What max capability DM365's SD card?

I believe this is more of a software limitation than a hardware limitation, the most up to date PSP 3.01 SD drivers support SDHC, which by the standard implies a maximum card size of 32GB, I believe the largest the PSP team tests with is 16GB. I see no immediate reason you could not modify the SD drivers to support even larger SD cards, however I have not seen it done, so there may be some unforeseen problem with doing so.

I've taken the liberty of moving this post over to the Linux forum since it has now expanded to be a PSP-related question and not the device's capability.

My understanding is that microSDHC is just a physical form factor change from standard SDHC cards (you can get simple passive adapters to go from microSD to standard SD), so there should be no difference between a microSDHC and standard SDHC from an electrical/software standpoint.