[Info-vax] Unix on A DEC Vax?

[Rich Jordan]

On Jan 17, 2:18 am, John Wallace <johnwalla... at yahoo.co.uk> wrote:
> On Jan 17, 1:38 am, Stephen Hoffman <seaoh... at hoffmanlabs.invalid>
> wrote:
>
> > On 2013-01-16 23:13:14 +0000, ChrisQ said:
>
> > > With any vax though, don't expect 3Ghz Xeon performance :-)...
>
> > Or with a 3 GHz Xeon and a software emulator, expect to get VAX
> > performance.  :-)
>
> > --
> > Pure Personal Opinion | HoffmanLabs LLC
>
> What kind of performance is reasonable to expect from emulated
> systems? I know that's a "how long is your piece of string" question,
> but is it answered anywhere,objectively or anecdotally?
>
> Someone I know earlier this week did a quick (and therefore not
> necessarily entirely valid) test of an existing mostly-computebound
> single-threaded workload on a well known commercial Alpha (not VAX)
> emulator. The workload was the only load on the emulator allegedly on
> a dedicated modern x86 server.
>
> The same workload was measured in its current natural environment, an
> AlphaServer 2100 5/250 (mid 1990s?) which was also supporting its
> usual interactive and batch workload (at the time of the tests a
> relatively light workload).
>
> The test workload on the emulator was three times slower (ie runtime
> three times longer), which was a bit of a surprise.
>
> Is that kind of performance degradation (vs the same workload on
> antique native hardware) to be expected? Does performance vary widely
> with different emulators? Does the host environment (e.g. VMware vs
> native) matter much?

I remember reading (sorry, no reference) that the 1990s-early 2000s
VAX emulators would run at roughly 1 VUP per 100MHz of processor speed
on wintel hardware.  I don't know if that is still relevant with all
the non-clock-tracking performance improvements that have been made.