31 Oct
2016
31 Oct
'16
7:19 a.m.
On Oct 31, 2016, at 9:55 AM, Noel Chiappa <jnc at
mercury.lcs.mit.edu> wrote:
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
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.