From: Spiro Trikaliotis (ml-cbmhackers_at_trikaliotis.net)
Date: 2005-05-04 15:39:45
Hello,
* On Wed, May 04, 2005 at 12:39:43AM +0200 Patrycjusz R. ?ogiewa wrote:
> You mean that the byte written to the $1c01 gets written again and
> again until stopped?
Exactly.
> And that re-writing the register doesn't affect anything in the write
> process? Timing?
Well, it changes timing, but in no way that is relevant. As told in the
other mail (some minutes before), even some ROM routines do not do such
a STA $1C01.
> To Spiro:
>
> What was the exact process when you originally noticed the
> problem/incompatibility?
I wrote a probing fast formatter. Then, I added a verify of the just
written track, where I did a byte-by-byte compare if anything that was
read is exactly what was written before. With that compare, I discovered
that the last sector written was always bad. Doing some more analyses, I
found out that it was always the last 2 bytes which were wrong. Thus, I
had this suspicion. I looked at the block write routine in the ROM -
well, it did not do anything other than me. Then I looked at the ROM
format routine again, and discovered that double BVC *. Then I thought
about it, had a look into the 2031 schematic, and I found the reason.
Anyway, I wanted to be sure that my analyzes was right, thus, I asked
here (which includes informing all other people here about that
misconception of the 1541/1571 write process, which seems to be very
common).
Regards,
Spiro.
--
Spiro R. Trikaliotis
http://www.trikaliotis.net/
http://cbm4win.sf.net/
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