IBM X21 chip ID

[Quattro]

IBM X21 motherboard. Will not turn on. A chip labelled "ACA 083"s burnt in the center. No other chips appear damaged. Can't find anything at Digikey or Mouser.

I attached a few pics of a working X20 motherboard which seems to have teh same chips. Any idea where I could find such a chip? Anyone have a dead Mobo?

Burnt Chip MoBo (X21):

Pic1: http://www.mnsi.net/~natwhite/1.jpg (CPU mis-labeled)
Pic2: http://www.mnsi.net/~natwhite/2.jpg

Working MoBo (X20):

Pic 1: http://www.mnsi.net/~natwhite/x20_1.jpg
Pic 2: http://www.mnsi.net/~natwhite/x20_2.jpg
Pic 3: http://www.mnsi.net/~natwhite/x20_close%20up.jpg