Archive for June, 2007

Linux on a Acer Aspire 3680

Acer Aspire 3680 is a budget laptop using the Celeron M processor.

Fedora 7

The 32-bit and 64-bit version of Fedora 7 will work on this machine because Celeron M 520 is a 64-bit processor. Most things will work right out of the box. The only exceptions are:

  • Sound works, but defaults to mute. You must un-mute the controls.
  • The multimedia card slot does not work.
  • Wireless is an Atheros based card and require you to download restricted drivers.

Enabling Sound

The sound driver works, but you cannot hear it because the playback device is set to mute. The playback device is actually “Surround”.

  1. Double-click on the speaker icon in the title bar. This brings up the volume control.
  2. Click on edit preference. This brings up a list of volume control preference.
  3. Check the box for “Surround” and press Close.
  4. A surround control should appear in the volume control. Unmute the surround control and adjust the volume.
  5. Close the volume control.
  6. Right-click on the volume control again and select Preference. This brings up a different volume control preference. This allow you to select which control the main slider is hooked to.
  7. In the Volume control preferences. Select Surround and press the Close button. This connects the volume slider to the surround control.

Unfortunately, all of the other controls on some of the media software like RealPlayer is hooked to the wrong control. Changing the volume control does not change the surround and so you must use the volume control on the menu bar instead of on the media player.

Enabling the Restricted Repository

Unlike Ubuntu, Fedora does not include any restricted codec or drivers, to get those drivers, you need to add the restricted repository.

  1. Log into Fedora as root.
  2. Open a terminal by selecting the menu Applications->System Tools->Terminal.
  3. Type in the following statement:rpm -Uvh
    rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-livna
    The U parameter tells the rpm to upgrade the package by removing the old package and installing the new one. Because U works even when there is no previous package, you should use “U” instead of “i”, which just installs. The “v” is verbose output and “h” is used with the “v” to print the hash marks. The second line imports the public key for Livna used to check that the packages come from Livna.


The wireless chip in Acer Aspire 3680 is Atheros based, but the exact model will vary from machine to machine. The first Acer 3680 I purchased had an Atheros AR5006EG chipset. When that laptop failed and had to be return 2 days later, the new Acer had an Atheros AR5005G.

  1. You must enable the livna repository. See instructions on how to do this earlier in the blog.
  2. Login as root.
  3. Open a terminal window and type the command:
    yum install madwifi
  4. Select the menu System->Administration->Services. This brings up the service configuration.
  5. Check the checkbox for NetworkManager. You’ll need this applet to switch between different wireless networks.
  6. Close the window. Press Yes when asked to save changes.
  7. Reboot machine. You should see an applet icon on after startup.

Note that I had trouble with getting the madwifi driver working with AR5006G and AR5005EG chipset under 64-bit. I was able to get AR5006G to work fine under 32-bit Fedora 7.

June 25, 2007 at 8:36 pm 27 comments

Does On-Demand Clock Modulation (ODCM) conserve battery?

Many low price laptop these days come with Intel Celeron M. Unlike its competitor, the AMD Mobile Sempron, Celeron M lacks dynamic frequency and voltage management. On processors like Mobile Sempron, Pentium M, Core Duo, and Core 2 Duo, the cpu drops frequency and voltage when there is less work load. So if nothing is going on, your cpu may drop from 1.8 Ghz to just 600 mhz and voltage may drop from 1.2v to 1.0v.

Celeron M in contrast runs at the same frequency and voltage all the time. This is why Celeron M typically have a shorter battery life than their mainstream cousins. Celeron M does have On-Demand Clock Modulation (ODCM). Can this be use to increase battery life?

How does ODCM work?

ODCM conjured up an image of a cpu dynamically changing the clock of the cpu depending on load. In fact, all ODCM does is force a processor to go into idle. Suppose you set the ODCM throttling to 75%. Your processor will work normally 75% of the time, and spend the other 25% slacking off. As a result, your cpu runs at the same clock speed and voltage, but runs slower because the cpu is forced to idle.

Does this actually save you power? Well, that depends on your usage. Suppose your cpu is running always at 100%, you are going to use a lot of power. Suppose you then set ODCM to throttle at 50%. 50% of the cycle will be idle, so you will use less power because the computer is at rest 50% of the time. However, the task will now take twice as long, this is not a good trade off.

If on the other hand, you’re going to do is type something in the computer, then your computer is probably idling most of the time waiting for you to press a key. In that case, power usage with ODCM and with ODCM is probably not all that different in both cases the computer is in idle most of the time. However, what if the forced idle uses less power than the natural idle state. Basically if you were to sit around and your computer goes into idle, does it use more power than if ODCM force the computer to idle? I decided to test this out.

The Test

The test platform consists of a Acer Aspire 3680 with a Celeron M 520 1.6 Ghz, 512 Mb RAM, and standard battery. I will run two trials.

  1. Normal Test – Laptop is turned on and left alone until the computer powers off.
  2. ODCM Test – Run RMClock and set it to throttle at 12.5%. Leave computer alone until the computer powers off. This causes the computer to go into force idle 87.5% of the time.

In both cases, we set the power manager to not turn off the monitor or hard disk. We also make sure nothing is schedule to run during the test. Wireless is turned off.

In both case, the computer powered off at about 2 hours. This mean that the forced idle uses the same amount of power as the normal idle. There was no power savings at all.


ODCM is not a useful tool for battery conservation. Most mobile processor conserve power by idling at a lower clock speed and voltage. ODCM is a poor substitute that attempts to force a processors to go into idle mode. However, since the force idle mode uses exactly the same power as the normal idle mode, you will not notice any power savings.

June 23, 2007 at 8:19 am 9 comments

Device driver incompatibility – the painful part of Linux

Recently, my main laptop died and had to be send back for repair for the second time. I decided to get a backup laptop so I can continue to work on stuff while the main laptop was being repair. The Linux Tech Show and the Linux on the Desktop folks recommended the cheap laptop Acer Aspire 3680. The host indicated that he tried multiple distro on it and they all work.

Unfortunately, things did not go smoothly. Sound didn’t seemed to work. The wireless did not work at all. The problem is that not every Acer Aspire 3680 have the same components. Many have different versions of the Atheros chip. Some versions are compatible with Linux, some are not. I tried to download the lastest MadWifi and then tried to use NDISWRAPPER. Nothing worked. The chipset in my laptop, Athero 5006EG is not compatible with MadWifi or NDISWrapper. To make things worse, there may be different versions of Athero 5006EG, since some people managed to get theirs to work.

In addition to the wireless, the SD Card reader did not work because the TI drivers are broken. The sound was actually working after all. It turns out that the sound defaults to mute, so it gave the appearance that it was not working.

This is what drives me nuts about Linux at times. Of course, this problem affects Windows, too. The difference is that Windows are often preloaded, so you generally do not encounter this sort of problem.

June 15, 2007 at 9:35 pm Leave a comment


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