Re: Sound & DMA

Alan Cox (alan@lxorguk.ukuu.org.uk)
Mon, 21 Sep 1998 01:56:32 +0100 (BST)


> to a floppy at the same time causes a hard freeze. Unfortunately, I just
> downloaded, patched, recompiled, rebooted and was still able to freeze the
> machine writing to the floppy and playing sound. So, either, this patch
> shouldn't fix that and I'm completely off base, or it didn't solve the
> problem.

I didnt expect it to change anything because the DMA controller was correctly
locked by cli/sti in the cases that people report and because Andrea
reported that he could demonstrate the lockup for VIA chipsets from within
DOS. I have a couple of ideas about this.

Firstly people report that it only occurs on back to back DMA changes. The
VIA chipsets have a FIFO on the ISA bus DMA. So my guess is a udelay()
thats long enough to drain this fifo will magically sort the problem.

Secondly the DMA controller is officially a 2MHz or so part and you are meant
to delay for the poor relic. Of course nobody has actually used an authentic
82xx series component in a PC since 286 days.

Alan

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