13 Aug
2008
13 Aug
'08
12:36 p.m.
----------Original Message(s):
Date: Wed, 13 Aug 2008 09:49:02 -0700
From: "Chuck Guzis" <cclist at sydex.com>
Subject: Re: Upgrading early BIOS
On 13 Aug 2008 at 9:12, Eric J Korpela wrote:
The concept of "cable select" hadn't
been invented when this machine
was built. Use master/slave.
Is not the operation of "cable select" a function of the cable and
not the mobo? If the OP is using a "cable select" IDE cable, he can
use CS with no problem.
That business with him mentioning CS is what made me wonder if he
wasn't also using a UDMA cable (which by the standard also supports
CS). (It's starting to get pretty hard to find *new* non-UDMA cables
nowadays). If that's the case, then any UDMA-capable drives will be
operating in that mode, which will not work with his old system. If
he's using non-UDMA drives, then the cable won't matter.
Cheers,
Chuck
---------------Reply:
AFAIK cable select has always been an option with Parallel ATA drives,
although it was rarely used in pre-UDMA days; the cable was obviously
different (40 conductors with standard connectors vs. 80 conductors and
unique special connectors) and the order of the drives was usually reversed
(i.e. the slave on the end of the cable).
It's the motherboard that determines the cable type and mode from pin 34,
which is grounded at the mobo end in a UDMA cable, so if the mobo isn't
UDMA-aware I don't think the drives would be, and the cable wouldn't matter.
Also, not all drives supported CS.
Bottom line: don't use CS with pre-UDMA drives, cables and/or motherboards
unless you're certain that all three support it, and even master/slave can be
problematic with very old IDE drives.
More info:
http://en.wikipedia.org/wiki/Integrated_Drive_Electronics
m
13 Aug
13 Aug
1:49 p.m.
On 13 Aug 2008 at 15:36, M H Stein wrote:
AFAIK cable select has always been an option with
Parallel ATA drives,
although it was rarely used in pre-UDMA days; the cable was obviously
different (40 conductors with standard connectors vs. 80 conductors and
unique special connectors) and the order of the drives was usually reversed
(i.e. the slave on the end of the cable).
Nope--I've got a couple of very early Conner and Maxtor drives (less
than 100 MB)--CS isn't an option on the jumpers.
It's the motherboard that determines the cable
type and mode from pin 34,
which is grounded at the mobo end in a UDMA cable, so if the mobo isn't
UDMA-aware I don't think the drives would be, and the cable wouldn't matter.
Also, not all drives supported CS.
Read the Wiki article you cited:
"Pin 34:
Pin 34 is connected to ground inside the blue connector of an 80
conductor cable but not attached to any conductor of the cable. It is
attached normally on the gray and black connectors".
On UDMA-66 capable drives, it's the cable, not the mobo that dictates
speed. Put an ordinary 40 conductor cable on a UDMA-capable drive
and mobo, and the configuration won't take advantage of it. When the
changeover was in progress, we used to get support calls quite often
on the subject of UDMA cables and drives on non-UDMA mobos.
Similarly:
"With the 40-wire cable it was very common to implement cable select
by simply cutting the pin 28 wire between the two device connectors;
putting the slave device at the end of the cable, and the master on
the "middle" connector. This arrangement eventually was standardized
in later versions. If there is just one device on the cable, this
results in an unused "stub" of cable, which is undesirable for
physical convenience and electrical reasons. The stub causes signal
reflections, particularly at higher transfer rates."
Bottom line is that if you use a non-CS-capable (i.e. 40 conductor
"straight through") cable, it won't work. Depending on what the
mobo/controller end does with pin 28, you'll have either two masters
or two slaves on the same cable.
Cheers,
Chuck
5976
days inactive
5976
days old
1 comments
2 participants
participants (2)
-
cclist＠sydex.com -
dm561＠torfree.net