How to setup DMA on my CD-RW?

[Paul W. Frields]

On Mon, 2003-10-06 at 20:07, Thiago Vinhas de Moraes wrote:
> > >    Does anyone how to do it?
> > 
> > IIRC (this has changed a number of times), you have to make a
> > /etc/sysconfig/harddisk<device> file that contains USE_DMA=1,
> > where <device> is the device of your disk or CD-ROM (such as hdc).
> 
> At least on Fedora beta2, there is only the /etc/sysconfig/harddisks
> file. You are right, there is the USE_DMA option, but it will set DMA
> ON to all the hard disks. Is this a problem?

The /etc/sysconfig/harddisks file is a global settings file that can be
overridden by separate files such as /etc/sysconfig/harddiskhda,
/etc/sysconfig/harddiskhdb, et al. However, this file shouldn't be
needed for basic settings since the kernel does significantly more
autodetection these days. For example, on my UDMA100 system running
2.4.22-1.2087.nptl, with *no* settings in /etc/sysconfig/harddisks:

/dev/hda:
 multcount    = 16 (on)   
 IO_support   =  1 (32-bit)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  0 (off)
 readonly     =  0 (off)
 readahead    =  8 (on)
 geometry     = 4982/255/63, sectors = 80043264, start = 0

Note the equivalent of hdparm's "-m16 -c1 -d1 -u1 -a8" is in play, and I
didn't set a thing. You can verify this both through hdparm (use -i or
-I for more lengthy info) and by checking /proc/ide/[piix|via], for
example. Both my /proc/ide/via and hdparm -i (as well as other tests)
confirm that the drive is running at UDMA-5 (100) speed.
-- 
Paul W. Frields, RHCE