lane@cs.dal.ca (John Wright/Dr. Pat Lane) (04/13/89)
Hello. I've been confused about this for a while.
What are the rules for installing a math co-processor regarding the clock
speed of the system. Must the 8087/80287 be the same speed as the CPU?
Can it be slower?/faster? If the CPU is switchable is it safe to install
a co-processor that is only rated for the slower speed and only run at the
slow speed when doing floating point operations (sounds dicey to me!)?
I have an Intel D80287-8 (L6300169) that I tried putting in a 6/10MHz
80286 clone. It worked fine at 6MHz but I was scared to try 10MHz.
I'm also a bit confused about the speed of this system and whether it
is using any wait states. The motherboard is a Zehntel/ICT, if that
means anything to anybody. I can't read the CPU because there's a heat
sink glued on it. As near as I can tell, it is jumpered for no wait
states but it's hard to tell as the jumper isn't described in the little
booklet. It does say the low speed is 6MHz and the high speed is either
8 or 10 MHz; I guessed this would depend on the wait state setting, no?
Or does it depend on the crystal oscillator?
Is there a way to test for wait-states using software or some-such?
Norton's SI gives me 10.3 and PC Mag's Benchmark pgms give me 1.3 relative
to an 8.00MHz AT. Interestingly, BENCH20 which tests memory access times
gives me 1.3 (*8MHz) on "conventional" (0-640K, I assume) read/write and
1.0 on "extended" (384K extended RAM) read/write.
What really gets me though is that the memory (1 Meg) is only 150 nsec
(NEC D41256C-15's). Should it not be at least 120 nsec for 10MHz?
I tech engineer mentioned to me once that besides CPU speed and wait-states
there was the question of bus speed and that some machines have a fast CPU
but a slow bus. Anybody know anything about that? Again, is there a way
to measure this using software?
Most grateful, as always, for any enlightenment. Reply by mail for best
results. Thanks.
--
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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