Re: (u)dma/hdparm question
From: Sven Holm (noemailforusenet_at_hotmail.com.invalid)
Date: 11/01/03
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Date: Sat, 01 Nov 2003 17:35:10 +0100
Felix Althaus <felix.althaus@swissonline.ch> wrote:
>> This is what I get after setting: hdparm -d1 -X34 /dev/hda, so I am
>> using mword2 dma mode for the disk.
>>
>>
>> Before, I was using udma mode4, but my system suffered from random
>> freezing, which are gone now, hopefully (after reducing the transfer
>> mode)
>
>Why don't you use a lower udma mode (like udma3)? Correct me, if I'm wrong,
>but perhaps it then works faster (?)
Yes, I am just testing udma2 instead of my original udma4 and of my
recent tests with mdma2. So far, no freezes. But I need more time to be
sure about this.
>> My question:
>> Is it safe to use a "normal" dma mode (mword2, for instance) for a disk
>> that is udma capable and with a BIOS which is set for udma?
>>
>> My BIOS does only offer udma or non-udma, but no setting for simple dma!
>>
>>
>> Some people told me that setting -X34 is dangerous, because the
>> controller is set for udma, while the disk is now set for dma!
>>
>>
>>
>> I also read the big fat warnings in the hdparm man page.
>>
>>
>> Is it true that I should NOT set a multiword dma mode, but either use
>> udma or disable it altogether?
>
>I read that as long as you get no errors in /var/log/messages while
>accessing hdd (e.g. with hdparm -t) there shouldn't be a problem.
So it is okay to set a simple dma mode under linux even if the BIOS is
set for udma? Once again, I remember those people who told about the
dangers of running the drive in dma mode while the controller is set for
udma...
To the experts:
Is there really no danger/problem in doing this? (mdma2 for drive, udma
for the controller)
If, however, udma2 works all right, I suppose, this should be okay,
since it IS an udma mode, even if my system was running in udma4 before.
Please correct me, if I write nonsense here.
thanks again
Sven
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