dont use USB 2.0 if...

[difenbaker]

... if you're saving on your laptop's batts.


Microsoft driver flaw saps battery strength
By Tom Krazit
Staff Writer, CNET News.com
Published: February 16, 2006, 12:27 PM PST

Microsoft has confirmed the existence of a flaw in its USB 2.0 drivers for Windows XP Service Pack 2 that can cause a notebook to consume power at a faster-than-expected rate when using a peripheral device.

The issue, first uncovered by Tom's Hardware two weeks ago, appears to affect certain Intel-based notebooks running Windows XP Service Pack 2. When a peripheral device was connected to a USB (universal serial bus) 2.0 port, the notebook's battery life plunged at a greater rate than would normally be expected from the use of a peripheral such as a mouse or storage key. At the time that details of the flaw were published, Intel denied its processors or chipsets were the responsible for the issue. And Microsoft refused to confirm to CNET News.com until yesterday that the software company was responsible for the battery performance problem .

Microsoft published a Knowledge Base article on the subject in July 2005, but made that information available only to PC vendors and partners, a company representative said in a statement. The software maker is not releasing the article to the public, but a copy was posted on Slashdot that industry sources have confirmed was the original article.

In that article, Microsoft outlined a problem with its USB 2.0 drivers that prevents a mobile processor from entering advanced sleep states designed to minimize power consumption. On Tom's Hardware's testing, the effect was even more pronounced on Intel's new Core Duo processors, which are capable of entering a deeper sleep state than older Pentium M chips. Other tests by reviewers such as Anandtech found the problem affected notebooks with a variety of Intel processors. It was not clear whether the issue also affected notebooks with Advanced Micro Devices' Turion or Athlon 64 processors.

In the private Knowledge Base article, Microsoft outlined a fix that involved modifying the registry key for USB 2.0. However, since then the company has realized that this is an impractical fix for most users, and is working on a new fix that could involve a BIOS update patch, a company representative said in a statement.

The severity of the problem depends on how USB 2.0 has been implemented in a notebook--which encompasses a wide variety of factors such as the operating system, processor, chipset, USB 2.0 device, and the software and drivers attached to all those components, an Intel representative said. Intel is also working on a fix for the problem that would not be dependent on a software download, such as a tweak to future processors, the representative said.

Notebook users who experience the problem should contact the manufacturer of the notebook for further assistance. Some notebook manufacters have modified the registry keys as outlined in the Knowledge Base article, but this solution does not always work as intended outside of lab testing, the Microsoft representative said.

source:
http://news.com.com/Microsoft+driver+flaw+saps+battery+strength/2100-1012_3-6040586.html?tag=nefd.top


:(

[jayesh]

difen i got to pull u up here on this post... you should have searched more for this... this problem is only specifically currently with dual core laptops such as ASUS A6JA.

it is very well explained in this way from a excerpt from anandtech


" It wasn't too long ago that power consumption was hardly discussed, but these days, you can't have a technical discussion about microprocessors without mentioning it as a design consideration. Mobile CPUs in particular have had to be power-conscious for a pretty long time, thanks to a desire for longer battery life and smaller form factors. But with power consumption, noise and heat dissipation all becoming major issues on the desktop, we are seeing many mobile technologies make their way into desktop CPUs.

The primary goal of a mobile CPU is no different than a desktop CPU, and that is to get its work done as quickly as possible. However, a very important secondary goal of the mobile CPU is to strive to be at the lowest power state possible while getting that work done. The Dothan core used in the 90nm Pentium M processor had a choice of five operating states:

C0 - full power
C1 - auto halt
C2 - stop clock
C3 - sleep
C4 - deep sleep

As you can guess, the higher the C number, the lower the power consumption. Switching between these states is completely seamless to the end user because the switching occurs in a number of CPU clocks (nanoseconds). With each processor generation, the CPU designers attempt, as best as possible, to get the CPU to stay in the lowest C-state more than it could previously. That means making the processor faster so that it can complete its tasks quicker, and thus get to those lower C states faster than before.

With Core Duo, Intel introduced a sixth operating state: deep C4, or a deeper sleep state. Intel made some serious improvements to the core to allow it to not only get to lower C-states more often, but to reduce power even more at these lower C-states. We talked about this briefly in our series of articles on the Core Duo processor, documenting how Intel not only brought forth a dual core mobile processor, but also optimized the performance and power consumption of each individual core.

If you ran any mobile CPU in its full power (C0) state constantly, never allowing it to transition to lower states, you would wreak havoc on your notebook's battery life. While not quite this extreme, the USB 2.0 battery life issue involves a similar concept.

Microsoft describes the USB 2.0 issue as follows:

"Windows XP SP2 installs a USB 2.0 driver that initializes any connected USB device. However, the USB 2.0 driver leaves the asynchronous scheduler component continuously running. This problem causes continuous instances of memory access that prevent the computer from entering the deeper Advanced Configuration and Power Interface (ACPI) processor idle sleep states. These processor idle sleep states are also known as C states. For example, these include the C3 and C4 states. These sleep states are designed, in part, to save battery power. If an otherwise idle portable computer cannot enter or maintain the processor idle sleep states, the computer uses its battery power more quickly than you expect."

Basically, if you have a USB 2.0 device plugged in to a computer running Windows XP SP2, your processor will not be able to enter lower power states (e.g. C3, C4 or Deep C4 in the case of Core Duo). The problem is that if a very power-efficient CPU is prevented from going into its C3 or C4 states, then it's consuming a lot more power than it needs to be. It's particularly bad because the problem could exist just by having any USB 2.0 device plugged in, even if you're not using the device.

Keep in mind that Microsoft's description of the issue does not place the blame on Intel's Core Duo processor, and instead, implies that it would exist on all platforms regardless of CPU. Later on in this article, we'll attempt to find out whether this is indeed a universal problem or something that only really impacts Core Duo.

It is also important to note that the problem appears limited to USB 2.0 devices under Windows XP SP2 and not USB 1.x devices or USB 2.0 devices under other operating systems. There are some USB 2.0 devices that can avoid the problem; in order for a device to be immune to this problem, it must support a power management mode called Selective Suspend, which allows the OS to put the device to sleep until it's needed. The vast majority of devices don't seem to support Selective Suspend, and although some USB hubs apparently do, we weren't able to get our hands on any in time for this article.

[difenbaker]

difen i got to pull u up here on this post... you should have searched more for this... this problem is only specifically currently with dual core laptops such as ASUS A6JA.

mmm... you could be right on that point jayesh, .... but I did not think that it was limited to dual core processors only.


from the article:
"In that article, Microsoft outlined a problem with its USB 2.0 drivers that prevents a mobile processor from entering advanced sleep states designed to minimize power consumption. According to Tom's Hardware's testing, the effect was even more pronounced on Intel's new Core Duo processors, which are capable of entering a deeper sleep state than older Pentium M chips.

Other tests by reviewers such as Anandtech found that the problem affected notebooks with a variety of Intel processors. It was not clear whether the issue also affected notebooks with Advanced Micro Devices' Turion or Athlon 64 processors."



.... so as I understood it, it affects older processors too, but is just not as pronounced or obvious as how it affects dual core procs. As it said...it affects a "variety of intel processors".


cheers!

[Jose_R.A.M]

Hmm...I never run the laptop without the plug being near anyway incase Im stupid and forget to charge.

[jayesh]

hmm we are testing this as i speak even and none of the centrino based procs have yet faced this as a prob...

only the dual core asus have faced this problem ... with our std usb2 hdds /dvd-rw

[666joe]

Freaky eh !!! cheers for the tip