View Full Version : Specs for IBM Floppy Controllers

May 14th, 2012, 05:08 PM
I am trying to restore my IBM PC 5150 to as close to stock as I can get. I have two floppy controllers, one is numbered 1501484XM and the other is 6181682XM. Is either one or the other a better match for the 5150? They both work fine and are very close in appearance. I am also wondering if one is more capable that the other?

May 14th, 2012, 05:14 PM
The original has some metal-cased IBM hybrid circuits in the data separator. IMOHO, it's a much better controller for reading. The later one uses a digital data separator which isn't quite as good on tough-to-read disks. If you'd like, I can look up the part number for the controller, but I suspect that you know what I'm talking about.

However, IBM shipped the earliest with Intel 8272 (no suffix) FDCs. Because of a peculiar "blindness" after the index, you're better off upgrading that IC to a 8272A or NEC µPD765AC.

May 14th, 2012, 05:51 PM
My 5150 is a "B" model so I doubt it had any first run parts in it. I do see the Intel 8272A chip on the 6181683XM board, and the 1501484XM has a NEC D765AC chip so I guess either one is as good as the other. I am betting that the 6181683XM was originally from the 5150 because the chips that have date codes are 83 and 84 codes, while the 1501484XM has 85 codes. I just bought a 5160 and I mixed-up the floppy controllers while I was troubleshooting a floppy drive problem.

May 14th, 2012, 06:54 PM
Yeah, the part number on mine is 1809115XM408. IC dates are 1981.

May 14th, 2012, 06:57 PM
Thank you for checking.