Dr. John v. Kampen

Hot tips for warm Linux holidays...

Sunday, July 31, 2011 4:53:33 AM

users, BIOS, Ubuntu, Mint, clockspeed, Linhx, tips, kernel, over-heating

Frying your eggs on a laptop or netbook, or whatever small computers are called today, may be a hidden feature for some. Many however already discovered that these small computers can get hot, in fact too hot. Medical journals warn men for using laptops in places where they are meant to sit and work. It could impair fertility. Only read about burned thighs of some ladies. I came upon this reading about computer cooling. Why I did? Because I suddenly suffered from heating problems on my Mint 11 Linux box, a common desktop PC said to have excellent ventilation. True, these weeks the outside temperatures run pretty constant into the 100F/38C category, whereby my office can't produce temperatures lower than 88F/31C. All above the manufacturer's specifications for my Gigabyte GA-P55UD5 that set the limit to 84F/29C. But there was more at play - possibly an unnoticed Linux kernel regression, a persistent quirk in Ubuntu/Mint and an oversight on my part. The heat was on to discover what went wrong and what can be done to counter some problems...

Url movie: http://youtu.be/BPX6YLJMl58

Heat may damage your computer. It doesn't matter whether it is a desktop box, a laptop beauty, a netbook baby or some other electronic gadget. The question what temperature is considered Tmax for a CPU remains for most users unanswered. Specifications are often vague or failing in computer reviews. Manufacturers sometimes offer confusing tables with data about temperatures and clock-speeds for certain chip-families. For my Gigabyte P55 I found that a CPU temperature above 140F/60C was the red line for performance when overclocking. Intel allows Tmax. 72.9C/163.3F for my i5 chip. The CPU would start throttling down when getting a full load of instructions just below that value. The reverse from what I wanted. My aim was running 3.6 Ghz at about 112F/45C. Fast enough for me anyway. From January until yesterday this performed well, running Linux Mint LMDE and Mint 10, the latter recently changed for Mint 11 Katya. With that change and using Mint 11 as primary OS some peculiar anomalies started to occur. Temperatures started to fluctuate between 44 and 60 Celcius (111 to 140F). I suddenly heard the ventilators of my always very silent box. GKrellm software to check system functions revealed unexplainable temperature wobbles and higher fan speeds. The System Monitor add-on however appeared not to show any recognisable culprit apart from Nautilus, that still consumes many resources and power at start-up when discovering a lot of files on the hard drive. Changing some Preferences (in the 'Preview' part) made a difference. 'Preview' now leaves out previews of Music files and only goes after some Local Files. Aside from that here I found a solution for another contributor that doesn't leave where others leave off: appmenu-gtk. This module keeps hanging around and consumes ever more memory. To remove it do:

sudo apt-get remove appmenu-gtk

Heat may also result from power-consumption. In that respect it surfaced that Ubuntu 11.04/Mint 11 are less conservative. Tests by Phoronix show that these Linux versions are less favourable for certain configurations, consuming up to 33% more energy than otherwise, but not returning more speed. Digging even deeper at the Phoronix website I found this article as a warning for mobile users. But Mint 11 runs with Linux kernel 2.6.39 and not the mentionned 40, which suffers from a regression. It then came to me, that an old memory management quirk could be at play. I wrote about that already. Yet, by applying the following code in the Terminal:

 echo 3 | sudo tee /proc/sys/vm/drop_caches

I noticed a drop in temperatures of at least 5 degrees in a minute. Flushing the caches appeared to be involved for some reason. That issue seems to be controversial in the Linux geek communities. Anyway it made me patch /etc/sysctl.conf in the File System. I added these few lines there after making a backup of the original:

 vm.swappiness=33
 vm.dirty_background_ratio = 4
 vm.dirty_ratio = 8
 vm.dirty_expire_centiseconds=1500

Nevertheless I kept the flush instruction above at hand and the System Monitor panel add-on displaying memory usage only to see if some application(s) kept hanging around or filling RAM-memory. That way I found that a full memory shown in this panel add-on lead to slower, less 'agile', performance and elevated temperatures. Running from RAM is advertised as 'much faster' and safer, but I can't agree. It's the theory, I assume. Fact was, that OpenShot Video Editor (video editor), Audacity (sound editor) and K3b, KDE's excellent CD/DVD burner also working well on Gnome footprints, had a tendency to use all memory and impair system stability and agility (responsiveness) visibly. Flushing caches transported this problem to the fast hard drive, but improved power consumption and agility of my system markedly. Whether this is a 64-bit quirk I don't know.

However this wasn't all. Cleaning the box from dust (and dog's hair, we have 7 regularly visiting my office to keep me company) now and then is necessary. You would be surprised what can be found on fans and even at air openings of your computer. So, brush and duster had to be used to attack that enemy. The sticky sandlike dust from our Andalucian desert sometimes drives me mad, requiring an inspection every 4 weeks or so depending the direction of winds. For that reason the supplier of my computer taught me the 'trick' to open the box myself without invalidating warranty. His warning sticker is over the sides I must open and I would break it if removing a side-panel to access it. Just carefully push a tiny screwdriver or paper-clip under the sticker and 'roll it off' very slowly. It will stay intact and can be used again after closing the case. In a way I felt like a thief doing that, but the service department of the supplier was glad not having to regularly venture into our desert, far away from civilisation, for something 'any fool can do by him/herself'. Inside I discovered 2 anomalies. Apparently the active heatsink with fan that sits upon the Intel CPU had detached itself. And the 'chimney', yes a tube, from the heat-sink to the outside was displaced. I had my computer designed that way to cope with 'out-of-spec' summer-heat. The latter aspect was my oversight to position the 'chimney' back in place, whereas the first simply required cleaning the surfaces from both CPU and heat-sink to apply some new thermal compound (in a thin layer) to 'glue' them together again. Laptops and netbooks may have a copper strip across CPU and other vital parts to get rid of heat, blown out at the bottom (causing these burned thighs). That's why many use some extra cooling underneath. Having solved these aspects my P55 runs clean again at normal temperatures for the time of year. Listen to your fans or watch your OS's agility to see if cleaning is required - software and hardware I mean.