UNIX performance on a VAX & 68020

[Greg Franks]

In article <1273 at ark.cs.vu.nl> polder at cs.vu.nl (Paul Polderman) writes:
>Benchmarks show that a 68020 is at least as fast as a VAX-11.
>But if I start e.g. 6 C-compilers on a UNIX-system running on a 68020,
>the performance collapses completely (even when no swapping is necessary),
>where on a VAX the system-performance stays reasonable.
>I wonder why this is so, when the CPU-speeds are roughly the same.
>

I'll bet that the I/O system has a higher throughput and is a lot faster
on a VAX than on your 68020 system.  Another possibility is context
switching: the VAX may be able to support a higher number of runnable
processes (eg, doesn't have to reload page tables as often etc).




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