[Info-vax] Unix on A DEC Vax?

[John Wallace]

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?