I've done an ATA IDENTIFY on several high speed CompactFlash devices, using True-IDE mode, and none of them report any DMA capability at all. This is a bit worrying. (ie, 2GB Lexar Media drives for example)
The CFA 3.0 spec is confusing in this regard. Sometimes it says that DMA modes are supported, but at other times other times there are implications that DMA is not supported. For instance, section
6.2.1.6.11 has the line "Bit 8 shall be set to 0. Read/Write DMA commands are not currently permitted on CF cards."So what's the scoop here? Am I just unlucky and am trying a whole lot of fast CFs that are only fast when used with PCMCIA? Are there CFs out there that support UDMA-2 with TrueIDE?
I'm only getting 6MB/s with PIO-4, with an optimized copy loop (contiguous sectors, multimode). DMA was supposed to help save this and get more throughput. I'm using the ATA controller on an MPC5200 cpu.
-- Darin Johnson