Hi,
I found this 80387-20 SX105 coprocessor and hoped to install it on a Soyo sy-019i Eteq 82C491 mobo. It support only 33 and 40Mhz cpu but I thought that the coprocessor could works at lower speeds. Was I wrong? Cause the system hang after ram post "waiting" when installed.
Thank
Maybe it's cause I have the DX-40 version of cpu and this could be an SX 387?
This is a 387SX Package:
This IT FPU runs fine at 33Mhz 😀
Yours is a DX Variant, i think.
SX105 is SSPEC. Not Variant.
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Where did you install sx coprocessor? It won't fit on dx board.
Requests are also possible... /msg kixs
Looks like he try's to overclock an Intel 20Mhz FPU on a DX40 386.
But the Intel Parts don't like overclocking
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Here I am, the co cpu is an Intel (without logo) ceramic A80387-20 SX105 on pin socket (like the Am386DX-40) the board above has a cocpu socket larger that the 387 but seems to fit at the center anyway. I don't know if it's running at 40Mhz cause it would obviously not start I imagine but I hoped frequency would different from the main cpu.
FPU and CPU have to run synchronous clock.
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My best guess is that the system locks up because you try to run the 20 MHz FPU at 40 MHz.
Carefully remove the FPU and try if it comes up again.
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wrote:My best guess is that the system locks up because you try to run the 20 MHz FPU at 40 MHz.
Carefully remove the FPU and try if it comes up again.
Yes, after removing the FPU it booted ok. I will probably need to find a 40Mhz version. ULSI are good?
It's good to hear yours worked again after you removed the FPU... unfortunately for me, the board still hang's at "waiting". 🙁
wrote:wrote:My best guess is that the system locks up because you try to run the 20 MHz FPU at 40 MHz.
Carefully remove the FPU and try if it comes up again.Yes, after removing the FPU it booted ok. I will probably need to find a 40Mhz version. ULSI are good?
Depends: ftp://retronn.de/docs/FPU/coproc.txt
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wrote:It's good to hear yours worked again after you removed the FPU... unfortunately for me, the board still hang's at "waiting". 🙁
Sorry 🙁
If I read that before I wouldn't even try mine co cpu. With my mainboard I already had so many problems (broken traces) before building it...
wrote:FPU and CPU have to run synchronous clock.
Intel (and only intel) FPUs support asynchronous clocks, but the motherboard needs to support it. There is usually a spot for an extra oscillator that determines the FPU speed.
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wrote:wrote:FPU and CPU have to run synchronous clock.
Intel (and only intel) FPUs support asynchronous clocks, but the motherboard needs to support it. There is usually a spot for an extra oscillator that determines the FPU speed.
True story...
