[Info-vax] Floating point emulation of OpenVMS / Alpha / ES

[abrsvc]

On Tuesday, October 11, 2022 at 4:26:40 PM UTC-4, Arne Vajhøj wrote:
> On 10/11/2022 4:20 PM, Nick K wrote: 
> > I'm curious what to expect when moving OpenVMS from an Alpha / ES 
> > server to a virtual machine with an emulator. I'm mostly looking at 
> > the single threaded / single core floating point performance. Are 
> > there emulators that are significantly better / worse for this task? 
> > Can I expect a comparable running time on the fastest (clock speed) 
> > Intel Xeon money can buy today?
> I don't have an answer. 
> 
> But two important questions must be: 
> 1) does the Alpha emulator do JIT? 
> 2) are you using F/G or S/T floats? 
> 
> JIT and S/T could potentially be pretty fast. 
> 
> Arne

I will state that little can be gained from looking at the standard benchmarks unless you know the relationship of them to your own application.  I have not found single threaded performance numbers to relate to overall application performance either.  That being said, I am aware of many installation using the Charon emulators that perform at or exceed "real" hardware levels.  A lot depends upon the application.  Some emulators perform JIT, others prescan the code stream and generate the instructions in parallel to their execution.  Your mileage may vary.

For full disclosure, I work for the company that created and supports the Charon product stream. I can not comment on the performance of other emulators.

Dan