[Simh] some performance issues

[Zane Healy]

I have to wonder if a lightweight Linux disto, that has been locked down, running on a Core i7 might not give better SIMH performance.  My *old* i7 ESXI box provides a faster “VAX” than my VAXstation 4000/60.

What is the reason for running on Itanium?

Zane



> On Mar 6, 2019, at 1:57 AM, Pontus Pihlgren <pontus at Update.UU.SE> wrote:
> 
> Hi
> 
> I'm having trouble understanding your question. Are 
> you comparing CPU-time of a real VAX(which model?) to 
> emulated CPU-time on an Itanium machine(which one?).
> 
> Emulation will have an associated overhead. If you 
> are compareing a fast VAX to an emulation on a slow 
> Itanium... well, Itanium is hard to optimize for.
> 
> /P
> 
> On Tue, Mar 05, 2019 at 03:13:53PM +0100, gérard Calliet wrote:
>> Hello,
>> 
>> Again I have some performance issues with simh.
>> 
>> I built it  on OpenVMS Itanium. It runs on a process with enought
>> memory, it takes 1 of the 8 CPU Itanium with 100%, no page faults,
>> and 100 BIO by second.
>> 
>> On the emulated VAX we are running processes CPU intensive (old Ada
>> compiler), they take 100% of the CPU, also very few page fault, very
>> few IO.
>> 
>> And the CPU time is about 2 or 3 times the CPU time on the hardware,
>> and so elapsed time 3 or 4 times. (For my understanding, it is
>> difficult to think the same stream of instructions can use different
>> CPU times between hardware and SIMH).
>> 
>> Where can I do something to improve performance? Are there
>> parameters (or constant in compilation) in SIMH which could help?
>> And the specific context is processes doing almost only CPU
>> computing.
>> 
>> 
>>>>>> my configuration, and what commit I use
>> on error continue
>> load -r ka655x.bin
>> attach NVR ka655.nvr
>> set cpu 512m
>> set cpu conhalt
>> set RL disable
>> set LPT disable
>> set TQ disable
>> set -L rq0 rauser=18000000
>> attach rq0 datauser2.dsk
>> set xq mac=08-00-2B-3C-96-75
>> attach xq eth0
>> dep bdr 0
>> b cpu
>> 
>> 
>> $ run vax-i64
>> MicroVAX 3900 simulator V4.0-0 Beta        git commit id: 8810571d
>> sim>
>> 
>> 
>>>>>>>>>>>>>>>> 
>> 
>> Thanks,
>> 
>> Gérard Calliet
>> 
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