Very Computer

1. writing to Ultra DMA disk & skips when using sound card

Hi.

I'm using Debian 2.0 & Linux 2.0.36.
I have three big UDMA drives, a 10Gb Conner, a 10Gb WDC and
a 12Gb Quantum Bigfoot. When writing on the Bigfoot drive,
I almost certainly get skips when playing mp3 music. Writing
and playing works fine on the other drives, so it can't be that

It seems like the cpu never gets a chance to handle interrupts
when using the Quantum drive.
'hdparm -u 1 /dev/hdx' (interrupts enabled) doesn't help either.
hdparm doesn't allow the '-d 1' (dma on) switch.

Now, it looks like UDMA is not really supported by the 2.0.x kernel,
so I tried the 2.1.131 kernel to see if possibly faster transfer
rate using UDMA would avoid the problem by transferring the data before
an interrupt occured (assuming this is the problem). It actually
seemed to fix the problem, but the kernel hangs miserabely if issuing
the following for a simple benchmark for writing a 100Mb file:
'time dd if=/dev/zero of=t.t bs=1k count=100000'
This works fine in 2.0.36 at least, although I get the skips in music.
I'm using Alsa 0.2.0 as it seems to skip less than the ordinary sound
driver (also less than the commercial OSS driver).
The 2.1.131 kernel breaks a lot of other things like networking
(route add doesn't work for instance), as well as masquerading
(other configuration tools), so I'm not that eager to try an
experimental kernel again unless it works of course! ;)

The Ultra-DMA mini howto (v2.0.7, August 1998) talks about applying
a patch to the 2.0.35 kernel in order to apply ultra DMA,
but 'patch' fails with all the patches provided.
Is there an updated version somwhere that uses 2.0.36 ?

Please help!
Thanks!
/ Heikki

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