Upgrading early BIOS

M H Stein dm561 at torfree.net
Wed Aug 13 14:36:04 CDT 2008

----------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.

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:


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