Athlon 64 power reduction: C'n'Q, Vcore, mobile, tools 1. Cool'n'Quiet 2. Beyond Cool'n'Quiet 3. Mobile Cores 4. BIOS undervolting 5. Software for changing multiplier/voltage/FSB 6. Interesting threads
I believe this information could be very useful for Athlon users. I will update this list when I encounter new information.
This thread is replacing the old one
in the "Silent Front" forum.1. Cool'n'Quiet What, Which, How?
Cool'n'Quiet varies the frequency and the voltage of the CPU depending on the actual load.
It reduces the power in 2 ways:
1. It reduces the leakage power at idle. The Athlon 64 puts itself to sleep when the HLT/STPGNT instruction is sent. At this stage, only the leakage power is drawn. By reducing the voltage and frequency, this power is cut down significantly.
2. It reduces the power needed during light and medium load. When the CPU is able to cope the work at a low frequency/voltage level it stays at this level.
The perfomance penalty if this solution is negligible.
All Athlon 64 and all A64-based Semprons >=1,8Ghz
support this feature. The registered memory used by the socket 940 CPUs Athlon 64 FX (old) and Opteron does prevent this feature. The new upcoming E3 revision Opterons have Optimized Power Management (OPM) which is the same technique. Apparently, the mainboard has to be compatible.
According to AMDZone
, you may experience performance loss using dual-core AMD processors with Cool'n'Quiet enabled on Windows XP SP2. Microsoft is reporting
the problem in a knowledge base article, but doesn't let you download a hotfix, you need to contact them directly to get it...
However, a patch
is available from AMDZone, which improves CPU performances and addresses some Cool'n'Quiet issues.
Please read the instructions carefully if you decide to apply this patch, since you need to change registry settings also. That patch seems to be a beta one, and this is probably why microsoft is asking you to call. Use it only if you experience instability or performance loss, or if Cool'n'Quiet is not working correctly. A restore point should be made before applying the patch, just in case... (text
There are known problems
with socket-754 boards and 2+ DIMMS. You can find compatibility notes on some boards in the recommended lists. You can also ask in the forum if someone has a stable operation with 2 DIMMs. According to Aopen, 3 DIMM socket-754 configurations are incompatible with Cool'n'Quiet.
When you are choosing an Athlon 64 now, go for the 90nm cores:
Socket-754: "Palermo" (Rev D0) Semprons (which are made out of a cache-halved "Oakville" core) with a TDP of 62W available at the moment. The OPN ends with -BA.
"Palermo" (Rev E3) Semprons are available too. TDP: unknown. The OPN ends with -BO.
Socket-939: There is the "Winchester" (Rev D0) core available. The TDP is 67W and the OPN ends with -BI.
"Venice" cores (Rev E3) are available too. TDP: 67-89W. The OPN ends with -BP. The Venice core is said to consume a tad less power then the Winchester. Sources 1 2
Cache-doubled "San Diego" (Rev E4) are available too. TDP: 89W. The OPN ends with -BN.
If you can't get a 90nm core, get a least a core with the CG-stepping
Examples of the benefits:Computerbase
got 7W AC drop with a 2800+ (socket-754), 17W AC drop with a 3400+ (socket-754) and 22W AC with a FX-53 (socket-939).hardwareluxx.de
examined socket 939 CPUs and got 23W AC drop for a 3500+ and 35W for a 3500+.hardtecs4u.de
shows 8W DC drop for a 3500+ 90nm Winchester.
The faster your CPU, the more important Cool'n'Quiet gets. All Athlon 64 of the same stepping seem to have the same practical Cool'n'Quiet idle power regardless of their frequency.
Installation instructions here
. You can download a dashboard
from the AMD site in order to check the correct function.
Athlon 64 drivers here
Athlon 64 X2 drivers here
Opteron drivers here
has a hudge german thread about Cool'n'Quiet problems. Common symptoms are: instant crash after activation, crash after some hours, problems with Windows starting.
The following fixes solved some problems:
- do an image of your system partition. Sometimes a malfunctioning Cool'n'Quiet demolished Windows installations.
- get the newest production BIOS. If it doesn't help, get a Beta-Bios.
- install the newest driver from AMD.
- the RAM is quite cruical. If you have a socket-754 board try only one stick. Lower the timings and/or the frequency.
- shift around the RAM sticks.
- Win XP Service Pack 2 seems to make problems.
- try RMClock since it apparently alters the frequency more softly. Mainboards supporting Cool'n'Quiet
AMD has a list of recommended mainboards
. Click on mainboard to see if it AMD validated Cool'n'Quiet on this board.
Some manufacturers (at the moment: Asus, Epox, MSI, Abit-usa) list Cool'n'Quiet compatibility on their specification sites of their products.2. Beyond Cool'n'Quiet Tweaking of the P-States
Cool'n'Quiet sets the speed and the voltage to defined levels (P-States). It does not work together with any custom BIOS-voltage or multipler/voltage changing tool. The power user may want to tweak this. For example:
- You want to save even more power by setting the Vcore to the lowest possible level for each state.
- You don't need the maximum power of your CPU (e.g. small server, HTPC) and lower the maximum state.
If you want to play around with the multiplier, you probably have to enable Cool'n'Quiet in the BIOS nevertheless.
Two tools are available for this task:RMClock
. Information about the differences of these two utilities can be found in the SPCR-Forum
is able to adjust your reference clock (aka FSB) via keyboard shortcuts.Mainboard does not support Cool'n'Quiet
You are not lost. Your energy hunger is still comparable to a Intel Prescott with C1E or EIST since the Athlon 64 still has disconnect on HLT/STPGNT enabled. Here, the CPU basically goes down to a very low frequency (4-250Mhz) while it recieves the HLT or STPGNT instruction. The voltage stays the same, though.
Note: When Cool'n'Quiet is enabled, the disconnect feature is still active.
There is the possibility to underclock your Athlon 64 by adjusting the reference clock (aka FSB). This may be handy in order to limit the heat output when the cpu is busy. There shouldn't be any effect on the idle temperature.
Dynamic underclocking via the reference clock (aka FSB) is not supported by any software afaik.Clockgen
is able to adjust your reference clock (aka FSB) via keyboard shortcuts.3. Mobile Cores
There is a comprehensive post
in the anandtech.com forum.
Mobile cores don't support Cool'n'Quiet out of the box. I suspect that RMClock and CrystalCPUID are still able to set the P-States dynamically. Even Windows XP might be able to access the power profiles - please report in the forum about this.
The current situation in terms of low-power is as follows:
04/2005: There is a 90nm socket-754 mobile version called "Oakville" existing. It has 1,35V, which is not a big step compared to the 1,35/1,4V of the "Venice". Since it is extremely difficult to find a motherboard supporting mobile and 90nm, just get a desktop 90nm. 4. BIOS undervolting
You may have noticed some discrepancies in the recommended Cool'n'Quiet list
and the recommended undervoltable list
. In theory, every mainboard supporting Cool'n'Quiet should be able to undervolt. But manufacturers often don't include the voltage adjustments in the BIOS.
You may want to have BIOS voltage adjustments when you want to use Linux or when you fear that the booting of you PC may cause you CPU to overheat with the current cooling.
Once you are in Windows, you should be able to adjust the Vcore with the usual utilities including the ones supplied by the manufacturers. CrystalCPUID
are providing a command-line interface. If there are any exceptions from this rule, please report. 5. Software for changing multiplier/voltage/FSB
This tool allows user adjustable Cool'n'Quiet voltage/frequency settings.
This tool allows user adjustable Cool'n'Quiet voltage/frequency settings. You need a Athlon64 or mobile/modded XP.
His software CpuMsr is able to change many settings of you CPU. For example, you can adjust the divisor of the S2K disconnect feature as well as the clock change speed.
Multiplier/voltage/FSB adjustments by keyboard shortcut.
Powerful replacement for the Windows XP built-in energy control.http://www.cpufsb.de
Supporting many mainboards and CPUs.
IMHO the best temperature logging utility.
Btw, interested in better fan speed algorithm
Supports changing the FSB on the fly. It is no longer in development. 6. Interesting threads
DFI nForce 4 boards allow overvolting while sticking to AMD Cool'n'Quiet driver. Link
8th apr - added OPM
22th oct - added X2 compatibility
Suggestions are very welcome.