Re: 8250 help needed

From: Nicolas Welte (
Date: 1999-06-06 12:40:13

William Levak wrote:
> > Format an 8050 format disk (single sided). I guess this can also be done
> > with a single m-w command. But which one?
> I have a routine, somewhere, that will convert a 8250 formatted disk to an
> 8050 format.  The format on the second side is still there, but the BAM
> and diresctory are modified to say it isn't.  This works so well that once
> it is done, the 8250 will no longer write to the disk, but only read from
> it the same as if it were formated on a 8050.  If this is what you need, I
> can search for it and upload it.

It is not exactly what I wanted, since I'm interested how a native 8050
disk looks like, not how the 8250 can be fooled to believe it is a
single sided disk. I already have my own idea what the differences are:
2 instead of 4 BAM sectors and of course the second BAM sector looks
different. But if you happen to find your program I'd appreciate a copy
very much. But you don't have to search it actively for me ;-) 

I was also somewhat successful to find a solution for my other question:
the memory location that holds the number of retries and the bump bit.
It's REVCNT (in Olaf Seibert's disassembly) at $10f5. But the drive
happily ignores the bump bit! I found a piece of code that does
something like BIT REVCNT: BVC bump, but it doesn't help. The bump can
be called from another routine as well, and this is where the bump bit
is checked in the 1541, but not in the 8250. So I guess I have to follow
one of the paths Andre suggested if I want to get rid of the bump :-(


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