1581bootblock


by Phil Anderson

    For sometime I have been trying to figure out a way to protect the boot
sector on a 1581 disk from being overwritten when files are written to the
disk The Bootmaker program on the test demo disk allocates track 1 sector 0 in the BAM  Block Allocation Map when the boot is created but the format of
the boot sector is such that no valid directory entry can be made that will
keep a VALIDATE or COLLECT command from deallocating the BAM entry thus
allowing a save operation to overwrite the boot sector  I did write a short
program that reallocates the boot sector and have been using that as an
interim fix.

    The solution has been before me all along Slapping hand on forehead 
Use the Partition Aid  also on the test mdemo disk to create a one block
partition on track 1 sector and then use the Bootmaker to write the boot
sector ignore the nasty remark in the Partition Aid about not being able to
make a partition that size It must be done in the above order, because creating the partition will destroy the boot; do not attempt to open the partition before creating the boot 

    The Bootmaker does not look at the directory it writes directly to the
disk The reason this works is because the drive does not look at the
directory when booting It goes directly to track  sector 0 and reads it  If
the sector starts with CBM it is treated as a boot sector The VALIDATE
 COLLECT command ignores partitions  so the boot sector is permanently
protected  The boot may be removed by simply scratching the partition type
CBM  file and then validating  the disk It is said that some people can see
through a brick wall if they look long enough At least I finally got to see
the wall 


from the Newsletter of the Arizona Commodore Users Group as reprinted in the
Newsletter of the Lansing Area Commodore Club