Promise Ultra ATA 66 controller vs. FC1

[Alexander Dalloz]

Am Fr, den 23.01.2004 schrieb Robert D. Arendt um 22:30:
> Alexander Dalloz wrote:
> > Am Fr, den 23.01.2004 schrieb Robert D. Arendt um 19:18:
> > 
> >>Steve Saady wrote:
> >>
> >>>I have a Promise Ultra 66 eide controller, but think it is only being 
> >>>acessed at 33 Mhz.  I have looked around, but have not found how to 
> >>>ascertain what rate Fedora is using it at.
> >>>Is there a way to configure FC1 to use it at 66MHz?
> >>>
> >>
> >><snip>
> >>
> >>>dmesg|more :
> >>>ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
> >>>
> >>
> >>I added idebus=66 to /etc/grub.conf, so my boot line now looks like:
> >>   kernel /vmlinuz-2.6.1-1.53smp ro root=LABEL=/ apm=off idebus=66
> >>should work with the nominal FC1 kernel as well.  Really boosted my
> >>disk I/O speed.
> >>
> >>Hope this helps,
> >>-Bob Arendt
> > 
> > 
> > What kind of hardware are you running - no PC ware or even very old EISA
> > bus hardware?
> > 
> > idebus=66 is nonsense and might even be dangerous on normal PC hardware,
> > as simply the bus frequency is 33 MHz and nothing else!
> > 
> > How did you measure the speed boost? Please compare the speed at
> > idebus=33 and with your setting of idebus=66 and post your values and
> > how you measured the I/O speed values.
> > 
> > Alexander
> > 
> Alexander - you're right, I'm wrong.
> 
> Hardware: ASUS P4P800 motherboard (865PE+ICH5), 512 Mbyte RAM, 3.0G P4
> hda: WDC WD800JB-00ETA0, ATA DISK drive

Fairly new hardware.

> I used a bash scriptlet to write 1 Gbyte files to the test disk
> 
> rm junk*
> for n in 1 2 3 4 ; do time dd if=/dev/zero of=junk$n bs=8192K count=128; done
> 
> The first time is quicker, due to the OS using available RAM as cache.
> Subsequent files should get the sustained write speed.  I tried repeating
> my tests in single-user boot, and got 20.0 sec/Gbyte, *regardless* of
> idebus= setting.  Now I believe the idebus parameter is irrelevant,
> since the drive is using the udma5 mode, not a PIO mode.
> 
> First time I tried this, I saw 30 sec vs. 21 sec;  There must have been
> some background activity that skewed results;  I should have been more
> careful.

Careful with such settings. As from google research I am warned that
there might be some unconditional damage with idebus=66, data loss and
filesystem damage. I urgently suggest you set it back to default or even
erase the whole parameter setting.

Your system is running with DMA and that is nice. Compared to PIO mode
it is much faster and consume less CPU power at harddisk activities. If
you checked with "hdparm -i hdX" that your DW drive is running at UDMA
mode 5 all is fine. :)

> -Bob Arendt

Regards

Alexander


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Alexander Dalloz | Enger, Germany
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