[plug] idebus speed

[Steve Boak]

On Sun, 17 Oct 2004 01:28 pm, Craig Ringer wrote:
> On Sun, 2004-10-17 at 10:45, Tim White wrote:
> > I have a motherboard that I know should be able to run at a higher
> > idebus speed than 33Mhz. It is a E139761 (as far as I can see[1]) and
> > I'm not to sure what I sould try. Should I try booting it with different
> > speeds using knoppix or what? I really want to get the most from the
> > drives that are fairly new.
>
> How are you determining that Linux is running the IDE bus at 33 MHz? If
> you mean the boot message about "assuming 33MHz", My understanding is
> that that is not relevant to the drive access.
>
> If you do wish to examine and possibly change drive settings, you
> probably want to look into `hdparm`. BE CAREFUL, because with a buggy
> drive or controller you can damage your system. It should be safe to
> query the drive with `hdparm $DRIVENAME` and `hdparm -i $DRIVENAME` to
> determine its current settings and capabilities.

I agree with Craig's comments, and add the following:

As always, first RTFM - 'man hdparm'.

If your drive is /dev/hda for example, try 'hdparm -Tt /dev/hda' which will 
give you the cache and real transfer rates for your drive. This is very 
useful to measure any improvements as you try different settings.

As a reference, here's my results for a Via motherboard that I *know* IDE 
interrupts don't work on, no matter what hdparm settings I use:
Timing cached reads:   196 MB in  2.03 seconds =  96.55 MB/sec
Timing buffered disk reads:   12 MB in  3.17 seconds =   3.79 MB/sec

There is a discussion of hdparm and interrupts as it relates to disk transfer 
rates in this list from 17/7/04, subject 'hdparm troubles'. 
Go to the http://mail.plug.linux.org.au/pipermail/plug/2004-July/055240.html
and follow the discussion there. You may find more useful information in the  
PLUG archive at  http://mail.plug.linux.org.au/pipermail/plug, search for 
'hdparm' to look at the relevant messages.

Google will also find you lots of references to disk tuning with hdparm.

Steve

-- 
Ph: +61 8 97560662, IP-Phone: FWD# 454566, e164.org# 61897560662 

"Most men occasionally stumble over the truth, but most pick themselves
up and continue on as if nothing had happened." - Winston Churchill