devices that support the BOOT command
set the select code and other parameters into the S register during the
boot process. This direct register access requires an external declaration
that duplicates the one in the full CPU declarations file (hp2100_cpu.h).
A better method that avoids the duplicate declaration would be for the
"ibl_copy" routine to modify the S register on behalf of the caller.
CAUSE: Poor original implementation.
RESOLUTION: Modify "ibl_copy" (hp2100_cpu.c) to take two additional
parameters that clear and set bits, respectively, in the S register on
behalf of the caller. Modify the boot routines for the CPU, DA, DP, DQ,
DR, DS, IPL, MS, and PTR devices to use the new parameters instead of
modifying the S register directly.
- Provide a sim_islower(), sim_isalpha(), sim_isprinit(), sim_isdigit(), sim_isgraph(), sim_isalnum() which make sure that the character being examined as an unsigned char.
- Ignore a UTF_BOM sequence at the beginning of command files.
- Provide a sim_isspace() which makes sure that isspace only considers the character being examined as an unsigned char.
The commands which operate through run_cmd (GO, STEP, CONTINUE, BOOT, RUN) will all exit with a status which is NOT SCPE_OK. Most of the exit status values will be 100% normal and not indicative of a true error, so producing error message context is not necessary or desired.
The native VMB.EXE program historically supported a Boot Block oriented
boot if Bit 3 of the parameter register (R5) was set when VMB was invoked.
This Boot Block boot operation reads sector 0 into memory and starts
execution at offset 2 of the data block in memory.
When portitions of VMB were migrated into ROM to support the earliest
MicroVAX system (MicroVAX I) and all subsequent ROM based VMB versions
the concept of Boot Block booting was extended in these ROM VMB
implementations. The change in boot block booting functionality included
several features:
1) If a normal boot attempt to a device failed (due to VMB not being
able to locate a secondary bootstrap program), a boot block boot is
automatically attempted. If the Bit 3 of R5 was set, then the
initial search for a secondary boot block was avoided and a boot
block boot was immediately attempted.
2) When performing a boot block boot, the sector 0 contents are examined
and if these contents conform to the pattern defined for ROM based
(PRA0) booting, the ROM format Offset, Size, and Starting address
information is used directly by VMB to load a program into memory
and control is transferred to that program. If the contents of
sector 0 do not fit the pattern required for ROM based booting, then
the code in sector 0 is executed directly starting at offset 2,
the same as was originally done with the non ROM based VMB versions.
Note that this extended behavior allows sector 0 to contain very little
information and quite possibly no actual boot code.
Developers of alternate operating systems for VAX computers noticed the ROM
based boot block behavior and changed their installation media AND the disk
structures to only provide the minimal boot information required on the
systems with VMB installed in ROM.
Since, when this active development of these alternate operating systems for
VAX computers was happening, the vast majority of development and new system
deployments were to hardware which had ROM base VMB, no one noticed that
older systems which booted with the non ROM based VMB could no longer boot
from new install media or disks formatted with these operating systems.
This patch addeds the ROM based VMB boot block boot functionality to the
original dynamically loaded VMB.EXE used by the older systems to boot.
The patch overwrites some VMB code which exists to support NVAX(1302) and
Neon-V(1701) systems. If simh simulators for these systems are ever built
an alternate location must be found to accomodate this extended logic
