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View Full Version : 80287 Math Co-processor Upgrade on a 1984 IBM AT 5170



Super-Slasher
June 28th, 2003, 11:51 PM
I am curious to know if anyone here has ever had any experience with this procedure as I have found a few sources for actual Intel legacy processor and co-processor chips, and am curious as to how a math co-processor would improve performance. Can anyone tell me what sort of performance improvements I would be expecting?

What about installation? Is it just a type of "plug and play" procedure; just press it into the co-processor slot and you're done? Or is it more complex/in-depth than I am hoping? hehe

Also, there are actually four different types of 80287 math co-processors to choose from - which one is the type I need for my perticular system and what are the differances between them? Could the same co-processor be used in the different types of AT (6MHz and 8MHz, that is)?

80287-3 80287-6 80287-8 80287-10I'm strongly considering doing this upgrade for the experience and to see first hand what a typical computer upgrade from when I was born would be like, performance wise, anyways. Plus you just don't see alot of legacy computers with the optional co-processor installed anyways... would make my machine a bit more unqiue, which I truly appreciate when it comes to vintage and antique items.

Thomas Hillebrandt
June 29th, 2003, 12:04 AM
Well...I can't actually give you any good advice on the installment of a co-processor in the AT...I've never done such a thing myself. I did get an old IBM PC - from the PS/2 line, I think - that had one installed, but other than that...

At any rate, my vote is cast primarily on one distinct point of view I have about these old machines. Upgrading them is fine, as long as it's done with legitimate stuff.

What I mean is; installing a co-processor, harddrive, extra memory, sound card, SCSI-adapter or whatever in an old AT or XT or whatnot - is fine. That would be done back then anyway, so why not? However, upgrading, say a Commodore 64 with a super 100 mhz processor, 2 MB of RAM and what-ever else some new processor-expansion I saw for a C64 a year ago offered, is not okay. That would have NEVER been done while the C64 had its day. The technology wasn't available! So that - in my book - is a no-no...

Even worse, of course, is sawing in the cases and soldering stuff onto the PCB...

Am I rambling now??? :lol:

CP/M User
June 29th, 2003, 01:52 AM
"Super-Slasher" wrote in message:

> I am curious to know if anyone here has ever
> had any experience with this procedure as I
> have found a few sources for actual Intel
> legacy processor and co-processor chips, and
> am curious as to how a math co-processor
> would improve performance. Can anyone tell
> me what sort of performance improvements I
> would be expecting?

My 386 laptop has a maths co-processor in it,
however I haven't really taken a look, I've
only opened it up to put some memory in.
Only reason I know it's there is it's comming
up in the BIOS setup program. It's hard to
say if it does improve anything. Maybe if I
setup PC-DOS to detect it (if that's possible),
it may go. Most of the programs I've seen
tend to consentrate on the main CPU though.

I don't know if putting one in a 286 would
increase it all that much, if it were a
8086/8088 based computer & you wanted
to put a 8087, then there would be some
programs which would use it (Turbo Pascal
is one). A 286 though includes the
instructions from the 8087 so they are
there (plus some of it's own). I'd check
the Operating System to see if in some
way can use the maths co-processor to
improve the performance. For example,
if I recall correctly, it was possible to
include all maths processing to it which
would free up the 286 CPU itself (though
I'm not sure about this!).

> What about installation? Is it just a type of
> "plug and play" procedure; just press it into the
> co-processor slot and you're done? Or is it more
> complex/in-depth than I am hoping? hehe

Personally I haven't had any experience in
installing a maths co-processor, but I've seen
the slot for it in my 386s & it looks like the sort
of connection which is designed to go in only
one way (there is one pin which is designed to
line up with the pin on the maths co-processor).

> Also, there are actually four different types of
> 80287 math co-processors to choose from -
> which one is the type I need for my perticular
> system and what are the differances between
> them? Could the same co-processor be used
> in the different types of AT (6MHz and 8MHz,
> that is)?

This is where it gets tricky because I've asked
this question & got all sorts of answers.
Originally I read that you had to match the
speed of the CPU with the speed of the maths
co-processor, but others have told me that in
the case of a 386 you can insert a 40Mhz
maths co-processor into a machine running
at 33mhz or 25mhz! This maybe different for
a 286 as I found out the hard way with these
computers the hardware might be the same
but certain restrictions apply to what you can
do! :-( One person told me that I could have
even put a 486 maths co-processor into a
really fast 386! (might be a question of
mainboard & if it can support a 486
processor).

Due to all the confusion, I just decided to call
it in. However if I had to get a 287 processor
for my non-existant 286, then I'd stick with
the same speed. I hear it's risky putting a
slower co-processor into a computer with a
faster CPU. If you know that you could get
your money back in case you got a faster
co-processor, knowning that it could possibly
work on it, then yes I'd perhaps get a faster
one, that is if you cannot get one the same
speed! :-)

> * 80287-3
> * 80287-6
> * 80287-8
> * 80287-10

> I'm strongly considering doing this upgrade
> for the experience and to see first hand
> what a typical computer upgrade from when
> I was born would be like, performance wise,
> anyways. Plus you just don't see alot of
> legacy computers with the optional
> co-processor installed anyways... would
> make my machine a bit more unqiue, which
> I truly appreciate when it comes to vintage
> and antique items.

Cheers.

Erik
June 29th, 2003, 07:20 AM
Installing a 287 is easy. Just make sure it's oriented properly and press it into the socket.

You're not really going to notice it much, though. It's only going to make mathamatical calculations faster and only on software that supports the chip. Most programs just ignore it.

Good luck!

Erik