10 Dec
2003
10 Dec
'03
2:27 a.m.
On Wed, 10 Dec 2003, Patrick Finnegan wrote:
Peter Wallace
On Wednesday 10 December 2003 10:47, Peter C. Wallace
wrote:
No, thats not true, all you need to know is the encoding scheme... The cabling
is interface type specific.
Usually you know the encoding scheme, and I dont
see anything wrong
with using whatever knowledge you have of the interface to optimize
it. If a different encoding scheme is used, an FPGA based design
could easily adapt.
"Knowing the encoding scheme" prevents this from being a "universal"
interface. You'd need to make different version for, say, your PC/XT,
your PDP-11 with an RQDXn, and TeleVideo TS816. (Or shouse I say "my"
as those are all system I have that'd benefit from this). At most, (I
think) you'd need a different cable set for all three of these if you
didn't claim to "know" the encoding.
Also, with at least two of these examples, you probably *don't* know the
encoding method... as mentioned earlier, the RQDX(1) isn't based on any
'standard' controller IC. Also, the TeleVideo's controller is based
upon an 8X300 microprocessor, and may not be RLL/MFM/FM.
The controller implementation doesnt actually matter much. The encoding scheme
is very likely MFM on all the mentioned systems.
But you're right, its probably possible to
undo write-precomp by
simulating the drives tendency to push close transitions apart. I do
think some adjustments are needed per drive type... The write Precomp
value is pretty small - in the order of 5-10 % of the data period.
Peter Wallace
Pat
--
Purdue University ITAP/RCS
Information Technology at Purdue
Research Computing and Storage
http://www.itap.purdue.edu/rcs/