Re: CBM DOS bug?

From: Greg King <>
Date: Fri, 01 Aug 2014 01:03:39 -0400
Message-id: <>
On 2014-07-31 8:35 PM, "Andr Fachat" wrote:
> Hi there,
> I know it's probably well known, but it's later over here... :-)
> I have written (with others) an atmega-based firmware to use as disk
> drive for the PET and other Commodore 8-bit machines.
> During testing of the D64 functionality, I found a small oddity. I used
> VICE with true 4040 disk emulation; and, executed some
> B-A and B-F commands on an image (using a small BASIC test program).
> Our implementation actually has the blocks reserved after running the
> small BASIC test program -- the VICE emulated disk does not.
> It is unchanged from the empty disk it has started with!
> Do you know of this bug? The small test program is here:
> Thanks for any help!

Reread this old message:

Your new symptom is an opposite of the old one; but, they probably are 
related.  I suspect that getting the directory throws away the BAM 
that's in drive RAM.  Therefore, the test program's changes might be 
lost every time it does a "directory".

The fix might be to open "#", "b-a" or "b-f", then close the file before 
doing "directory".

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Received on 2014-08-01 06:00:02

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