14 Jan
2011
14 Jan
'11
2:42 p.m.
Tony Duell wrote:
Problaby one of those 6500-series microcontrollers, which were used in
some disk drives...
And it's old enoguh that the Beeb should have taken account of that
design .Perhaps it was just so obscure that nobody over here had come
across it (I certainly hadn't...)
I suppose the question is whether Acorn wanted just anyone connecting any old
drive to the BBC, or whether they'd rather you went out and bought an
off-the-shelf unit (drive, enclosure, and either PSU or power lead for hooking
to the BBC's PSU). They might have been aware of drives with buffered seek at
design time, but assumed that vendors wouldn't supply that type of drive
because it wouldn't work.
Of course lots of people *did* homebrew drive setups for the beeb, but (at the
time the machine was current) the chances of them having one that supported
buffered seek were probably quite low.
(are there documented cases of HH 5.25" drives with buffered seek? I don't
think I've ever seen a FH drive used with a BBC machine)
What happens with one of these drives is you slow the
steppign rate
(at the cotnroller) right down, say to 20ms steps? Does it still
sometimes kil the index pulse?
This is actuall older than one might think.
I've got a FH 5.25"
Micropolis 96 tpi drive that uses buffered seek--it blocks index
until the head is on-cylinder. Probably 1979 or so; I could check
the date codes. It uses a MOS Technology microcontroller (house
numbered). It has a HC51/U-sized 2MHz crystal on the PCB. For pure bad deisgn, nothing beats the Shugart SA4000
hard disk, IMHO.
Heh, I like that. Oops! :-)
cheers
Jules