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SubjectRe: disk corruptions on "tuned" disks Was: APM killing low-latency performance on BX mainboard
Date
On Thu, 11 Nov 1999, Dan Hollis wrote:
> > thanks, but what is the exact problem source , DMA or unmask IRQ ?
>
> DMA
>
> > I'm watching DVDs for hours ( DMA enabled) without any lockups.
>
> It may be ultra dma only bug. Im not sure. My DVDROM and CDROM both
> support udma.

I don't played with UDMA on CDROMS, only simple DMA.
I don't care about a potential UDMA bug,
simple DMA solves all latency problems, and the performance
difference between DMA and UDMA on a CDROM drive is almost
zero. (since the CDROM is the bottleneck).
The command I usually use to tune the CDROM is :
hdparm -u 1 -c 1 -d 1 /dev/hdc

it is a cheap MASHITA 6x DVD drive:

[root@localhost benno]# cat /proc/ide/ide1/hdc/settings
name value min max mode
---- ----- --- --- ----
breada_readahead 4 0 127 rw
dsc_overlap 0 0 1 rw
file_readahead 72 0 2097151 rw
io_32bit 1 0 3 rw
keepsettings 0 0 1 rw
max_kb_per_request 122 1 127 rw
nice1 1 0 1 rw
pio_mode write-only 0 255 w
slow 0 0 1 rw
unmaskirq 1 0 1 rw
using_dma 1 0 1 rw

>
> > But are you sure that every ATAPI CDROM drive on the planet
> > has this hardware flaw.
>
> Its the controller not the CDROM at fault

are you sured that the BX chipset is flawed ?
It seems to work well.

>
> > I stressed my CDROM drives quite a bit, and was unable to lock up the box.
>
> What controller and what drives

Mainboard Gigabyte GA 6BXD (dual) with BX chipset.

>
> > How is this handled my other OSes ?
>
> They dont run DMA.

Wrong: try to dig on deja.com searching articles about
DVD software playback on windoze:
for most people it is almost impossible to get skipfree video
without DMA.


>
> > > Promise Ultra66. No DMA on CDROM/DVDs. It just wont work. At all.
> > PS: why should recent ATAPI CDROM let you set the DMA mode, when they
> > know that it could lead to problems ?
>
> Its the controller not the CDROM at fault

I was wondering how much % of the controllers are faulty in this respect.

>
> -Dan

Benno.

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