Linux and the Desktop Pentium M: Uncommon Performance
by Kristopher Kubicki on December 24, 2004 12:00 PM EST- Posted in
- Linux
A bit about Speed Step, Thermals, Power and Noise
Although this is not the first time that we have looked at Dothan, the exciting bit about the technology is that it requires so little power and thus, so little cooling. The only active cooling required in our Pentium M setup was a 40mm fan on the processor heatsink; the Northbridge is cooled passively.
Click to enlarge.
Another reason why we selected the DFI motherboard for this roundup was the fact that it uses such elegant cooling. The HSF combo is proprietary to this motherboard, but it will fit easily in a 1U or SFF case with plenty of clearance and low noise. When we had our test rig setup in an aluminum Hornet Pro SFF chassis from Monarch Computers, we only needed a single, low RPM 80mm fan and the 40mm CPU HSF to cool the rig. At full operation, the Dothan desktop system ran at less than 30 dBA, too low for our Extech devices to even get a measurement at 12".
Click to enlarge.
After a full hour of operation, our BIOS reported the Dothan at a "cool" 98 degrees Fahrenheit. The 40mm fan above is clearly ample enough for our purposes, but we did a little overclocking up to 2.4GHz and the same HSF combo held up fine. More importantly, the combo came free with the motherboard. What interests us even more is that this configuration is not even running Enhanced Speed Step! The 2.6 Linux kernel provides us with an excellent method of adjusting the CPU clock, dubbed "CPU Frequency Scaling". Unfortunately, this option is not enabled by default in most kernel configurations and requires a recompile.
In the .config file of a 2.6.x kernel build directory, we have to change the following lines:
CONFIG_X86_ACPI_CPUFREQ=y CONFIG_CPU_FREQ_GOV_USERSPACE=yBoth lines should now read "y" for yes. After restarting the computer, setting the processor clock speed is as easy as this:
echo 600000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeedThe sys daemons now will read the scaling file and dynamically clock the processor to 600,000 KHz. Although this amount of control is great for us right now, running a real time daemon to monitor CPU usage would probably be a little more beneficial to us. "cpufreqd" and "speedfreqd" both take control of the CPU scaling and work the same, if not arguably better than the Windows driver that does the same thing. For the tests in this analysis, both daemons were disabled; although, if you plan on getting the most out of your laptop or Dothan desktop, you should run a daemon for the best thermals and power usage.
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bhtooefr - Saturday, December 25, 2004 - link
Problems on the John the Ripper section:DES: Where's the 755?
MD5: Where's the 400MHz FSB 765?
Blowfish: Where's the 533MHz FSB 765?
Also, for anyone who wants to know what the heatsink IS, x86-Secret reviewed this before the heatsink was available, and they used a MicroCool northbridge heatsink.
FWIW, I don't know why nobody's coupled this thing to an i865/875. It's definitely possible, as Shelton (0K L2 Banias) has been coupled to an i845, and Banias has been coupled to an E7501. And, the fact that Alviso is "i915GL" says a lot. Mobo makers should be able to simply rework the traces leading to the socket, and reuse their P4 board designs for a P-M board design. Or, if they're REALLY lazy, they could just make an adaptor - put the processor in it, and drop it in the socket.
ImSoHighRightNow - Saturday, December 25, 2004 - link
"Encode rate, more are better"? Some encoding rates can't be "more" than other encoding rates. They can be HIGHER, but not "more". I would suggest "Encoding rates, higher is better"You know what you need? A grammar handbook. Nothing annoys me more than someone who can't conjugate "to be" correctly. I learn conjugations for other languages, the least you can do is learn conjugations for one verb in English. Thanks
ImSoHighRightNow - Saturday, December 25, 2004 - link
"Rendering time in seconds, less are better"Shouldn't that read more like "Rendering time in seconds, fewer is better" or "Rendering time, a shorter amount of time is better"? At least something remotely grammatical would be preferable. Thanks
miketheidiot - Saturday, December 25, 2004 - link
dothan will need work before its ready for desktop. Simple as that. And make it cheaper two, that would be good. $500 + $250 for a mobo is quite a bit, even if it does OC well.DrMrLordX - Friday, December 24, 2004 - link
Looks like the Dothan falls flattest when it's faced with multiple concurrent threads. Dual-core Dothan solutions might alleviate some of that problem, but, perhaps this is one of the reasons why Intel has been rather shy about pushing multi-core Pentium Ms for the desktop?Googer - Friday, December 24, 2004 - link
It seemed to me that the extra performance 133mhz that the 533 bus provides is rather small. My suggestion is couple this with an 875 or 865 chipset @400mhz and let dual channel memory add the needed performance boost. Its probably the cheapest and most effective way to increase the performance of Pentium M.Pannenkoek - Friday, December 24, 2004 - link
I believe that the price of the processor tested should have a more prominent position in the whole test. It's, after all, about the price/performance ratio for most of the consumers.If you plan on testing GCC vs ICC then I recommend to visit http://www.coyotegulch.com (though the site is "temporarily unavailable"), where you can find comparisons between the compilers, compile settings and more.
The focus of the tests on the site is on scientific applications/algorythms which fit in cache, and is therefore more about how many micro-optimizations are not missed. Which explains why results can vary so much; and also why the ICC compiler, made by Intel for Intel processors, can be sometimes a lot faster than GCC, which does not share the intimate knowledge of the inner working of those processors and targets a zillion other architectures as well...
sprockkets - Friday, December 24, 2004 - link
I wish though you included pics of the fully assembled system. I would like to see that HSF, since it appears AOpen simply uses a 478 type heatsink bracket. But looking at the board at newegg.com, the Aopen board comes with the heatsink, and has DUAL Marvell Gbe, plus it has a SATA controller on it as well, and costs $14 less.MDme - Friday, December 24, 2004 - link
Anand and co: when will you guys do a full review of this chip against P4 and A64 across the different applications, games, etc? that would be a great gift to your readers at AT.JustAnAverageGuy - Friday, December 24, 2004 - link
Page 6:"We also took the same POV-Ray benchmark and ran it against the Pentium M clocked at speeds from 1.0GHz to 2.4GHz."
Should read 1.6GHz
[shake 3.5c]"Although it holds up well against an Athlon 64 3200+"
Doesn't seem like it. It took over 12 minutes longer.