Re: Limit to length of REL file?

From: Marko Mäkelä (
Date: 2009-01-25 20:46:09

Hi Groepaz, Ruud,

On Sun, Jan 25, 2009 at 08:33:22PM +0100, Groepaz wrote:
> On Sonntag 25 Januar 2009, wrote:
> > Hallo allemaal,
> >
> >
> > First an SHORT update on 1541: it seems things run fine with the BAM on 0/0
> > and the directory on 18/x.

Ruud, I hope you keep the code in version control.

> > So I went a step further: not needing to store the label in the BAM, I
> > thought I could use the rest of this sector for more BAM info. So I told
> > the drive it had 63 tracks and 24 sectors/track, for EVERY track. A nice
> > 1123 free blocks. Then I started my test program. After a lot of testing I
> > found out I was only able to create a REL file with 720 records (726
> > blocks), each holding 254 bytes. If there were already other files on the
> > drive didn't matter.
> > If I try to create a greater file, my 1541-IDE hangs up. But... my 1541-II
> > does as well: no flashing LED, motor stops running after a few seconds.
> >
> > Bug? No, but it won't win a beauty contest IMHO.
> tried the same on a 1581 or whatever "bigger" drive? its no wonder the 1541 
> cant deal with a file that is larger than the disk =P

If I remember correctly, bigger drives implement "super side sectors" on top
of the "side sectors" that point to the individual blocks of a REL file.
I can't remember what the size limit might become then.  Most likely not
an entire 16MB disk.

As far as I know, modern disk file systems implement multiple levels of
indirection blocks, as needed.  Each file (i-node in Unix terminology)
is similar to a Commodore REL file; the indirection blocks point to each
individual sector.


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