Re: Q:400k disk = Which blocks?

[shack@onyx.southwind.net (Randy Shackelford)]

Dave Althoff (dalloff@freenet.columbus.oh.us) wrote:

: Okay, so I want to directly access a 400k 3.5" disk using the ProDOS block
: read command.  Can anyone tell me which blocks I need to read?  Is it, for
: instance, all odd-numbered blocks, all even numbered blocks, the first
: half of the disk...or what?

Gee, I was gonna format a 400K ProDOS disk then run a block editor on it and
check it out. 'Cept you can't format a 400K disk under 6.0.1. Mac system 7.5
won't either. I tried to write a 400K disk copy image to a disk then erase it
on the IIgs but that didn't work. Erasing it as a ProDOS disk on the Mac made
it 800K. So I gave up and put my original Mac system 1.1 disk in and ran a 
block editor. It would read blocks 0-799 and gave errors from 800 up. So, as 
a fellow might have guessed, 400K disks use the first 800 blocks, i.e. the 
first side of the disk. If I remember right from cracking open my Mac 128 and
Lisa, the head of a 400K drive reads/writes to the bottom side of a disk.
--
Randy Shackelford
shack@southwind.net