DOuble-stepping BBC drives

Tony Duell ard at
Sun Aug 5 15:30:34 CDT 2007

I should know this, but I can't easily find the answer...

I have a BBC B+ with (1770)DFS (V2.x)( and ADFS (V3.5x) (or at least I 
think those version numbers are right). It is cabled up to a single 80 
cylinder double-sided disk drive. 

I wish to read some files of a 40 cylinder (DFS) disk. I seem to remember 
there was a command that would cause the drive to double-step, but only 
allow reading. What is it?


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