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From: dhinds@portia.Stanford.EDU (David Hinds)
Newsgroups: comp.sys.ibm.pc
Subject: Replacing an 80386 with an 80486
Message-ID: <9589@portia.Stanford.EDU>
Date: 27 Feb 90 05:23:21 GMT
References: <29108@amdcad.AMD.COM> <1640057@hpspcoi.HP.COM> <25E98AD7.9457@maccs.dcss.mcmaster.ca>
Sender: David Hinds <dhinds@portia.stanford.edu>
Organization: Stanford University
Lines: 22

In article <25E98AD7.9457@maccs.dcss.mcmaster.ca>, cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn) writes:
> $For example the numeric coprocessor and a memory cache are include in the
> $chip. As for upgrading, that depends on whether your 386 was designed
> $for upgrading. There is a major difference in the motherboard design
> [...]
> 
>    Yup ... the whole motherboard has to be replaced unless it was
> designed for upgrading, and very few machines are designed for upgrading.
> -- 
    It seems like it would not be all that hard to design a teeny daughter
board that fits into the 80386 socket, and carries an 80486.  Is there a
real difference in design of the support circuitry, that an 80486 wouldn't
work in place of an 80386?  From what I understand about the '486, to the
outside world (i.e., the motherboard), it shouldn't look much different from
an 80386.  I would guess that the 80486 might have a couple extra control
lines that might need to be tied off somehow, but it should be able to start
up off of a standard 80386 BIOS, even.  When '486 prices fall, this seems
like a potentially inexpensive upgrade - instead of getting a fast 80387,
for example.

 - David Hinds
   dhinds@portia.stanford.edu