[En-Nut-Discussion] Nut 3: SD/MMC speed?

[Aaron Burt]

Howdy.
I'm developing a very fast data-recorder.  Ultimately, I hope I can
write 20MB /sec to a 133x CF or SD card, but for now, I'll settle
for what I can get.

Assuming the card is fast enough, how fast can the ethernut write to the
MMC port?  For some perspective, MMC supports a 20 MHz clock, which
means ~2.4 MB/s, and SD supports a 25 MHz clock and 4 bits, giving
~10MB/s.

Can the CPLD get those kinds of clock rates?  It looks like I could
use a state machine to handle the interface and just feed it data from
the CPU or the expansion port.

Also, if I'm reprogramming the expansion port, is the CPLD used for
anything other than SD/MMC and some interconnects?

Thank you for your time,
  Aaron Burt