Twospruces
Veteran Member
Hi all,
I recently acquired and revived an old 286 laptop from Sharp. Quite a nice compact machine actually.
I thought I would try to add then 80C287.
I purchased a part off ebay : IIT 2C87 math coprocessor.
Didn't work out; maybe it was a fake? Hard to know.
What I observed:
* the installation is simply plug it in - nothing else to do apparently
* when installed, the laptop boots and runs, however
-- Checkit3 detects the 287
-- but it has trouble with any benchmarks. It fails to detect clock frequency. It shows incorrect values on the axes.
-- It fails to run the CPU or math co-pro benchmarks - meaning that the test completes and reports "00" for Dhrystones and Whetstones
-- checkit3 also seems to be unable to make calculations - which to me tells me the math is now "broken"
* PC-matlab now runs but it also can't compute any math.
I looked at the hardware signals and nothing seems off.
* the BUSY line on the 287 is toggling
* PREAQ and PEACK are toggling away
* all the signals appear to be correctly connected
Any thoughts? Did I get a bad chip?
It does appear that the CPU is requesting a calculation, because the system believes there is a 287.
The BUSY signal from the 287 goes to an LSI chip, which is then responsible to generate BUSY to the CPU.
Should I see BUSY toggling at the CPU as well? I would think so.. I assume that when the 287 is computing the 286 needs to wait.
Interestingly, BUSY input to the 286 processor is high through all the 287 activity caused by Checkit3.
I bet that's it.
Anyhow, comments?
thx
I recently acquired and revived an old 286 laptop from Sharp. Quite a nice compact machine actually.
I thought I would try to add then 80C287.
I purchased a part off ebay : IIT 2C87 math coprocessor.
IIT 2C87-10 Math Coprocessor 287 FPU 10MHz 80C287 Ceramic DIP40 Processor 80287 | eBay
Find many great new & used options and get the best deals for IIT 2C87-10 Math Coprocessor 287 FPU 10MHz 80C287 Ceramic DIP40 Processor 80287 at the best online prices at eBay! Free shipping for many products!
www.ebay.ca
Didn't work out; maybe it was a fake? Hard to know.
What I observed:
* the installation is simply plug it in - nothing else to do apparently
* when installed, the laptop boots and runs, however
-- Checkit3 detects the 287
-- but it has trouble with any benchmarks. It fails to detect clock frequency. It shows incorrect values on the axes.
-- It fails to run the CPU or math co-pro benchmarks - meaning that the test completes and reports "00" for Dhrystones and Whetstones
-- checkit3 also seems to be unable to make calculations - which to me tells me the math is now "broken"
* PC-matlab now runs but it also can't compute any math.
I looked at the hardware signals and nothing seems off.
* the BUSY line on the 287 is toggling
* PREAQ and PEACK are toggling away
* all the signals appear to be correctly connected
Any thoughts? Did I get a bad chip?
It does appear that the CPU is requesting a calculation, because the system believes there is a 287.
The BUSY signal from the 287 goes to an LSI chip, which is then responsible to generate BUSY to the CPU.
Should I see BUSY toggling at the CPU as well? I would think so.. I assume that when the 287 is computing the 286 needs to wait.
Interestingly, BUSY input to the 286 processor is high through all the 287 activity caused by Checkit3.
I bet that's it.
Anyhow, comments?
thx