fat16lib:
I have this Maple version of SdFat Google Code Archive - Long-term storage for Google Code Project Hosting. and it doesn't use DMA.
Oops! Well, that's embarrassing. I was under the assumptions a) that the Maple port used DMA, and b) that someone else besides yourself had done the port! 
fat16lib:
I have examples of Kinesis SPI DMA and plan to try it but it won't help much.SD, DMA, and SPI don't work too well together. The problem is the SD SPI protocol. SD cards indicate busy in SPI mode by holding MISO high so you can't just setup a DMA transfer and go away. The protocol uses control tokens in the data stream which is a pain.
Oh well, at least I've learned something. Anyway, thanks for your continuing support on both these fronts!