DMA difficulties

alvin at alvin at
Sat Apr 13 21:09:18 EDT 2002

hi ya

i notice that when the cable is attached... things goes
bonkers... even if no power ot the drive ( hd or cdrom )

remove the ide cable from the motherboard if its not used

and tell the bios NOT to autodetect ide devices
except those that is in fact present

150 nodes.... hummm .... one full cabinet..front and back.. :-)

c ya

On Sun, 14 Apr 2002, Steven Berukoff wrote:

> Hi all,
> This question may be very slightly off-topic, so I apologize.
> I'm in the process of setting up a network installation procedure using
> PXE/DHCP/NFS/Kickstart w/ RH7.2 for about 150 dual Athlon nodes.  These
> nodes use a Maxtor 6L080J4 80.0GB HDD and an ASUS A7M266-D motherboard,
> among other things.  One particular note is that I don't need/want CDROMs
> in these systems.
> Now, a vendor provided me with a couple of test nodes basically to our
> specifications, except that they included CDROMs and floppies.  To make a
> longish story shorter, I wanted to make sure that the nodes work fine
> without the CDROM.
> So, I first looked into the BIOS.  I disabled (set to "None") Primary
> Slave, Secondary Master/Slave (since my HDD is Primary Master), removed
> the CDROM from the list of boot devices, and disabled the Secondary IDE
> channel.  Then, I passed the kernel args "ide0=dma hdb=none" to try to
> enforce the HDD to use DMA during the Kickstart installation.
> Now, here is the kicker: regardless of the BIOS settings, if I have the
> CDROM plugged in (power+IDE, on the secondary channel) the installation
> takes ~ 5 times faster than if the thing isn't there.  This installation
> includes installation of ~470 packages plus formatting the HDD.  That's
> right, as long as the CDROM is plugged in, everything is peachy, but once
> gone, things slow down.
> I think this is a problem with the DMA settings, b/c when I pass
> "ide=nodma" to the kernel, WITH the CD attached, performance is
> slow.  However, I can't even force DMA to be used.
> If anyone has any suggestions or similar experiences, please let me know.
> Thanks a bunch!
> Steve
> =====
> Steve Berukoff					tel: 49-331-5677233
> Albert-Einstein-Institute			fax: 49-331-5677298
> Am Muehlenberg 1, D14477 Golm, Germany		email:steveb at
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