PCs that support only one floppy drive in hardware

[Tony Duell]

> But does that work without digging in further?  Does a PC/XT-era floppy
> card replicate a PC-AT diskette controller?  I am asking, since I've
> never tackled such a project.

Sort-of. It uses the same I/O addresses and DMA channel for the 765 and 
the drive select register (the drive select and motor-on bits for drives 
2 and 3 are documented as 'reserved' in the PC/AT docs :-)). What it 
doesn't have is the data rate register, the PC/XT controller is fixed at 
250kbps only. And the data separator is strictly MFM only I think.

-tony