7 Sep
2007
7 Sep
'07
11:18 p.m.
Let's be clear here--I interpret 5.25 DD to be
360K (250K data rate
at 300 RPM) at 48 tpi. And "quad" to me is the same data rate but
narrower tracks for 96 tpi and 720K. AFAIK, the only difference
between DSDD and DSQD was the supposed certification provided by the
mnaufacturer. I never found any difference at all.
When the PC was the only current machine with 5.25" drives, I bought
several boxes of name=brand 5.25" DD disks that would format reliably as
40 cylinder disks on a PC and similarly on other machines (and which are
still readable), but which would not format reliably as 80 cylinder disks.
And yes, I am clueful enough not be be complaining they didn't work as HD
disks on a PC/AT. What I a talking about is formatting them as 80
cylinder disks on BBC micros, TRS80s, etc.
I assume it was something like an increased background noise level. I cna
think of no other explanation.
Incidentally, I was given a couple of plastic carrier bags full of
bulk-erased DEC RX50 disks. Although these were only ever indended to be
used as signle-sided disks, I have never had one fail to format 80
cylinders _double_ sided.
-tony