I was experiencing difficulties when using a Compact Flash card for booting a Debian install.
The errors I was getting were:
hda:hda: dma_timer_expiry: dma status == 0×21
hda: DMA timeout error
hda: dma timeout error: status=0×58 { DriveReady SeekComplete DataRequest }
ide: failed opcode was: unknown
… and they would repeat 4 or 5 times with about a 15 second timeout/delay [...]

I was having trouble with Puppy Linux booting on a few PCs I have.  It took a while to find the answer, so I’m posting it here in case others need it.
I was running it on an Intel D201GLY motherboard, but this error doesn’t appear to be specific to that board.  That said, the following [...]