ruud.baltissen_at_apg.nl
Date: 2009-01-26 08:15:50
Hallo Jim,
>
http://www.zimmers.net/anonftp/pub/cbm/manuals/drives/1541-manual.txt.gz
,
Quite obvious place to look, why didn't I think of it? Anyway many
thanks!
> Why is the number limited to 6:
Hmm, indeed hard coded, but not the way I expexted.
> I implemented REL file support on uIEC .....
Maybe I can tell you how I implemented it in CBM-HD, the project where a
PC emulates an IEEE-drive. I must have read the info you gave me years
ago and knew that 'only 720 records' was too limited for a 8x50 drive.
My first version was quite simple. The idea behind it was that if I
needed record X, I simply had to start at the first sector and the go
through all successive sectors, using the T/S info at the beginning of a
sector, until I hit the right sector. This is undoable on a mechanical
drive because of the unacceptable time delay caused by the mechanical
drive. But doable for an harddisk.
My second and final version makes use of side sectors (SS) but in a
completely different way then the 1541 does. Each SS can be succeeded by
another one; the first two bytes contain the T/S info of this successor,
just like with SEQ and PRG files. And each SS contains the pointers to
127 records. For example: needing to check the 1000th record now you
only need to read 5 sectors instead original 1000 (assuming the record
length = 254).
Is this 1541, 4040, 8x50 (or whatever) compatible? Surely not! But All
REL files related software I encounterd so far worked fine.
> Howver, if you're adding this to a list of things to do, I would
> put it *way* down on the priority list.
I will. After reading the info you gaved me and remembering how I did it
in CBM-HD, I was tempted to give it a go, but only for a few moments.
Although I'm working with the 1541 sources for many months, I only
understand a small part of it. For example I know where the P command
for relative files stores its data but I have no idea where the routines
that create the records read this data. How can I expect to change
software if I don't understand it?
But AFAIK you wrote your kernal from scratch on and therefore you're not
limited by original routines. So I wish you success and luck with your
work !!!
--
___
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/ / |_/ Groetjes, Ruud
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\___| URL: Ruud.C64.org
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