Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!sdrc!thor!scjones
From: scjones@thor.UUCP (Larry Jones)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: coprocessor... how fast???
Message-ID: <142@thor.UUCP>
Date: 28 Jan 91 19:01:42 GMT
References: <1991Jan27.172506.15133@ncsuvx.ncsu.edu>
Organization: SDRC, Cincinnati
Lines: 19

In article <1991Jan27.172506.15133@ncsuvx.ncsu.edu>, big@hobbes.catt.ncsu.edu (Alan Porter) writes:
> Forgive me, but I am still new at this game.
> How fast must a math coprocessor be to work and to be
> effective?

It must be rated for at least the clock speed that your motherboard
supplies.  In most cases, the external clock supplied to the 287 is
the same as the external clock supplied to the 286 -- the 286 divides
the external clock by 2 to get the internal clock (which is what the
rating refers to) but the 287 divides the external clock by 3, so the
287 would need to be at least 2/3 the speed of the 286.  Thus, a
12MHz 286 would need an 8Mhz 287 and a 16Mhz 286 would need a 12Mhz
287.  Although this scheme is common, it is by no means universal, so
you should really make an effort to find out the details for your
particular motherboard.
----
Larry Jones, SDRC, 2000 Eastman Dr., Milford, OH  45150-2789  513-576-2070
Domain: scjones@thor.UUCP  Path: uunet!sdrc!thor!scjones
Start tying the sheets together.  We'll go out the window. -- Calvin