Substituting DSHD for DSDD disks (or DS2D if you prefer)

[Curious Marc]

On Jan 26, 2016, at 10:07 PM, Fred Cisin <cisin at xenosoft.com> wrote:
>>> 82901A and the HP 9121D now work great. Quite low capacity (270k?) due to the weird LIF formatting, formats 35 tracks but uses only 33, out of the 40. I wonder why.
>> Partially because the original 5.25" drives (Shugart SA400) were 35 track (#0 - #34), not 40.
> 
> I don't even remember, . . . Does LIF also reserve some space for substitution for bad sectors?
> (there were a higher percentage in those days)
Yes, LIF had two spare tracks. That explains it. 33 tracks + 2 spare tracks matches the 35 original Shugart drives you mention. Mystery solved, thanks.