From owner-freebsd-questions Thu Dec 14 15:03:18 1995 Return-Path: owner-questions Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id PAA25568 for questions-outgoing; Thu, 14 Dec 1995 15:03:18 -0800 (PST) Received: from beach.silcom.com (root@beach.silcom.com [199.201.128.1]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id PAA25557 for ; Thu, 14 Dec 1995 15:03:16 -0800 (PST) Received: by beach.silcom.com (8.6.12/SMI-4.1) id OAA01214; Thu, 14 Dec 1995 14:26:27 -0800 Received: (from alan@localhost) by trickler.uu.silcom.com (8.6.9/8.6.6) id OAA01240; Thu, 14 Dec 1995 14:07:49 -0800 Date: Thu, 14 Dec 1995 14:07:49 -0800 From: "Alan D. Trombla" Message-Id: <199512142207.OAA01240@trickler.uu.silcom.com> Subject: Re: Upgrade - CPU, clock? To: wes@intele.net Cc: questions@freebsd.org Sender: owner-questions@freebsd.org Precedence: bulk >From: Barnacle Wes ... >> >> Questions: >> 1. What is the fastest chip I can plop into my ZIF socket with no other >> changes? > >A DX4/120, depending on how configurable the motherboard is. Do you have >the documentation for the motherboard? If so, check the cpu speed jumpers >and see what settings it will allow. Am I correct in assuming that a DX4/120 has (external) bus speed of 33MHz? My manual (probably written pre-DX4) has 3 sets of jumper settings for: 1. 486DX/DX2 2. 486SX 3. 487SX/Overdrive Although there is no listing for DX4 CPUs, wouldn't a DX4/120 be (from the motherboards point of view) the same as a DX2/66 ? >Beware that FreeBSD has problems with *some* Cyrix and AMC cpus. Can anyone give me a list? >> 2. Can I just change the crystal to get a 50MHz system? If so, will >> my ATI GUP handle the faster bus? (There are no other VLB boards.) >> Is my memory (assuming it *is* 70ns) fast enough? > >Sure. It'll probably result in a dead system, but you can do that. >I know several people who immediately upon recieving DX/2-66s at work >changed the clock to 40Mhz. Result: system locked up after 5-6 minutes. >A cpu fan on the 486 extended this to 15-20 minutes before locking up. I mean, of course, change the crystal *and* put in a 50MHz CPU >Also, the VL-Bus is very critical about timing; setting the bus speed >above 33 Mhz may make your periperhals stop working. If your mother >board has switches for VL-Bus at system clocks above 33 Mhz, it'll >probably just divide the system clock by two, resulting in a 20 or 25 >Mhz VL-Bus. Depending on your video and disk I/O, this may actually >slow the system. The motherboard supports 486DX50 (manual: "To change the CPU speed you must change the oscillator", meaning cahnge the crystal?). So it should support a 486DX2/100 (at 50Hz)? Is there such a thing? Thanks for your help, Alan Alan D. Trombla--------------------------------------alan@iplab.ece.ucsb.edu