Re: 1541IDE and 1541IDE-S -- and 8250IDE? (and 64IDE, now)

From: Jim Brain (
Date: 2007-12-14 23:38:46

David Wood wrote:
> I realize this would be slow, but relative to the speed of the IEC protocol,
> why not swap bufferspace into and out of a couple reserved harddisk sectors?
I believe you'd still need a 512 byte sector somewhere, as you need to 
write the data all at once, not repositioning the IDE drive once you 
start (I don't think IDE can seek to a byte in the 512 byte sector.  If 
it could, we could just do that.

But, 1K of additional RAM banked in somewhere where there is no 
ROM/RAM/IO would work fine.  You only need the 512 bytes during the 
write operation.  The tricky part is updating BAM.  How does the 1541 
update BAM now?  Doesn't it use the command channel buffer to read BAM 
into, update, and write it back prior to writing the new sector?  As 
well, when you initially write out the sector, do you set next T&S to be 
0,255, and then go back when you lay in another sector and update?

Still, all of the operations require a reusable 512 byte RAM.


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