2.4.18 kernels: no DMA w/ServerWorks LE chipsets

[Mark Hahn]

> enable DMA on ide-disk devices (under kernel 2.4.18-5smp, RedHat

it's worth noting that .18 is fairly ancient (though I suppose RH
may have back-ported the SW changes...)  I just looked, and there
are some non-whitespace changes since .18.

AA also has the following in his patch cluster:
| 51-severworks-ide.bz2
|        Attempt to fix the ServerWorks problem sit certain disks and DMA.
|        Author: Martin Wilck <Martin.Wilck at Fujitsu-Siemens.com>

> 2.4.18-5smp kernel ("hdparm -d1 /dev/hda") can lock up the system. 

in general, hdparm should be considered dangerous in moder Linuxes.

> 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.

indeed 4.5 is bad; most modern IDEs deliver 25-45 MB/s (inner-outer).