PCjr (Was Re: IBM PC hacking)

I beleive it is a Xebec. I also have found the same custom hard disk controller chip (the chip that's not the Z80 or the other standard one) on one of the SASI-ST506 Xebec bridgeboards. In fact I repaired such a bridgeboard with a chip taken from an old XT hard disk controller (flame me if you like, the machine the bridgeboard went in was more interesting to me than an IBM PC/XT). I've never tried a Z80 chip on the IBM PC/XT hard disk controller card, so it's possible there's something odd about it. But actually I doubt Xebec would have got a custom-microcoded Z80 processor made for that board, or anything like that (IBM probably _could_ have done. but it's not AFAIK an IBM design). Certainly if that chip failed on one of my XT controllers I'd fit a Z80A and see what happened. -tony