I had bought an AT at an auction sale once. it was the old type 1 board, with 512k and double stacked ram chips. much to my surprise, it was upgraded to the familiar AMI bios, which of course gave it type 47 for user defined drives! should of kept it for that reason. i sold it before i started my collection in 1991 david In a message dated 98-01-24 21:57:20 EST, you write: << Correct. The PC/AT bios only stores a drive code (a number that points to a table in the ROM) in the CMOS RAM/RTC chip. There's no support for storing drive parameters there. That's why there's a kludge ROM in this machine with a patched drive table so I could add a larger IDE drive to it. >>