Re: Update IDEJD6

From: Jim Brain (
Date: 2008-04-14 19:14:25

Craig Taylor wrote:
> Just a random thought - use the 1571 u0>h1, u0>h0 commands to indicate which
> portion of the 512 block (eg : 0 = 0-255, 1 = 256-511) ... the organization
> won't strictly be from a "head" perspective but since we're dealing with
> hard-drives I don't think it should matter as much - just as long as the
> capability is there.
> As a further extension, u0>m1 could add an additional bam track for the
> second "side" that conditionally gets considered ....

I stil think 256 byte sectors are the most compatible (How do you 
reference loading from the 257th byte of a sector using B-R or U* 
commands?).  Yes, you can ignore such things, but I think it's trivial 
to handle 256 byte logical sectors in a 512 byte physical sector 
environment.  uIEC and sd2iec do it and it does not take lots of extra 
RAM. 1581 did it as well.

But, I like Craig's idea in another context.  Use u0>h* to move to 
different virtual "heads" in the partition. 

Say, for instance, that you decided to limit partitions to 16MB, as 
that's 255T*256S*256bytes...  You also have 254 partitions, so that 
16MB*256 or 4GB.  You could use u0>h1 to access a completely new set of 
256 partitions as a different drive, using the same drive number.

I think there is a way to reference 255*256*256*256 bytes in a "disk", 
so a partition could be 4GB.  254 partitions would be a very large disk, 
but H1 could double it.


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