Path: utzoo!dciem!nrcaer!xios!greg
From: greg@xios.XIOS.UUCP (Greg Franks)
Newsgroups: comp.unix.wizards
Subject: Re: UNIX performance on a VAX & 68020
Message-ID: <527@xios.XIOS.UUCP>
Date: 31 May 88 12:43:49 GMT
Article-I.D.: xios.527
Posted: Tue May 31 08:43:49 1988
References: <1273@ark.cs.vu.nl>
Reply-To: greg@sdn.UUCP (Greg Franks)
Organization: XIOS Systems Corporation, Ottawa, Ontario, Canada
Lines: 21

In article <1273@ark.cs.vu.nl> polder@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).




-- 
Greg Franks                   XIOS Systems Corporation, 1600 Carling Avenue,
utzoo!dciem!nrcaer!xios!greg  Ottawa, Ontario, Canada, K1Z 8R8. (613) 725-5411.
       "Those who stand in the middle of the road get
               hit by trucks coming from both directions." Evelyn C. Leeper.