Intel Core Duo USB Issue: A Mischaracterized Bug
by Anand Lal Shimpi on February 13, 2006 1:40 PM EST- Posted in
- Laptops
Final Words
First of all, it's important to characterize the impact of the USB 2.0 asynchronous scheduler bug on both Core Duo and Pentium M based systems. Using the Lenovo T60 and T43 as comparison points, we found that without the fix, adding a bus-powered USB device such as a memory stick reduced battery life anywhere from 18 - 28%. In the case of the T43, a 28% reduction in battery life for simply plugging in a USB 2.0 device is beyond ridiculous. In the case of both notebooks, applying Microsoft's fix gives you almost all of your battery life back. The only decrease is due to actual power used by the device and any polling that may be happening as a result of the device being installed.
It is also extremely important that we point out the existence of this bug on all of the platforms that we tested; in other words, this is not exclusively a Core Duo problem. In fact, in the case of the T60/T43, the Sonoma based T43 actually lost a larger percentage of its battery life due to the asynchronous scheduler bug than the Napa based T60. We saw the same results with the ASUS notebooks. With only the integrated USB 2.0 camera connected, the ASUS Napa notebook lost 17% of its battery life due to the bug, while the Sonoma based W5A lost 25.5%. Once again, implying that this is a Core Duo issue alone is simply incorrect; the problem affects Sonoma platforms just as much, if not more, than Core Duo platforms. Based on the results that we've seen in our perfmon analysis, we tend to believe Microsoft's assessment that the problem would exist on any system that spent any time in C3 or lower power states.
Thankfully, the Microsoft fix does seem to work pretty well. The only downside is that the problem re-appears after bringing your notebook out of stand-by. Although a simple reboot will fix the problem once more, it's not a practical long term solution. Unfortunately, we have absolutely no idea when a true fix will be put in place. Until Microsoft releases a fix, we can only suggest that all notebook users, regardless of your CPU, either implement the temporary fix that we outlined in this article or be very conscious of leaving USB 2.0 devices connected while on battery power.
First of all, it's important to characterize the impact of the USB 2.0 asynchronous scheduler bug on both Core Duo and Pentium M based systems. Using the Lenovo T60 and T43 as comparison points, we found that without the fix, adding a bus-powered USB device such as a memory stick reduced battery life anywhere from 18 - 28%. In the case of the T43, a 28% reduction in battery life for simply plugging in a USB 2.0 device is beyond ridiculous. In the case of both notebooks, applying Microsoft's fix gives you almost all of your battery life back. The only decrease is due to actual power used by the device and any polling that may be happening as a result of the device being installed.
It is also extremely important that we point out the existence of this bug on all of the platforms that we tested; in other words, this is not exclusively a Core Duo problem. In fact, in the case of the T60/T43, the Sonoma based T43 actually lost a larger percentage of its battery life due to the asynchronous scheduler bug than the Napa based T60. We saw the same results with the ASUS notebooks. With only the integrated USB 2.0 camera connected, the ASUS Napa notebook lost 17% of its battery life due to the bug, while the Sonoma based W5A lost 25.5%. Once again, implying that this is a Core Duo issue alone is simply incorrect; the problem affects Sonoma platforms just as much, if not more, than Core Duo platforms. Based on the results that we've seen in our perfmon analysis, we tend to believe Microsoft's assessment that the problem would exist on any system that spent any time in C3 or lower power states.
Thankfully, the Microsoft fix does seem to work pretty well. The only downside is that the problem re-appears after bringing your notebook out of stand-by. Although a simple reboot will fix the problem once more, it's not a practical long term solution. Unfortunately, we have absolutely no idea when a true fix will be put in place. Until Microsoft releases a fix, we can only suggest that all notebook users, regardless of your CPU, either implement the temporary fix that we outlined in this article or be very conscious of leaving USB 2.0 devices connected while on battery power.
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Eris23007 - Monday, February 13, 2006 - link
P.S. That's why you read more than just the intro and conclusion pages before asking questions."RTFM"
DigitalFreak - Monday, February 13, 2006 - link
Ha!Eris23007 - Monday, February 13, 2006 - link
The USB hard drive they tested with had its own power supply. The "USB Drive" was a flash device (USB bus powered), while the "External HDD" was:UNCjigga - Monday, February 13, 2006 - link
I will have to do some testing on my notebook with the 'workaround' fix installed. I could have sworn that around the time I installed SP2 on my lappy the battery life suffered, but this was about 6-12 months after I got it so I just figured the battery was getting old.Ionizer86 - Monday, February 13, 2006 - link
Wow, this is getting interesting. I'm surprised that this bug affects 915 based systems too. I wonder if this could be a broader issue that may affect intel 855 systems or AMD-based computers with chipsets from other vendors. I suppose I could do some playing aroundIonizer86 - Monday, February 13, 2006 - link
No edit button... (accidental post before completion).I could test this out on my 855 based laptop if only I had Perfmon and the special plugin :)
Ionizer86 - Tuesday, February 14, 2006 - link
Specs: Thinkpad R50e, Pentium M 1.5 on i855GME.I booted into Windows normal mode as cleanly as possible and ran Perfmon. The CPU was usually in C2 ~60% of the time and C3 ~35% of the time, for a total of ~95% in C2 or C3. Upon plugging in any of my USB stuff (an external hard disk, a Sandisk Cruzer mini, or even my IBM mouse), I'd get 95% in C2 and 0% in C3. Maybe my mouse is a USB 2.0 mouse; not sure.
Battery draw goes from about 11.7W to 12.5W when I plug in my mouse.
By adding the registry key, I no longer have the issue with the Cruzer or my external hard disk, but the problem with the mouse remains.
Looks like MSFT has quite a problem at hand.
Accord99 - Tuesday, February 14, 2006 - link
0.8W, maybe its the power draw of the mouse itself?johnsonx - Monday, February 13, 2006 - link
Adding to what Jason said, you only need the 'secret' plugin for Core Duo processors. The C3 state counter that Perfmon already has works fine on older platforms.IntelUser2000 - Tuesday, February 14, 2006 - link
Not just Core Duo, but: "As you can probably guess, Perfmon is inaccurate in this case. While Perfmon does a fine job of monitoring C3 states for older processors, it fails to handle properly the CPUs we're most interested in: the Pentium M and Core Duo."