Math coprocessors

From: Jack Peacock <>
Date: Mon Apr 6 13:40:25 1998

Ward Donald Griffiths III wrote:
> Max Eskin wrote:
> >
> > I found a PS/2 Model 70 recently, which would normally have a 386,
> > but the previous owner installed a Cyrix 486 upgrade chip. Does
> > anyone know if I can use a 386 math coprocessor with this? I want
> > to run AutoCAD.
> The i486 has a coprocessor built in, I assume that the Cyrix does
> as well. Try the software. IIRC, AutoCAD doesn't _require_ a math
> coprocessor, but one does help performance by an order or two of
> magnitude on a 386.
> --
No, the Cyrix 486DL (I assume it is a DL or DR2 if it's in a 386
motherboard) is not the same as an Intel 486. The Cyrix 486DL was an
upgrade CPU for the 386 pinout, adding a 486 instruction set and 1K
internal cache. The 486DR2 version was clock doubled. These CPUs do
not have floating point. Generally an Intel 80387 did not work
reliably, but the Cyrix 487 co-processor did. ULSI (and I think IIT)
also made 487s. You can try the Intel 387, sometimes they ran ok,
mostly it depended on the speed range used.
        Jack Peacock
Received on Mon Apr 06 1998 - 13:40:25 BST

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