Saving a File

From: Ruud Baltissen (
Date: 2001-09-20 14:33:14

Hallo allemaal,

When saving a file, the 1541 checks the BAM to see what sector is free.
Actually the 1541 doesn't check the BAM but the memory in $0700/$07FF where
a copy of the BAM is stored.

Saving a file on the harddisk means I need to check and update the BAM as
well. Unfortunately this BAM probably is so big (need 32 KB for every 100
MB) that it is impossible to load it in memory. I could load, update and
save the BAM sector every time I save a sector of the file to be saved but
that is ridiculous IMO.
On the other hand I can load a BAM sector into memory, use it until it is
full, save it to disk again and use another one. After saving the complete
file, the BAM sector is saved again to disk.

So far no problem. But now suppose I have to alocate a set of random
sectors. In this case the Kernal has no idea where to store them in the
first place. It could calculate if the bit of the sector to be alocated can
be found in memory so at least no loading of the according BAM sector is
needed. But it does not know if this is the last sector to be alocated and
so to be sure it must save the memory after each update.

My first question is: does anybody know how the 1581, 8250 and 90x0 handle
this situation?
2nd one: any other ideas?

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 / /  |_/     Groetjes, Ruud
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