> On Oct 31, 2016, at 9:55 AM, Noel Chiappa <[email protected]> wrote:
>
>> From: Don North
>
>> Track 0 is not used by standard DEC software
>
> I wonder why DEC did't use track 0. The thing is small enough (256KB in the
> original single-density) that even 1% is a good chunk to throw away. Does
> anyone know? (I had a look online, but couldn't turn anything up.)
>
> If I had to _guess_, one possibility would be that track 0 is the innermost
> track, where the media is moving the slowest, and as a result it's more
> error-prone. Another is that IBM used track 0 for something special, and DEC
> tried to conform with that. But those are pure guesses, I would love to know
> for sure.
I don't know either. But for what it's worth, this odd addressing carries over
to the RX50. Not exactly, though. Logical block 0 is the first sector on
track 1, sectors are 2:1 interleaved, and there's a 3 sector skew from track to
track. The difference here is that track 0 does get used: it holds the last 10
sectors of the logical address space. In other words, physical track 0 follows
physical track 79.
paul
