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Keyboard BIOS AMIBIOS chip help

KLund1

Veteran Member
Joined
Jun 22, 2012
Messages
545
Location
Livermore, CA
Hi
I received this 386dx-40 board. It boots but has no keyboard input. As easily seen in the picture, the keyboard bios chip is bad. It is melted in the middle.
That chip label shows
AMIBIOS
AmericanMegatrends
Keyboard c1992
AA0105829

The retroweb has this board as unidentified, and no keyboard bios dump. (I'll upload good pics when I get this board working, and upload bios dumps when I get my minipro working again)

Any suggestions on replacing this bad keyboard BIOS chip?
 

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modem7

10k Member
Joined
May 29, 2006
Messages
10,286
Location
Melbourne, Australia
Any suggestions on replacing this bad keyboard BIOS chip?
In the photo, I see "8042" printed beside the chip. So this chip, from a hardware perspective, is quite standard - an 8042 or 8742 (EPROM version of 8042) general purpose microcontroller that has been programmed with code that makes the 8042/8742 perform as a 'keyboard controller'. Same as what is done in the IBM AT (IBM 5170) - see [here].

There are people/companies at [here] that can supply and program 8042/8742. (I know, because I am one of them.)

The question is in what code to use. The code from the 8042/8742 used in the IBM AT has a reasonable chance of working on your motherboard. You can see by the 'self reminder' rows at [here], that a crude test shows that it basically works on some 386 and 486 motherboards of mine. Lacking would be PS/2 support (and more?)

Someone has probably already dumped the AMI code from the keyboard controller on a similarly dated motherboard of theirs.
 

NeXT

Veteran Member
Joined
Oct 22, 2008
Messages
8,056
Location
Kamloops, BC, Canada
My question is what caused the chip to smoke itself in case the replacement does the same. It sat there for quite a while as well.
 

KLund1

Veteran Member
Joined
Jun 22, 2012
Messages
545
Location
Livermore, CA
Thanks,
I had a battery damaged 386 hat had a similar dated, same size keyboard chip. I swapped that in, and the board booted up and the keyboard works perfectly.
ALL good now.
I've lost count, but many thanks once again to modem7 !!! :)
 
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