[Alsa-user] SBlive, midi and ACPI

[<joh...@gm...>]

Hi list,

a few weeks ago I posted a mail into this list regarding a problem with
heavy distorted midisound.

After a lot of digging around with alsa 0.5 and 0.9 I was able to locate the
error. It was (or is) related with ACPI.

My system is Athlon based with a VIA KT266A chipset. As far as Athlons
consume a lot of power I searched and found a way to use ACPI for powermanagement,
which significantly reduces CPU temperature and therefore powerconsumption.
This is done by statically linking ACPI into the kernel and then manipulating
the 'Disconnect Enable when STPGNT Detected' in the northbridge of the
chipset as described in
http://cip.uni-trier.de/nofftz/linux/Athlon-Powersaving-HOWTO.html

But this also is the cause of this unwanted sideeffect regarding my problem
with distorted midi. Playing of midifiles does not generate noticable amount
of CPU load (in top or xosview), and so it seems that the CPU often fells
into the STPGNT state, where it is disconnected from the bus and needs a few
tenth or hundred milliseconds to wake up again, which seems to be the cause of
this heavy distortions.

With deactivated 'Disconnect Enable' bit playing of midifiles runs fine,
even with (the deprecated) alsa 0.5.12a

Just for the records ;-).

Keep up the good work

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