Lee Revell wrote: > One of the JACK developers reported this problem on LKML and the reply > was very interesting, this could explain a lot of the weird latency > issues that laptop users are seeing. > > http://lkml.org/lkml/2004/10/11/182 > > The basic issue seems to be if your laptop has a broken BIOS which > implements ACPI using SMM you are out of luck. Here is some more > information on the problem (near the end of the page): > > http://www.infoworld.com/cgi-bin/displayNew.pl?/glass/bg112596.htm > > If ACPI causes you massive xrun/latency problems then you might have > such a broken BIOS. If you are having weird latency problems with a > laptop, even with ACPI disabled, try to see if it corresponds to the fan > turning on or changing speed. If so then you might be screwed :-( > > There does not seem to be a lot of hope if you do have one of these > broken machines. But we can at least identify the problematic laptops, > complain to the manufacturers, and warn people not to buy them. > My laptop, a Compaq Presario 2516EA, probably suffers from this ACPI disease. However, this has been mitigated by just disabling it; just booting with acpi=off the xrun rate is almost negligible (e.g.running 2.6.9-rc3-mm3-T3 UP). Don't know if the SMM issue is deadly hidden and commanded somewhere from BIOS, then making life a pain, even though apci is off. How can I check this? For the record, I'm quite used for acpi being a real pita, but the lack of it doesn't seem to be much important to me. OK, with acpi=off, I miss battery status, temparature monitoring, whatever, just to name a few goodies, but I buy that for cheap, just about when I get to do low-latency audio. For example, I can do along with jackd -p128 -n2 using the onboard audio (ali5451) without much trouble, iif acpi=off, otherwise a xrun breakbeat is featured ;) Take care. -- rncbc aka Rui Nuno Capela rncbc@xxxxxxxxx
