Subject: Re: UDMA downgrading
To: Thomas Hertz <>
From: Kazushi (Jam) Marukawa <>
List: current-users
Date: 10/15/2003 13:40:08
   On Oct 15, 20:14, Thomas Hertz wrote:
   > Subject: UDMA downgrading
   > What is the problem here? I've gotten all kinds of suggestions from a 
   > bad mainboard to bad disks, but none of them seem likely. Would it be 
   > better if I would put the disks in the end of the IDE cables instead of 
   > the middle one? Is somehow raidframe to blame here? I'm confused.

Definetely you should attach a disk at the end of IDE
cables.  If you attach it to the middle, the end of IDE
cable is open and it makes signal reflection.  At the era of
UDMA33, some documentations described to attach a disk at
the middle.  However, now, after UDMA66, all describes to
attach a disk at the end.

However, this may not solve your problem.  I was having
similar problem.  My disks under PROMIS 66 cards were going
to UDMA33 after long heavy run although all disks are
attached at the end.

I think this is just a signal driver problem.  I tried 3ware
6410 and it has similar weakness.  I'm using 7506-8, now.  I
think 7506 series have strong buffer.  I don't have any of
those degration problem after switching 7506 although I'm
using the same drives and cables.

   > Secondly, is it possible to make the driver not downgrade the transfer 
   > mode when it experiences these DMA errors once in a while? They really 
   > only occur like once an hour or so, and that shouldn't be a problem.

It's wonderul if IDE driver worked somehow more
intelligently.  ;-)

-- Kazushi