386SX Drop in Board

[Mr. Jim's Own Logon]

In article <96 at opus.ATT.COM>, cab at opus.ATT.COM (C. Anthony) writes:
> I posted a message about 3 weeks ago asking for leads on
> 386SX Drop in boards, to replace thet '286 processor in an AT.
> 
> So far the only manufacturer I've heard of working on such a product
> is Cumulus Corp.  I don't have their address or number, (and can't
> find the PC magazine containing it.  If some kind soul will send it to
> me, I'll follow up.
> 
    There are basically three problems with designing and then selling 
such a product. The first: limitations to what it can do. Because of the
floating point changes on the 386SX it is completely incompatible with 
the 80287 (although at one time Intel did try to come up with a circuit 
that would allow the two to work together). And the cost of the 387SX is
high enough to avoid adding it in for all cases.

   The second: varying timing requirements for PC compatibles. Since there
never was a specification for any timing on the original IBM PC, and since
not all vendors actually meet all the published timings for the 286 in their
designs (probably less than 1/3 actually meet all worst case timings), the
386SX design is extremely difficult to make work in more than half of the 
PCs on the market. RAM timing problems mostly, but interrupts, DMA, and
(the most varying) the bus slot timing. Making it work for just a few of the
machines out there is a difficult thing to justify, and even more difficult
to support.

   The third: customer support. The magnitude of problems that you will 
encounter is astronomical. One portion of the calls will be from people
that can't get the board to work in their BigBomb AT compatible, and they
want $200 worth of support time for a board that cost $150. A bigger 
problem is someone who buys the 386SX card and then installs 32 bit UNIX
on it. And it doesn't work just quite right. The UNIX vendor will instantly
pass the blame to the 386SX adaptor. You now have to try and support all of
the code that this guy is going to run on his new processor. You also have 
to answer the problems of "this DOS program used to run, and now it gets
errors when I run it on the 386SX, why is that?".

   Anyway, there are more problems if you really want to know about them:
mechanical constraints to the adaptor, PGA vs. PLCC 286s, power requirements,
noise from the 286 machine, FCC issues. Not simple problems. Several 
companies which announced products have already pulled them back. You may
never see them on the open market. Being sold to large companies trying to
upgrade several hundred identical 286 machines, well, thats a different story.

						-Jim Wall
						 Bell Technologies, Inc.