DMA difficulties

[Steven Berukoff]

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 aei.mpg.de