Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!wa3wbu!john
From: john@wa3wbu.UUCP (John Gayman)
Newsgroups: comp.sys.ibm.pc
Subject: Re: 8087 Coprocessor
Summary: 8087 XT
Message-ID: <657@wa3wbu.UUCP>
Date: 13 Jul 90 23:12:44 GMT
References: <169@evtprp0b.UUCP>
Organization: @ WA3WBU, Marysville, PA
Lines: 36

In article <169@evtprp0b.UUCP>, tea6219@evtprp0b (Terry E. Acker) writes:
> 
> I have an XT with a V20 processor running at 8/4.77Mtz.  What speed
> coprocessor do I need.  If there are different speed 8087s, can I
> use a 4.77Mtz 8087 and set the system speed to 4.77?  What if I run
> the system at 8Mtz with a 4.77Mtz 8087?  Will it work?  Will it
> overheat?
> 

   Unlike the 286 machines, your coprocessor runs at the same clock speed
as your 8088 or it your case V20. So if buying a 8087 you want to get
one designed for the highest clock rate you'll be running.... 8 Mhz.
You *could* if you so desired, purchase a 4.77 Mhz chip and run your
machine at the slower clock rate.

   I ran into an interesting situation regarding 8087's. When I bought
my first XT-class machine way back when it was to be a standard 4.77 Mhz
unit. I had applications which insisted on a coprocessor. So I ordered
ahead of time a 4.77 Mhz 8087. When my machine arrived, low and behold there
was a note telling me they were shipping "turbo" machines (8 Mhz) at no
extra charge. I could not return the 8087 for a faster one so I put it in
anyway. I ran that machine that way for about 3 years. I can't really
advise you to intentionally buy a slower chip and run it at the faster
speed but if you alread have a chip I would certainly try it. In my case
had I known I would be getting a 8 Mhz unit, I would have purchased a 
8 Mhz 8087.


						John



-- 
John Gayman, WA3WBU              |           UUCP: uunet!wa3wbu!john
1869 Valley Rd.                  |           ARPA: john@wa3wbu.uu.net 
Marysville, PA 17053             |           Packet: WA3WBU @ WB3EAH