Ran into an interesting problem while reading a new cart with my sanni clone. I normally connect the reader thru a USB hub and have not had any problems reading/writing carts.
I recently picked up a copy of F1 ROC II (Exhaust Heat) which is a Seta DSP (ST-010 chip) cart. When I first connected the new cart to the reader, the reader could not detect the cart. I modified the code to force dump all of the banks and they were all FFs. I moved the reader to a different PC to run more extensive tests and found it dumped 100% with the original code. The only difference was the direct USB connection vs the USB hub. I moved the reader back to the original PC and bypassed the USB hub and it worked.
I should be getting the other Seta DSP/RISC carts (ST-011/ST-018) so I'll test those out. If anyone has a cart that doesn't detect properly (or dumps all FFs), make sure your reader is connected directly to USB (no hub).