CF cards on classic machines (was Re: Another disk imaging project)

Paul Koning pkoning at
Fri Aug 5 10:05:10 CDT 2005

>>>>> "Roger" == Roger Merchberger <zmerch at> writes:

 Roger> Rumor has it that Jim Brain may have mentioned these words:
 >> Paul Koning wrote:
 >>> No... the classic PIO mode IDE registers are 8 bits wide, not 16.
 >>> Some devices may allow 16 bit access as an optimization, but 8
 >>> bit accesses is all you need.
 >> The IDE command registers are all 8-bits wide, but the Data
 >> register is 16 bits wide. You have to support a 16 bit transfer in
 >> order to get the data from the sector buffer (256 16 bit transfers
 >> nets you 512 bytes of data, the IDE std sector).  IN the newer 48
 >> bit addressing mode, the LBA registers grow from 8 bits to 16 bits
 >> as well.

It's almost time for 48 bit LBA for flashcards, but not quite yet...

Curious.  I have some code here that usees 8 bit data buffer accesses
on one platform, and 16 bit accesses on another.  The one I usually
run is the 16 bit case, but last I knew the 8 bit case still


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