Looking for a small fast VAX development machine

Jerome H. Fine jhfinedp3k at compsys.to
Sun Feb 21 17:37:55 CST 2016

 >Holm Tiffe wrote:

>>Jerome H. Fine wrote:
>>>Holm Tiffe wrote:
>>>>Ben Sinclair wrote:
>>>>I was just looking up VAXstations the other day on eBay. I checked
>>>>again now for 4000's, and the prices seem crazy. Is there something
>>>>particularly special about them, or is it just the usual eBay
>>>..that are the smallest and fastest VAXen so it is not so unlikely
>>>that the prices are crazy...
>>>Why you don't use an simulator (E11, simh) for the job?
>>That sounds like a good idea to use SimH for the VAXstation.  However,
>>I suspect that E11 (Ersatz-11) would be a bit difficult to use to emulate a
>>VAXstation since E11 is exclusively for the PDP-11.
>>As for the individual who mentioned the speed of an emulator, I have used
>>both SimH and Ersatz-11 on a 750 MHz Pentium III.  SimH probably runs
>>at about the speed of a PDP-11/93, probably even faster.  However, Ersatz-11
>>runs 15 times as fast for CPU speed and about 100 times as fast for hard 
>>disk I/O.
>>On a 2.83 GHz Q9550, Ersatz-11 ran about 100 times the speed of a PDP-11/93
>>for the CPU and hard disk I/O was probably about 200 times as fast. As just
>>one example, on a real DEC PDP-11/93 with ESDI hard drives, it took about
>>4 minutes to copy about 32 MB from one physical hard drive to a different
>>physical hard drive.  On the Q9550, it took less than 1 second.  I was using
>>RT-11 in all cases.  I would assume that an I7 CPU would be somewhat faster,
>>but maybe someone else has some benchmarks.
>Yes. Jerome he is right, he ist not intrrested in your great numbers since
>hi want to emulate not a PDP11, but a VAX.
But I suspect that there might be a few individuals who are also 
interested in
emulating the PDP-11, so those "great numbers" might be helpful to them.

The other point to emphasize is that SimH does a great job of emulation,
but is not the fastest application.  If someone was interested in producing
code which executes in the manner in which Ersatz-11 does it for the
PDP-11, but doing so for a VAX emulation, the results might be spectacular.

Jerome Fine

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