How to force a PATA HDD to only report PIO transfer capabilities? (DMA hangs firmware on device)

Question

I have an old bit of music kit - the Roland SP-808 (circa 1998) that uses an internal 100 MB ATAPI ZIP drive to store samples rather loudly.

Lots of owners over the years have attempted to replace the drive with compact flash to IDE adaptors and the like mostly unsuccessfully as the firmware recognises the replacement drives but then freezes during read/writes.

The theory I am wanting to test is that the freezing occurs due to the fact that the DDRQ and DDRACK pins (21 & 29) of the IDE interface on the SP-808 are shown in the service manual as not connected meaning the SP-808 hardware is incapable of performing DMA operations - the stab in the dark here is that the original source code used for the firmware didn't take this into account and therefore any device connected that reports DMA capabilities ends up hanging the system waiting on unconnected pin signals.

So my question is how would I go about forcing an old hard drive to only report PIO transfer capabilities? Would this require modifying bytes in firmware or was this something achievable using manufacturer utilities?

Answer 1

One thing you could possibly do is modify the SP-808 firmware to handle this correctly. I'm in the process of hacking the MV8800/MC-909 series.

What does it use for a CPU, a SuperH processor?