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aeeben
Registered: May 2002
Posts: 46 |
The good old 1541 save @:bug - question
Finally googled the 1541 replace-save bug - so all the three conditions listed here must be met to make it corrupt data:
https://www.c64-wiki.com/wiki/REPLACE
-> If I'm saving a game state or program settings or something, and it's only 1 or 2 blocks, it should be always safe to use KERNAL save with @:filename, because condition #2 ("One or more blocks must get marked as occupied on at least three tracks") is never met?
Please correct if wrong. Please confirm if right :)
@-save slowly rot my programming disks as a kid, so I learned to never use it! |
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chatGPZ
Registered: Dec 2001
Posts: 11540 |
This has been discussed to death - and as usual the wiki page isn't the end of the story.
Just don't use it. Ever.
(your example is missing another bad case: when there are less blocks free than you are 'overwriting' -> boom) |
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TheRyk
Registered: Mar 2009
Posts: 2503 |
Quoting chatGPZ...
Just don't use it. Ever.
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Yeah, i.e. if chatGPZ meant save"@:..." not c64-wiki ;) |
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chatGPZ
Registered: Dec 2001
Posts: 11540 |
of course :D |
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TheRyk
Registered: Mar 2009
Posts: 2503 |
Quoting 'TS'so I learned to never use it!
And I wouldn't rely on ALL of the 3 conditions having to be fulfilled for making error happen...
Apart from direct mode and BASIC, where it's of course easier/shorter than doing it properly with all the OPEN-CLOSE-hankypanky, I don't see any advantage leading to recommending anyone risking SAVE"@..." at all |
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chatGPZ
Registered: Dec 2001
Posts: 11540 |
save/scratch/rename is the way to go indeed. there is no reason to try to work around that bug - there has to be enough blocks free for this in either case. |
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Fungus
Registered: Sep 2002
Posts: 756 |
I traced it out once, and what happened was the 1541 allocates the block in the bam, then when it goes to update the directory, it re-reads the bam into the same buffer and the bam is then corrupted. |
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chatGPZ
Registered: Dec 2001
Posts: 11540 |
That is _one_ of the many problems that exist in various DOS versions :) (The wiki page tries to explain some of the others, but is written in a very confusing and slightly misinforming way imho) |
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Frantic
Registered: Mar 2003
Posts: 1661 |
Is a simple and relatively up-to-date (drive-code-wise) library available somewhere, with fastload/fastsave/fastsave-overwrite/read-dir functionality for use in tools ? |
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chatGPZ
Registered: Dec 2001
Posts: 11540 |
Krills can only overwrite iirc (creating files is a bit complex...) |
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Frantic
Registered: Mar 2003
Posts: 1661 |
I will pay 5 SEK to the person who creates such a library, and 5 SEK more if the code is fairly independent of super specific features of some particular assembler. |
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