DMA difficulties

alvin at Maggie.Linux-Consulting.com alvin at Maggie.Linux-Consulting.com
Sun Apr 14 20:37:32 EDT 2002


hi ya steven

if you have the hdd cable plugged in ( am assuming into the motherboard )
but no ide drive .... you will get whacky results ...
( whether secondary ide is disabled on the bios or not... )

remove cables that dont go nowhere ( is what am trying to say )
remove um if the devices are disabled ..

most bios does allow you to autodetect or user define the
devices... but donno about your motherboard...

the default rh-7.2 kernel should work fine...
( doesnt cough up erroneous messages on boot that i know of..

c ya
alvin



On Sun, 14 Apr 2002, Steven Berukoff wrote:

> 
> Hi,
> 
> Sorry, I should have given a bit more info.
> 
> If the IDE cable is attached, but the power cable is not, the machine will
> not complete POST; it will hang.  If the power cable is attached, but the
> IDE cable is not, the machine completes POST, and goes forward with the
> install.  However, performance is slow.  Only when both cables are
> attached to the CDROM does the installation run quickly.
> 
> To address Alvin's comments, all settings in the BIOS relevant to the
> CDROM are disabled: the CDROM is not listed as a boot device, it's not a
> Master or Slave on either IDE channel, and the Secondary IDE channel is
> disabled.  Further, no IDE cables are attached where they shouldn't be,
> i.e., only the HDD cable is plugged in.  Finally, there is no option in
> the BIOS for enabling/disabling autodetection of IDE devices.
> 
> To address Mark's comments, the kernel that I'm using is the 2.4.7-10
> kernel that comes with RH7.2.  In particular, I'm using the kernel found
> in images/pxeboot, which includes support for the network loopback device,
> initial ramdisk, etc.  Also, the boot messages say that the HDD is
> DMA enabled, although, as I've said, I'm a bit wary of that pronouncement.
> 
> I thought about compiling my own kernel for this, instead of using the RH
> distro version.  However, going through some of the permutations of kernel
> configurations didn't produce a useful product.  Anyone have insights as
> to the kernel config that will work for this, or the options in the stock
> RH kernel, or how to extract such options?
> 
> TIA again for your insights.
> 
> Steve
> 
> 
> 
> > 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
> > alvin
> > http://www.Linux-1U.net
> > 
> > 
> > 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 aei.mpg.de
> > > 
> > > 
> > > _______________________________________________
> > > Beowulf mailing list, Beowulf at beowulf.org
> > > To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
> > > 
> > 
> > 
> 
> 
> 
> =====
> 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
> 
> 
> 

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