lane@cs.dal.ca (John Wright/Dr. Pat Lane) (03/06/90)
I had hear that 80*87 chips tend to run hot but I didn't realize how hot
until I installed one in my 286 clone. It nearly burnt my finger to
touch it. Concerned, I called Intel's tech support line (1-800-538-3373
if you're interested - one of the better one's I've tried) and the fellow
I talked to said "yep, you can fry eggs on them...if you can hold you finger
on one for more than 2 seconds either the chip is dead or the nerves in your
finger are". He went on to say that the chip is carefully designed with a
ceramic case so as to withstand this heat and last at least the 5 years for
which the thing is warranteed.
I asked him about putting a heat sink on the chip and he recommended
against it, especially gluing one on with epoxy, since this might disrupt
the chips own heat dissapation ability and make things worse.
Now this might be a conservative, "if-it-isn't-in-the-book-don't-do-it"
response. What do the engineering-types here on the net think? Anyone
have any experience in this area?
BTW, one area of confusion with co-processors is getting the right speed.
What I've always heard is that with *most* 8086, 8088, and 80386 mother-
boards you use the same speed co-processor as the maximum speed of the CPU.
Most (but not all) '286 boards run the co-processor at 2/3 the CPU speed.
One is supposed to check with the manufacturer to find out for sure which
co-processor to use. I have no idea who the manufacturer of mine is - it's
a clone and there's no name on the motherboard!
Mine is a 6/10MHz switchable '286 so assuming the 2/3 rule, my co-processor
should run at 4 or 6.67 MHz. It's an 80287-8 so I should be OK. To check
the 2/3 assumption, I ran a pgm from the PC Tech Journal called ATPERF (I
got it from SIMTEL) which tests things like apparent CPU and co-processor
clock rates, wait states, refresh overhead, etc. by doing a series of timing
tests (the co-processor rate is determined by timing a floating point divide).
Running it with the co-processor installed, I got the co-processor speeds
I was expecting so I guess I'm OK there...
--
John Wright ////////////////// Phone: 902-424-3805 or 902-424-6527
Post: c/o Dr Pat Lane, Biology Dept, Dalhousie U, Halifax N.S., CANADA B3H-4H8
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