[Simh] Alpha simulator performance

[Dan Gahlinger]

NT is not VMS or a reimplementation of it.i wouldnt even say there's vms code in there.there can't be, VMS was never that bad.
NT crashed all over the place, it was unstable, it was horrifically bloatedand all sorts of other nasty things.on top of that it's really only a single-user system.
you could have hundreds of users simultaneously on a vax750 and it wouldnt seem slow.a pair of clustered vax780s never seemed to break a sweat.
maybe it's just perspective, maybe it's the client/server design,maybe it's what we did with it.
vms was elegant. thats something NT never had.

> Date: Fri, 20 Apr 2012 15:47:29 -0700
> From: oboguev at yahoo.com
> To: simh at trailing-edge.com
> Subject: Re: [Simh] Alpha simulator performance
> 
> > While we're in "wish list" mode, I'd like to see SimH emulate Alpha or Itanium, 
> >
> >so I could use it to run  newer versions of OpenVMS than 7.3. There are free 
> >versions of commercial Alpha emulators available, but they only run on Windows 
> >(BLEAH) and their performance is intentionally limited, presumably to get people 
> >
> >to buy the full version.
> 
> If you are concerned about performance, it is unlikely that SIMH implementation 
> of Alpha (which apparently is in works, but hard to guess when it might become 
> available) will "ever" match the performance of free versions of commercial 
> emulators. The latter do JIT binary compilation, whereas SIMH performs 
> interpretation of instruction stream and is unlikely to have JIT for the 
> foreseeable 
> 
> future if ever at all.
> 
> FreeAXP performance may be throttled down compared to full Avanti, but it is 
> still very fast -- much, much faster than SIMH VAX alongside it.
> 
> Also note that FreeAXP is about 3x faster when running on 64-bit version of 
> Windows compared to being executed on 32-bit Windows (just as can be expected 
> for the emulation of 64-bit processor).
> 
> To give a rough idea, here were the results CHARON/SRI benchmark executed on
> FreeAXP running on i7 2600, 3.40 GHz on 64-bit Windows:
> 
>     Test started [...] for a AlphaServer 400 4/166 CPU with VMS V8.3
> 
>     Sequential test results:
> 
>               Whetstones   Dhrystones   VUPs
>     Run 0          81.7        203735      144.5
>     Run 1          80.3        200222      144.5
>     Run 2          79.0        203735      144.0
>     Run 3          80.3        200222      145.0
>     ---------------------------------------------
>     Average        80.3       201978      144.5
> 
>     Interleaved test results:
> 
>               Whetstones   Dhrystones   VUPs
>     Run 0          81.7        200222      145.0
>     Run 1          80.3        203735      145.0
>     Run 2          80.3        203735      144.5
>     Run 3          81.7        200222      144.5
>     ---------------------------------------------
>     Average        81.0       201978      144.8
> 
> By the way of comparison, same test executed in native Windows x64 mode on the 
> same machine (with SSE code generation disabled during compilation) produced 
> only 150 000 Dhrystones ;-), albeit was 150 times faster than virtual Alpha on 
> Whetstones.
> 
> As a side note, I personally was never quite able to understand the reasoning of 
> 
> people who extoll VMS and simultaneously "bleah" about "Windoze", which after 
> all at its foundations is to a significant extent a clean and neat 
> reimplementation of 
> 
> VMS/Mica architecture at a new technological volution.
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