Date: Thu, 14 Dec 1995 14:07:49 -0800 From: "Alan D. Trombla" <alan@trickler.uu.silcom.com> To: wes@intele.net Cc: questions@freebsd.org Subject: Re: Upgrade - CPU, clock? Message-ID: <199512142207.OAA01240@trickler.uu.silcom.com>
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>From: Barnacle Wes <wes@intele.net>
...
>>
>> 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
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