I read online that underclocking is often tried to reduce or eliminate fan noise, reduce power consumption, and/or minimize the buildup of heat, but is it really worth the effort?
It is rumored that the energy efficient Phenom family of processors are actually just underclocked Phenom processors. Therefore, it may be better just to underclock a regular Phenom processor.
Underclocking tests have been done on many AMD and Intel processors with varying results. Underclocking seems to provide the following benefits improving as the speed is decreased:
- Less power consumption = save money on electricity bill
- Less heat dissipation = Possible to run computer without CPU, motherboard, or any other fans
- Computer may last longer than a computer that is not underclocked.
Underclocking also provides the following disadvantages:
- Computer takes longer to do various tasks
- Computer may become unstable if underclocking settings are not correct
Therefore, underclocking a CPU can be a viable option if one knows how to do it. Furthermore, underclocking can be an effective way to save money on one’s electricity bill. Depending on who you bought the computer from, the option to overclock and/or underclock maybe locked. Dell and HP often lock their BIOS.
For the AMD Phenom II processors, the CPU can be underclocked easily. Looking at the screenshot below for a Gigabyte motherboard, one will notice that everything is set to auto. If you want to underclock the CPU, one has to change the CPU Clock Ratio from auto to manual and pick a number to multiply by. The calculation is CPU Frequency (MHz) X CPU Clock Ratio. Therefore, if one wants to underclock to 2000MHz(2GHz), the CPU Clock Ratio must be changed to 10X. 200MHz X 10 = 2GHz CPU.
The same can be done for the CPU NorthBridge Freq. and the HT Link Frequency. If one wants to underclock to 1000MHz(1GHz), then the CPU NorthBridge Freq. and the HT Link Frequency will both be set to 5X. The calculation is CPU NorthBridge Freq. (MHz) X CPU Frequency(MHz). Which will be 5 X 200MHz = 1000MHz. The HT Link Frequency must be less than or equal to the NorthBridge Freq. otherwise Windows may not work.
The SouthBridge, oddly enough, does not have any underclocking or overclocking settings. There is a reason for this. All the devices connected to the SouthBridge are “slow” devices. Although, there probably is motherboards out there that will allow one to overclock or underclock the SouthBridge. Nevertheless, the SouthBridge does not seem to have any heat and/or performance issues. Therefore, changing the SouthBridge speed maybe pointless.
Taken from Gigabyte’s GA-MA790FXT-UD5P motherboard manual. Used to simplify the understanding of how the motherboard works.
The AMD 790FX is the North Bridge and the AMD SB750 is the South Bridge.
NOTE: Apparently, it seems that the Northbridge is supposed to be the one transferring data to and from the RAM. Therefore, it is quite possible that the diagram showing the CPU transferring data to and from the RAM shown below by Gigabyte is wrong. The article can be seen at http://en.wikipedia.org/wiki/Northbridge_%28computing%29. Although, it could also be that Gigabyte built their motherboards that way.
Underclocking seems to provide the most benefits when the computer is running at full speed. Since the CPU and/or the North Bridge are running at a slower maximum speed, the temperatures will also be lower. This will allow the fan to spin slower and produce less noise. An option that may appeal to silent computer enthusiasts.
It should be known that the power supply only draws enough power to run the computer. Therefore, a 600W power supply will not provide 600W of continuous power. It can and will provide 200W of continuous power if that is what the computer needs.
In conclusion, I believe that if one really wants to save money on electricity bills, buy an energy efficient power supply and build one’s computer to maximize the airflow in and out of the case. If the inside of the computer can be kept cool, it will use less energy trying to cool the various components. Furthermore, only install what you need. For parts that are used once in a while, buy an external version. That way the device is not drawing power while in standby inside your computer and unplug it when not in use.
I believe in the saying that you get what you pay for. Buy a cheap computer, and you will pay more in other ways. Buy a decent computer, and it may be worth the price. Unfortunately, to buy a decent computer, you should know what parts to buy. Not all parts are created equal.
Underclocking from the Wikipedia. http://en.wikipedia.org/wiki/Underclocking.
Underclocking a 1GHz CPU. Written in 2002. http://www.silentpcreview.com/article37-page1.html
Underclocking an AMD Athlon64 4000+ CPU. Written in 2005. http://www.pcstats.com/articleview.cfm?articleID=1798
Comparison of the AMD Phenom X4 energy efficient and regular CPU’s. http://www.bit-tech.net/hardware/cpus/2008/07/24/amd-phenom-x4-9350e/1
Overclocking terminology and learning how to overclock. Once you learn this, underclocking should be easy. http://www.ocia.net/articles/k10overclock/page1.shtml
In addition, Windows 7 and Vista have the ability to control the CPU. This will explain why my CPU is running at about 1/4 of maximum speed during idle times. Therefore, if your BIOS is locked and/or you want to try the Windows 7 or Vista method, http://www.vistax64.com/overclocking-cooling/238678-help-underclocking-plz.html may help. Unfortunately, it seems that the maximum does nothing. I set the maximum at 50%, but the CPU still runs at 100%. Therefore, that functionality is not working as of November 11, 2009.
Actually your CPU controls your CPU. Modern CPUs decrease their speed when they’re not under load.
Thank you, revan05. The link to the AMD Overdrive OC manual can be found at http://game.amd.com/us-en/drivers_overdrive.aspx. Furthermore, the Memory controller, http://en.wikipedia.org/wiki/Memory_controller, is new to me. It seems that AMD and Intel are moving towards putting whatever they can onto the CPU chip. Therefore, revan05 is correct. The newer CPU’s have a Northbridge built into the CPU to remove the delay in communication between the CPU and the RAM.
I think that in the gigabyte manual they mean the northbridge on the cpu transfers mem data, not the nb(790fx) on the motherboard. This is a frequently used misconception regarding the term “northbridge”, as one learns from reading the AMD Overdrive OC manual.