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SubjectRe: External USB2 HDD affects speed hda
David Brownell wrote:

> On Wednesday 01 June 2005 6:23 pm, Mikulas Patocka wrote:
>
>>Didn't you just forget to set H-bit in exactly one queue head? If there's
>>no entry with H-bit set, controller will loop over list of empty heads
>>again and again.
>
>
> Two things:
>
> - Why do you ask that? There's only one QH that _ever_ has that bit set.
> And it's never removed from the async ring.
>
> - The question should be why the schedule is getting turned on in the
> first place, given there's no work for it to do.
>
> Until I have some time available to actually look at this, all I can do
> is answer questions and say "hmm, that's strange" given wierd facts. The
> wierdness here is why that "Async" status bit is ever getting set when
> there's no work for it to do.

I'll be available for testing...

One more data point: I just checked 2.4.31 and it behaves the same.

I also tried checking Windows (98SE) but that may not have been too
useful. It shows no difference in disk throughput with or without the
USB2 HDD switched on, but it's only giving me 28 MB/s anyway (on C:,
which is a 4G VFAT partition right at the end of the disk; the slowest
part) which might not be enough to notice a misbehaving EHCI controller.
Also tried giving it a D: partition at the start of the disk, but the
blasted thing only gave me 16 MB/s there...

Rene.


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