> I, IIRC, have seen about 400 kbytes/sec and others have verified
> this number. Still, it's much above your 1 kbit/sec figure

I use SD cards for dsPIC .wav storage and find even retrieval with
SPI has a disappointingly low ceiling

Reading one file of  44100Hz, 16-bit stereo (176.4 kbytes/sec) is
OK but when trying to read much faster reliably you run into latency
problems in the card controller, as Martin says. SPI is not the native
comms for an SD card and presumably the card controller just can't
keep up translating SPI to its 4-bit parallel O/S. In bursts you can
read up to 350-400 kbytes/sec but it's not sustainable, unlike the
transfers seen between say PC and card via a proper reader/writer
which uses 4-bit parallel
--=20
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