2.4.18 kernels: no DMA w/ServerWorks LE chipsets

Josip Loncaric josip at icase.edu
Fri Aug 2 06:11:32 PDT 2002


I've just noticed that our Supermicro 370DLE motherboards with
ServerWorks LE chipset and dual UltraDMA/33 EIDE interfaces do NOT
enable DMA on ide-disk devices (under kernel 2.4.18-5smp, RedHat
distribution).  This is puzzling, because DMA worked just fine until
recently (I think).  Unfortunately, enabling DMA manually under the
2.4.18-5smp kernel ("hdparm -d1 /dev/hda") can lock up the system. 
Apparently, others have had this problem too
(http://www.uwsg.iu.edu/hypermail/linux/kernel/0206.0/0518.html thread
speculates that 2.4.18 drops out of DMA due to a hardware bug in
ServerWorks OSB4 which at least some older kernels did not trigger).

As a consequence, we get only 3.5-4.5 MB/s on these disks instead of
12-22 MB/s which should be the norm.

It appears that this new kernel problem has not been fixed yet... 

Dr. Josip Loncaric, Research Fellow               mailto:josip at icase.edu
ICASE, Mail Stop 132C           PGP key at http://www.icase.edu./~josip/
NASA Langley Research Center             mailto:j.loncaric at larc.nasa.gov
Hampton, VA 23681-2199, USA    Tel. +1 757 864-2192  Fax +1 757 864-6134

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