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.