I've been fiddling with the SD card driver settings, and now I have 3 drives instead of 4. Maybe I'll have a different number tomorrow.

I've halved the number of tracks, so that each disk holds 8 Mb instead of 16 Mb. That gave me 6 drives instead of 4. But then I added hash tables, which I think will make directory operations faster once I have a lot of files on the disk, and the number of drives dropped down to 3. I was hoping that by halving the disk size then there would be enough memory for 4 drives with hashes, but apparently not. However, there's always a chance I might find some magic combination of settings which lets me do that.

I've also got my mapping programme working, so I can use all 2 Gb of my SD card, by mapping drives to different areas of the card. I'm not sure what the terminology should be. I think it might be accurate refer to it as mounting partitions.

And as well as that, I modified my VHDL code so that my ROM is switched in immediately — it no longer waits for the PCW's boot code to execute. Since doing that, sometimes my PCW doesn't boot, and I have to switch it off and on again. I'm not sure if this is because I've dislodged some wires and the circuit is slightly dodgy, or if the PCW isn't quite ready for full speed operation immediately — the original boot code executes really slowly, which might give things time to settle down, perhaps.

I guess I should switch the VHDL code back and see if it starts being reliable again.