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980625 - 5560-W2B Modified BIOS and Overclocking
I am totally blind about hex code, assembler, programing and such matters. I
really admire those people who can read or write computer language. Here is one
such a guy and his name is Mr. S. He joined the Room #4 in 1997 (almost same
time when I joined the Room) with his
5560-W0/W1. 5560-W looks like PS/2 8590
but the planar and complex are a bit different from that of 8590. He tried to
overclock these machines. 5560-W0 can take OSCs rated between 30MHz to 32MHz
without 102 error but the complex is a older type like PS/2 Type-1 25MHz. The
complex used in 5560-W1 is derived from PS/2 Type-2 H and is faster than W0
complex but it can not accept any OSCs rated higher than 54MHz (27MHz system
clock). Once a higher rated OSC installed 61-W1 gives a charming 102 error code
on the screen and stops there. I had tried my self and succeeded on W0 complex
to use it with 31MHz OSC but completely failed with W1 complex.
Mr. S's initial attempt was adding a sub-board with 60MHz OSC and shifting
OSC from 50MHz on the complex to the added OSC on the sub-board manually right
after the system finished POST. He succeeded but it was not so easy to shift
OSC from A to B on a working system manually. Then he examined BIOS if there
were any chance to use a higher rated OSC on the complex. He analyzed the BIOS
and its "algorithm" (please don't ask me what it is) then reprogrammed to skip
102 ERROR. His 61-W1B with his reprogrammed BIOS EPROM run successfully in
32MHz base clock without 102 error. I was given his handmade ROM on 1998 Jun
25. His magic really worked on my 5561 too. Type-2 H'ish Japanese complex run
in 32MHz system clock and drove AMD 5x86 around 130MHz speed with 64MHz
OSC.
It was nothing but a magic brought with logic.
Evil whispered to me " Find a Type-A
DX2/66 for him and ask him to modify Type-A BIOS."
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