RE: 1541IDE and 1541IDE-S -- and 8250IDE? (and 64IDE, now)
Date: 2007-12-24 09:07:07

Hallo Nicolas,

> Adding IDE support to the 8x50 design might be easier than it seems.

I disagree.

> So "only" the FDC code needs to be replaced,

One problem is that some FDC code, like the formatting routine, is found
in the ROM of the Command Controller (CC). So even if the program for
the CC doesn't change, the contents of the ROM does.

> and the DOS2.7 or 3.0 can stay completely unchanged.

Which means we are stuck with a 1/5/7.5 MB harddisk :) To be able to
handle larger disks we have to:
- find the location of the drive parameters and to change them. 
- find out how the CC handles the BAM table as this needs to be enlarged
as well.

But again, the above preperations only provide us with a 16 MB harddisk.

Hallo allemaal,

As already known, to solve this 16 MB problem I came with the LBA-link
soulution, capable of handling up to 128 GB harddisks. But I'm not
really happy with it. Yesterday an idea popped up in my mind which maybe
is worth a discussion or can lead to other ideas: clustering, as used in
FAT and other file systems. 

In this case a Commodore sector will in reality be more then one real
sector. The number of bytes that reside on the last sector can be solved
by either using the third byte as well or using an unused byte in the
directory entry. I realise that this idea has a some disadvantages, for
example clustering 100 sectors to one cluster:
- we still will only cover a 1.6 GB harddisk
- every program would occupy at least 100 * 512 = 51 KB disk space, no
matter its real size
- the size of almost every known program will show up in the directory
in the range of 1 or 2 blocks.

As said, just an idea, but hopefully one that triggers some other ideas.

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