[Simh] Hardware fidelity in the VAX family simulators

[Robert Armstrong]

>I haven't found microcode sources or listings for the 750, 730,
> MicroVAX I, or 8600, for example. 

  FWIW, the 725/730 was somewhat unique in that the micro store was entirely RAM.  All of the microcode was loaded by the CFE at power on and none was in ROM.  Also, the 730 micro engine was based on industry standard 29xx family bit slice parts.  It was a little like the 11/60 in that it was easy, in theory at least, to write custom microcode.  I've heard that certain customized versions of the 730 microcode were produced for special needs, and that DEC even supported this with some development tools, but I've never seen any such thing in the wild.

  So, if anyway if anybody does find the sources or development tools for the 730/725 microcode, I'd love to see a copy.

  Back to Bob's topic, I do have a running 730 system that could be powered on more or less any time.  I'm willing to run tests if anybody needs to experiment with the behavior of real hardware.  It's even on HECnet, so I could make remote access available.

Bob Armstrong