User manual

Introduction
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accommodate NUMA factors. Any significant NUMA factors would cause inefficient process-to-resource
allocation within the guest operating system and, most importantly, jeopardize guest operating system
stability; for this reason host systems with significant NUMA factors are not currently supported.
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However it might be possible to run VAX MP on high-NUMA system as long as VAX MP is allocated to a
partition with low intra-region NUMA factor.
Host software requirements
Current release of VAX MP runs on Windows, Linux and OS X. Refer to system-specific sub-sections
below for information regarding particular host operating system. Note that this document does not
attempt to substitute general SIMH documentation and does not seek to cover those VAX MP features
and requirements that are not specific to VAX MP and are identical with general version of SIMH.
Some host operating systems allow both 32-bit and 64-bit build of VAX MP. Depending on OpenVMS
workload, sometimes 32-bit build may be slightly more performant than 64-bit build and sometimes vice
versa. On average, there is a preliminary feeling that 32-build when available is slightly more performant
than 64-build, within few percent of difference, albeit more extensive metrics is required yet for proper
comparison.
Running 32-bit build of VAX MP under 64-bit Windows is trivial.
Running 32-bit build of VAX MP under 64-bit Linux had not been attempted.
It may be possible but would require installation and configuration of 32-bit (ia32) environment.
Network-enabled version of VAX MP built with SHR option would also require 64-bit to 32-bit bridging
library for
libpcap. However if VAX MP is built with statically linked libpcap (build option NET), then
bridging library is not needed and 32-build of VAX MP might possibly be able to run under 64-bit version
of Linux. To reiterate, this have not been tried.
On OS X, VAX MP provides only 64-bit executable.
Host networking configuration
VAX MP provides the same networking support as regular SIMH, including uniprocessor SIMH VAX.
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Besides inefficient process-to-resource allocation high NUMA factors may distort the calibration of OpenVMS
timing loops and cause OpenVMS to bugcheck because of SMP timeouts. The latter can be partially adjusted either
by increasing the value of OpenVMS SYSGEN parameters SMP_SPINWAIT and SMP_LNGSPINWAIT or equivalent
increase of SMT slow-down factor supplied via VAX MP SIMH console/script command CPU SMT. Timeouts in some
of OpenVMS interlocked queue operations retry loops can be enlarged by increasing SYSGEN parameter
LOCKRETRY. However many of OpenVMS interlocked queue retry operations use large but fixed retry count of
900,000 iterations that is not extensible by increase in LOCKRETRY.