From: Spiro Trikaliotis (ml-cbmhackers_at_trikaliotis.net)
Date: 2005-05-04 21:46:02
Hallo,
* On Wed, May 04, 2005 at 08:13:58PM +0200 Patrycjusz R. ?ogiewa wrote:
> Could it be that there were other devices that required writing the
> value again? Some pre-historical drives or so? Or could the the
> original docs be saying something: "the value written to the register
> will remain in effect until changed/stopped but don't count on this as
> it may change with future implementations of the write logic" - Yeah a
> pure speculation of course...
Yes, this is pure speculation. I cannot add to this, as I have no
experience with the IEEE devices.
> >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.
>
> You mean the two padding bytes, right?
Exactly.
> 1. Two BVCs are required to correctly "close-up" the track write
> process because the first one checks if the previous rather then
> current byte got written
Correct.
> and since those are pad-bytes there is no need to change anything
> in-between
Correct, too.
> 2. The ROM formatting routine does this correctly, yet the ROM sector
> write routine has a bug, which can make the last two bytes of a sector
> be different from what they were left at by the formatting routine
Yes, this is another correct statement. ;-)
> 3. In fact, every sector write should be closed up by the two BVCs if
> we want to do it properly
Well, yes, although opinions might be different here. I believe every
write should be closed up with two BVCs. Anyway, this is not really
necessary as no-one ever tests these bits. Thus, opinions may vary here.
Regards,
Spiro.
--
Spiro R. Trikaliotis
http://www.trikaliotis.net/
http://cbm4win.sf.net/
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