AMD Athlon64 4000+ Underclocking 286
Bios_Hakr writes "PC Stats is running an article on their experiences underclocking an AMD 4000+ processor. Their goal was to try and reduce the voltage requirements and lower the heat output. They benchmark using 3dMark01, 3dMark05, as well as SuperPi. From the article: 'This got us thinking though; what about under-clocking? Most modern processors and motherboards can just as easily run under a rated speed as it can run over... but is there a point to this? Well possibly.'"
Umm.... (Score:1, Informative)
Re:Don't keep us in suspense (Score:4, Informative)
Case fans can generate some audible noise in an environment designed for quiet, and is this really acceptable? Professional studios can acoustically isolate computers, making this a moot point, but home audio enthusiasts don't have this luxury. The question is, how much heat and voltage can be dumped by underclocking a given processor (down) while still retaining acceptable processing performance?
The purpose of this article is to take a very fast, very hot modern processor (in this case an AMD Athlon 64 4000+) and underclock it with an eye to comparing performance to levels of heat and voltage at below stock speeds. The Athlon 64 is currently the fastest available desktop processor, so we reasoned that reducing its speed to the point where it could be operated silently with a passive cooling system should still leave us with a powerful machine for everyday tasks.
been there, done that, it works, no surprises here (Score:2, Informative)
It works perfectly: a drop of 20% in core clockspeed greatly reduced the heat output, the core temperature dropped by almost 10 degrees C.
Re:Don't keep us in suspense (Score:5, Informative)
Re:next article (Score:4, Informative)
Re:next article (Score:3, Informative)
GM trucks now have this (now much-improved) technology, as well as Chrysler's Hemi, as someone else posted earlier.
Use CrystalCPUID to manage speed and voltage (Score:5, Informative)
Of course, in average use, the standard AMD Cool 'n Quiet behavior of running 800MHz at 0.95V while idle will give you battery life that's almost as good as an undervolted setup. 3-4 hours of battery life with a 12 cell battery is common, versus a fraction of that for the poor bastards who bought the P4-based zv5000 series (HP wisely dropped Intel CPUs from their zv6000 line). Undervolting does wonders under heavy CPU load though.
MobileMeter [geocities.co.jp] is my favorite way to monitor CPU speed and temperature, and Hot CPU Tester Pro [7byte.com] verifies that I didn't go too far.
Re:Don't keep us in suspense (Score:3, Informative)
Nitpick: the 90nm 4000+ is a San Diego core. 1MB L2 cache is San Diego, 512MB L2 90nm E3 core is Venice, D-series core is Winchester (older 3000+ to 3500+). (You have to be this geeky to get a 4-digit
I did the same thing you did. I've got a Winchester core 3000+ in my 64-bit Fedora Core server. You can cut power consumption even more with a high efficiency power supply, Seasonic S12's being the absolute best (Newegg carries them). They made a very noticible difference over the Antecs I used to use. Using a 6600GT rather than a 6800GT video card made a huge difference too.
Re:Don't keep us in suspense (Score:3, Informative)
on an AsRock motherboard, yes? I've got two
2600+ systems with identical heatsink/fans.
The one in a MSI KM2M motherboard is rock-solid
stable at full FSB speed (133MHz), but the one
in the AsRock K7VT2 has to be underclocked to
130MHz FSB or else it constantly locks up.
I'm guessing your problem was never cooling,
it was getting stuck with a cheap mobo, as I did.
screw the fans, all i hear is hard drives! (Score:4, Informative)
what I don't see very often is reviews address all the other sounds in a case, like the damn hard drives. I never hear my fans, system is water-cooled with two 120mm fans at 5v, but all nite all i hear is GRINNNNNNNNNNNNNNNNNNNNNND of the damn hard drives. Why doesn't someone address this issue and do a REAL review on how to get rid of hard drive sounds? Sure silentpc has done a few, but everyone else is like "yeah, i hear like, a fan, sometimes, so i'm gonna run my new 4000+ processor at 800mhz".
talk about unoriginal....
Re:Low-power computer with commodity parts (Score:3, Informative)
Unfortunately, the article does not give any numbers on the actual power consumption or ambient temperature, so we have to look elswhere:
LostCircuits http://www.lostcircuits.com/cpu/amd_venice/ [lostcircuits.com] has some actual measurements of CPU power usage.
The guys found out that the Venice/3800+ uses less than half the power of the Clawhammer/4000+. The actual clock frequency is the same for both processors, 2.4GHz.
To top it off, they found that the 3800+ showed slightly better overall performance than the 4000+. It seems that the detail improvements that went into the Venice core do more than compensate the Venice's smaller cache.
Re:Faulty Analysis? (Score:2, Informative)
For CPUs, a better model is P = C*V^2*F (capacitance times voltage squared times frequency). If you halve the voltage and halve the frequency, the [dynamic] power drops by a factor of 8. Unfortunately, modern transisots leak, so you probably won't actually see that much drop, but the point is, underclocking even a little can result in huge power savings.
The real results (temp increase vs absolute temp) (Score:5, Informative)
--
The article states:
Unless the computer and participants were in a frozen room (at 0 degrees celcius), their analogy is flawed. The amount of heat generated is directly preportional to the temperature INCREASE above the ambient temperature. Let's assume that the test occurred at "room temperature" (70F deg or 21C deg). The chart would look more like the one below:The article should have stated:
"For a 66% drop in speed, there was a 53% drop in added temperature."
"a 43% drop in voltage produced a 53% drop in in heat seems more reasonable."
My observation from that data above:
"A drop of only 400MHz (17%) and 0.15V (11%) showed a significant drop in the amount of heat generated (25%)."
Re:Their Maths is a little suspect in places (Score:3, Informative)
The reason being that if 20C is the ambient temperature, then 20C is the absolute coldest we could expect to achieve using forced air cooling. If the chip is at 20C (zero on this scale) then the cooling is perfect.
Choosing absolute zero is appropriate at times of course, like when trying to figure out how much kinetic energy something has.
Re:Use CrystalCPUID to manage speed and voltage (Score:4, Informative)
While over there don't miss Bryan Cassell's excellent article [silentpcreview.com] comparing the Athlon to Pentiums for 'quiet power'. He points out that Intel's TDP numbers are not maximums, but that AMD's numbers are. A very interesting read.
I am quite surprised that no one has leaked a copy of AMD's own PSTcheck as mentioned in this article [tomshardware.com]. I have searched for it but to no avail. I would love to be able to play around with that one.
Re:This is getting off topic, but... (Score:1, Informative)
This is, at best, a gross inaccuracy.
Stoichiometric only exists to help the catalytic converter run at optimum efficiency. Stoichiometric also aids in reducing emissions. In actual racing applications, where neither is a concern, you can see A/F mixtures as lean as 17:1, sometimes more (depending on materials used). Maximum power with 12:1? That's bullshit. I've built and dyno-tested countless engines (it's what I do to eat) and, across the entire RPM range, both Torque and HP increased with leaner A/F Mixtures than with richer (15:1 is a good start, but each engine must be specifically built/tuned for it's application). 12:1 is way too rich. I have dyno sheets to back all this up, and they all include A/F readings.