View Full Version : DIY Kaypro 4 '83 harddisk controller

May 22nd, 2017, 09:45 AM

I have been pondering about using a WD1002-27x controller (PC XT) as harddisk controller for a Kaypro computer (the version without the harddisk option).

The WD1002-27x came as a 'hardcard' unit for an XT computer complete with a 30 MB Kalok drive. Needless to say the Kalok drive is dead..
I have a nice full height 5.25 10MB Seagate MFM drive which is fully working and this would also fit nicely into the Kaypro (discarding one of the full-height floppy drives).

Already tested the controller connected to an Arduino as proof of concept to make sure I understand how the bus interface can be made to work (it already does, I can send commands to the controller and the drive is moving the head etc...) However the hardware interface and thus the IO mapping is different than that of the WD1002-HDO controller.

The WD11C00 chip uses only two IO ports to control the complete system (and two more for the config jumpers and reset), the original controller has 8 IO ports mapped.
Getting the XT WD1002-27x controller mapped into IO space of the Z80 is not a problem.

Having disassembled the Kayplus rom I already found some IO instructions for the original controller and they can be modified or diverted to new code to control the 27x, there is plenty of space at the back of the rom so even the kayplus rom entry points can stay the same if needed.

But I have some questions about the original (HDO) controller:

Does it use interrupts and/or DMA to transfer data or is the CPU just reading the bytes from the buffer ?
Is there a circuit diagram for the WD1002-HDO controller? (I have Kaypro service manuals for the computer)
Anyone else tried something like this? :-)