27 May
2005
27 May
'05
1:47 p.m.
>>>> "der" == der Mouse <mouse
at rodents.montreal.qc.ca> writes:
> Some disks had parallel heads too -- the CDC 6638
is 12 bits
> parallel.
der> I'd even say that _most_ disks have parallel heads, though they
der> generally throw away that parallelism. (I don't know why; the
der> most plausible reason that comes to mind is a "buh-but that's
der> not how disks work" mindset.)
Maybe, but probably not. More likely the answer is "it cost a lot (in
1970) to build N read/write channels rather than just one". With
serial data, you just have one read/write channel, and someplace very
close to the heads you run that through a switch to connect to one of
N heads. For parallel operation, you have to duplicate a lot of
logic. Today that's just one chip, but not so in 1970...
paul