VOGONS


First post, by waterbeesje

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In my collection I have a few XT class computers running the 8088 or 8086 processor. All without 8087... for now.

3 times IBM model 30; 8086 at 8MHz
Multitech MPF-PC; 8088 at 4.77MHz
Philips P3105; V20 at 8MHz
Philips P3120; 8088 at 10MHz
Tulip PC Compact 2; 8088 at 10MHz
a working Turbo XT board without destiny; V20 at 8MHz

Now I'm looking to get myself some coprocessors for these systems and may get myself a lot of 5 to 10 pcs 8087-2 chips.
Not really a reason to do this, but hey... Wouldn't you? 😁

Now these are rated for 8MHz of course but I'm wondering: how well would or wouldn't they do in the two 10MHz computers?

Getting an overclock of 25% may seem madness to some, but I ran a 8088-2 at 10MHz for a few years in my PC Compact 2 befor I realized it was actually overclocked (and eventually replaced with a V20 as it originally came with off factory)

Stuck at 10MHz...

Reply 1 of 2, by Anonymous Coward

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If the 8087 has a later date code it will probably overclock. Just be aware that all 8087s were based on 3 micron NMOS designs. Because of the way the 8087 is interfaced to the 8086/8, if your FPU overheats it will crash the CPU too. 8087 is probably one of the worst chips you can overclock. I don't recommend it. 8087-1 is not that hard to find.

I once had some problems with a C8087-1 chip I got for my 10MHz V30. I'm not sure if the FPU was remarked or defective, but it wasn't stable at 10MHz and constantly caused my system to lock up. They actually don't really idle, because they constantly decode CPU instructions waiting for an ESC (escape to co-pro) function to come along. So they generate heat pretty much all the time, and they are really damn HOT!

"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium

Reply 2 of 2, by waterbeesje

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The photos were not too clear, but it looked like they are all dated 1984, so it'll probably would work I guess.

To prevent overheating I could install a little heat sink in top and hope the case just ventilates enough to help keeping temperatures below critical. At least for the 8MHz computers. For the 10MHz ones I'll go and look for some 8087-1 stuff 😀

Stuck at 10MHz...