Re: 1571 blocks free

From: Spiro Trikaliotis <ml-cbmhackers_at_trikaliotis.net>
Date: Sun, 26 May 2013 21:21:10 +0200
Message-ID: <20130526192110.GG9312@trikaliotis.com>
Hello,

* On Sun, May 26, 2013 at 09:03:37PM +0200 silverdr@wfmh.org.pl wrote:
 
> AFAIR 1541 reads the "blocks free" bytes from the BAM area and sums
> them up but it skips the directory track when calculating them so free
> blocks from track 18 are not included.

damn, you are right, I am getting old anyd my memory is getting bad. I
just checked the disassembly ($d075 calculates the number of free
blocks): The 1541 skips track 18 ($d087-d08a skip calculation if we are
just checking track 18).

> > I would expect the 1571 to behave accordingly. But: I do not know for
> > sure, it is only a guess.
> 
> 1571 supposedly does the same for track 18 but it wastes almost whole
> track 53 and allocates in the BAM. Hence the question: why bother
> allocating if those blocks are not taken into account anyway? Maybe
> because in 1571 "blocks free" AND/OR other routines don't know that
> this track is now used for extended BAM?

The 1571 executes $d075, like the 1541, but then executes at $a951 for
the second side. ($d097: jmp $a951)

In the loop $a96d-$a97a, I cannot see any special handling for track 53.
I cannot see any special handling for it in the preparation $a962-$a967.
Thus, I would think that for the 1571, track 53 is fully taken into
account, that is, no special handling occurs (or I am blind).

Thus, I must correct myself.

Regards,
Spiro

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Received on 2013-05-26 20:02:05

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