Date: Mon, 24 Feb 1997 23:35:46 +0100 (MEZ) From: "Hr.Ladavac" <lada@ws2301.gud.siemens.co.at> To: bdodson@beowulf.utmb.edu (M. L. Dodson) Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Adding memory slows down 486 to less than 386SX! Message-ID: <199702242235.AA204803746@ws2301.gud.siemens.co.at> In-Reply-To: <199702242128.PAA08444@beowulf.utmb.EDU> from "M. L. Dodson" at Feb 24, 97 03:28:01 pm
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E-mail message from M. L. Dodson contained: > > Hello, > > I just upgraded a 486DX-25 from 8MB to 20MB memory and sequential > character disk I/O to a SCSI disk is now slower than to an IDE disk > on a 386SX! > > The machine "feels" slow, also. Not only under FreeBSD, but also under > Win95 (for processes that do not cause swapping). I have included bonnie > results below. The 486 has a VLB BusLogic 445C bus mastering SCSI > controller, the 386SX a normal IDE builtin. Note that the 486 is 4-5X > faster for block I/O, which is what I was expecting for everything. The > kernels do not have bounce buffers enabled. Both machines were lightly > loaded. The 486 is a NFS server, the 386SX is a NFS client (it will > eventually be a router for my home network, but ppp was not running > during these benchmarks). Nothing was NFS mounted. > > The BIOS setup for the 486 is standard as far as I can tell: 2-1-1-1 > memory timing, 256KB cache was enabled, no cache waitstates. The 386 > was box stock, also, as far as I know. I have no documentation on > the 386 builtin controller, but BSD probes it as a standard IDE > controller. > > I don't get any memory fault indications. > > Note that the 386SX is only running a 10MB bonnie file, whereas the 486 > was running a 30MB. But I am talking sequential input/output, per > character, rates: 82K/sec vs 55K/sec output and 87K/sec vs 64K/sec for > input. > > And why is CPU utilization so high for the block I/O on the 486 > relative to the 386SX? > > Any help would be appreciated. I'm at a loss. > > Bud Dodson How much Level-2 cache do you have on the '486 board? Some boards could only cache the lower 16MB unless you had more than 128K cache. Mine was one of these :( /Marino
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