[Simh] Multiprocessor VAX simulator

Sergey Oboguev oboguev at yahoo.com
Sat Nov 10 15:38:55 EST 2012

VAX MP is a derivative variant of SIMH VAX simulator capable to execute OpenVMS 
(VAX/VMS) in true SMP mode on multiprocessor host machines, including modern 
commodity multicore/hyperthreaded PCs and Macs.

Initial release of VAX MP supports Intel x86 and x64 processors based machines 
as host hardware platform with Windows, Linux and OS X as host operating 

The number of VAX MP virtual processors is limited to the number of host 

simultaneous execution units (logical CPUs). For example, PC with quad-core i7 
processor has hyperthreaded cores and would allow to run VAX MP instance 
with up to 8 virtual processors. 

VAX MP had been tested to OpenVMS VAX theoretical limit of 32 processors.

VAX MP is an architectural simulator. The focus is on OpenVMS SMP capability, 
rather than simulation of specific historical hardware. Accordingly VAX MP does 
not attempt to simulate any historically existing VAX multiprocessor model, 
although it may be used as a stepping stone towards further development of such 
a simulator. Instead VAX MP simulates a multiprocessor variant of MicroVAX 3900,
a machine that never historically existed, but complies generic VAX architecture 

and runs OpenVMS in SMP mode.

VAX MP is currently downloadable from my pesonal web page that hosts source 
documentation, prebuilt binaries and screenshots.


Those nostalgic for "real iron" may also view photographs of a session using 
VT320 connected via DECserver 200 to a VAXcluster of two VAX MP nodes, each with 

8 processors, under heavy cluster IO traffic.

Important legal notice: 

Although on a purely technical level VAX MP does not require VMS SMP extension 
license to run and OpenVMS runs fully functional in SMP mode on VAX MP without 
prompting for SMP extension license, however from the legal standpoint running 
VMS in SMP mode may require a license for VMS SMP extension. Whether such 
license is needed for hobbyist use is a gray area. Please be sure to consult 
"Legal information notice B" in "VAX MP OpenVMS User Manual" for more 
information regarding licensing situation. I personally do have SMP extension 
license legally sufficient to cover VAX MP development and testing "in the 
white", but your mileage may vary. I am unable to advise whether hobbyist use of 

OpenVMS VAX in multiprocessor mode would require SMP extension license.

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