Laptops, realtime audio & ACPI

I just recently bought a second hand Centrino based Toshiba laptop. It's the Satellite M35-S359 model, with a 1.4 GHz Pentium M (Centrino) processor.

I'm pretty happy with it so far. The screen is lower resolution than my old Thinkpad (1600x1200), which is taking some getting used to in Traktor. I'm used to being able to see a much larger playlist. But, the Toshiba can hold far more RAM (as much as 2 GB), and its performance in Traktor is pretty stellar. No problem to do HQ time stretching on both decks.

So the point of this post is to discuss optimizing XP for pro audio, and the issue of ACPI. My experience has been -- and most Windows 2000/XP audio "tweak guides" will agree with this -- for the best realtime multichannel audio performance, you need to disable ACPI by installing XP as a "Standard PC" instead of "ACPI PC". Otherwise, because of the interrupt sharing ACPI requires, you may get crackles and odd sound artifacts when least expected, instead of smooth low-latency audio performance.

Personally, I have experienced these symptoms on several different systems & audio interfaces, which have generally been resolved by reinstalling Windows without ACPI. Currently I'm using the M-Audio Quattro USB.

I had no problem installing as a "Standard PC" on my old Thinkpad, but with the Pentium M/Centrino there seem to be all sorts of things that don't work without the ACPI drivers. I can live without a battery meter (since it's always plugged in), or without the CD buttons on the front of the laptop working. But for example, the display brightness is really suffering.

I did a 2nd XP install on another partition to use for everything else, since i like to keep the audio partition clean. I installed all the ACPI related drivers and crap from Toshiba, and the display is about 3x as bright. So apparently there is a power management feature that regulates panel brightness (not surprising), that seems to be on a miser setting by default.

In the "power options" control panel i set the scheme to "always on", to keep the CPU speed maxed out, but this doesn't seem to affect panel brightness.

Anyone run into something like this, and find a work-around? I'm also interested in the larger discussion here, as to whether disabling ACPI is still necessary with Centrino laptops. Since this cpu & chipset were designed from the ground up to be mobile, maybe the interrupt sharing isn't as much of a problem.

If you're using Traktor 2.5 with all the features on a laptop, are you using ACPI? Having any sound or latency problems?

 

I'm a Toshiba M30-154 (Centrino 1,4) user (I'm closer to you in this matter) so I'm interested too in Centrino performance.

The laptop goes well for me, with a XP PRO clean install with SP1 and without Toshiba crap or other Microsoft updates (I havn't tested if new updates help on performance, yet) I can use Traktor 2.5.3 with the follow soundcard settings:

emi 2/6 at 20 ms with High Quality Timestretching
(at 10 ms it get some crackles)

emi 2/6 at 4 ms with Medium Quality

I'm not on 'standard PC' mode, so I'm interested in your results without ACPI

Also, I'm using an Oxgen 8 and external mixer.

I've benn using 'performance' on 'administrative tools' from XP, but there's no difference in processor load between my Audio partition (ACPI, no network, no internet, no infrared, no wireless, no modem, no printer, removed tons of services), and Toshiba Crapped XP. The only difference is more crackles and pops in the second. Is that IRQ sharing?

I've also used Tweak UI on audio windows. That's a great utility, but get no better performance.

 

Have learned a couple things from recent research that has me rethinking my "ACPI = bad" conclusions.

(1) ACPI is said to be much better in XP than in Win2K. Apparently all devices will no longer share IRQ 9, like in 2K.

(2) Recent generations of both desktop motherboards, and virtually all semi-recent laptops have an APIC (advanced programmable interrupt controller). These boards actually offer 24 interrupts under XP & ACPI rather than 15.

So it sounds like using "Standard PC" mode is really a thing of the past, best left for older computers (like my 440BX based Abit BH6 system that is still chugging along) running Windows 2000.

I'm going to give this a shot, will let you know my experiences.

Some good references:

RME
staudio.de
musicxp.net

 

You're right, but I wanna make two points:

1. ACPI is better in XP than in 2000, ok, but still causes sharing the IRQ where is alloed audio card (IRQ 11 in my lap, and, therefore, in yours too).

I got TEN devices on IRQ 11!!!!

2. Correct me if I'm wrong, but our lap doesn't have APIC. Then, this is not a solution for us

The fact is: My sistem goes well, I have no 'problems' with it, but... what makes clicks and pops appear? I'm looking for a bottleneck, 'cause my processor doesn't raise above 40% when I'm at 4ms with HQ timestretching. What is that? IRQ sharing? USB speed??? With medium TS my system works flawlessly, at 4 ms!!! so, if the thing is on Time stret., and CPU is on 30-35%... what the hell causes crackles???

 

Oops, it looks like you're right about the Toshiba laptops not having an APIC.

I will compare performance on both an ACPI and Standard PC partition on my lappy. I'll also check to see if i'm getting the dreaded IRQ stacking on the ACPI partition.

From my limited experience, I do associate the clicking & popping you describe with PCI bus congestion due to IRQ stacking. That was my experience on two different systems (1 = 440BX desktop, 2 = P3M-based IBM laptop, both running Win2K). Both systems became much better behaved after switching from ACPI to "Standard PC", and the IRQ assignments were made by the BIOS instead of OS.

However, you can of course get the same bad click & pop behavior from trying to run your audio interface at a lower latency than your hardware or drivers will support.

What audio interface do you use? ASIO drivers?

 

I use a emi 2/6, with ASIO.
They say it's 0 latency

 

Does the emi 2/6 driver (or traktor) allow you to raise the latency?

 

Yes. I put it at 20ms with HTS, and 10ms with MTS, thought it works good at 4ms with MTS