CF cards on classic machines (was Re: Another disk imaging project)
pkoning at equallogic.com
Fri Aug 5 10:05:10 CDT 2005
>>>>> "Roger" == Roger Merchberger <zmerch at 30below.com> 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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