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IBM PC AT missing PALs


New Member
Jun 18, 2010
I have an vintage American Research Corp. 286 (a grate treasure for understanding the hardware part of PC) mobo whith empty DIP sockets for an N82S147 ROM, and 16L8A PALs, in spite of that mobo is a clone of original IBM, i think, that it's schematic is much close, and the PALs from IBM can work in this mobo.Maybe sombody have a reference manual for the IBM AT where the time diagrams of signals is
illustrated.Hopefully it help me to disclouse the structure of PLAs. I haven't any working expirence with PALs, so i very hope that somebody can give me a hint how to read PALs, or can share dumps with me
Best Regards. Vadim


25k Member
Jan 11, 2007
Pacific Northwest, USA
The 82S147 is a bipolar (fuse-link) PROM, not a PAL.

My IBM PC AT techref sheds no real light on the content of either of them. The two 16L8s are used to develop the DMA control signals and the other to control the 80287 interface. The 28S42 4Kbit ROM takes A17-23 and develops the BIOS ROM chip select as well as RAS and CAS for the DRAM array.

The ROM should be easy enough to copy and perhaps the PALs can be copied using the appropriate programmer.