6 May
2002
6 May
'02
3:04 a.m.
From: Doc <doc(a)mdrconsult.com>
I've been wondering, based on some old posts to
the CP/M groups. Will
the same disk, for example an ST251, format and work off either an MFM
or an ESDI controller? Totally true, totally false, depends on drive?
For that mmatter, is there a good newbie-level reference for the 2
interfaces? They were history when I started playing with keyboards,
and I never dreamed I'd need to know.
The problem with EDSI was it sued the same cables as MFM IE: the pair
of 26 pin and 34pin. The interfaces however were toally incompatable.
No, a St251 would not interface to EDSI. It will interface to both MFM and
RLL though RLL may/may_not be reliable with that drive. I have used ST225s
with RLL controllers to get ~30mb from them (st225 is 20mb MFM).
Allison
6 May
6 May
3:36 a.m.
On Mon, 6 May 2002, Allison wrote:
The problem with EDSI was it sued the same cables as
MFM IE: the pair
of 26 pin and 34pin. The interfaces however were toally incompatable.
Thanks. I had always thought that, but there are a couple of
references on the *.sys.cpm archives to the effect that someone had
reformatted an MFM drive on an ESDI controller. I thought he must have
meant RLL, but I wanted to check.
Doc
4:53 a.m.
New subject: ESDI (was: free DEC M7555 card
On Mon, 6 May 2002, Allison wrote:
The problem with EDSI was it sued the same cables as
MFM IE: the pair
of 26 pin and 34pin. The interfaces however were toally incompatable.
Allison is, of course, absolutely correct.
ST506/412, what is often sloppily called "MFM" provides a set of signals
for drives that can support either an MFM or RLL encoding. (Well, it
COULD support other encodings as well) MFM and RLL drives could be
interchanged with each other, although many MFM drives could not reliably
do RLL. That did not stop many people from using them anyway, and then
cursing the manufacturer when they wouldn't perform past spec.
ESDI was SIMILAR, but NOT compatible with ST506/412
The problem with EDSI was it sued the same cables as
MFM IE: the pair
^^^^
We live in a litigious society.
of 26 pin and 34pin. The interfaces however were
toally incompatable.
^^
Odd. Mine seem to have 20
9:56 a.m.
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11:37 a.m.
> The problem with EDSI was it sued the same cables
as MFM IE: the pair
> of 26 pin and 34pin. The interfaces however were toally incompatable.
On Mon,
6 May 2002, Tony Duell wrote:
I am sure it was a typo, but to avoid confusion, the
cables for the ST506
interface (and for ESDI) are 34 pin (control) and 20 pin (data).
Or, ...
maybe they changed it out of fear of being sued if they were not toally
incompatable.
[Allison's error rate is low, so that any misteaks that she makes really
stand out]
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ajp166＠bellatlantic.net -
ard＠p850ug1.demon.co.uk -
cisin＠xenosoft.com -
doc＠mdrconsult.com