Sign in with
Sign up | Sign in

Terminology

How To: Overclocking Your AMD Processor
By

Multiple terms used to describe the same thing can confuse or even intimidate a computer user from grasping the fundamentals of overclocking. So, before we move on to the how-to part of this article, it’s a good idea to cover some of the various terminology associated with overclocking.

Speeds, Frequencies, Clocks

Core Speed (CPU Speed, CPU Frequency, CPU Clock Frequency, CPU Clock Speed): The frequency at which the CPU executes instructions (eg.: 3,000 MHz or 3.0 GHz). This is the main frequency we hope to raise out of all the other different components.

HyperTransport Link Speed: The frequency of the link between the CPU and the northbridge (eg.: 1,000 MHz, 1,800 MHz, or 2,000 MHz) This is usually equal to (but must not exceed) the northbridge speed.

Northbridge Speed: The frequency of the northbridge (e.g.: 1,800 MHz or  2,000 MHz). For AM2+ processors, increasing the northbridge speed will boost memory controller performance and L3 cache speed. This must not be lower than the HyperTransport link speed, but it can be raised much higher.

Memory Frequency (DRAM Frequency and memory speed): The speed, measured in megahertz (MHz), at which the memory bus operates. This can be represented by the actual frequency, such as 200 MHz, 333 MHz, 400 MHz, and 533 MHz or the effective speed, such as DDR2-400, DDR2-667, DDR2-800, or DDR2-1066. 

Reference Clock: By default, this is set at 200 MHz. As you will see for AM2+ processors, other frequencies are based on this clock speed and are calculated with multipliers and sometimes dividers. 

Calculating the Frequencies:

Before moving on to our description of how these frequencies are calculated, we need to mention that most of this guide covers what is involved when overclocking AM2+ processors such as the Phenom II-, Phenom-, or K10-based Athlon 7xxx series processors. But we also want it to apply to earlier AM2 (K8)-based Athlon X2 processors, such as the 4xxx, 5xxx, and 6xxx series. There are some differences in overclocking theses K8 processors, which are highlighted later in this article.

Here are the basic formulas used to calculate the above listed frequencies for AM2+ processors: 

Core Speed = Reference Clock * CPU Multiplier

Northbridge Speed = Reference Clock * Northbridge Multiplier

HyperTransport Link Speed = Reference Clock * HyperTransport Multiplier

Memory Frequency = Reference Clock * Memory Multiplier

If we want to overclock our processor (increase its core speed), we can increase either the reference clock or the CPU multiplier. As an example, the Phenom II X4 940 runs a 200 MHz reference clock and a 15x CPU multiplier, resulting in a core speed of 3,000 MHz (200 * 15 = 3,000).

We could overclock this core speed to 3,300 MHz by either raising its multiplier to 16.5 (200 * 16.5 = 3,300) or by raising the reference clock to 220 (220 * 15 = 3,300).  

But keep in mind that the other frequencies above are also based on the reference clock, so increasing it to 220 MHz will also increase (overclock) the northbridge speed, the HyperTransport speed, as well as the memory frequency. In contrast, simply raising the CPU multiplier would, in turn, only increase the CPU core speed of the AM2+ processors. In the following pages, we will first take a look at simple multiplier overclocking using the AMD OverDrive utility, and then head into the BIOS for more advanced overclocking by raising the reference clock. 

Depending on the motherboard manufacturer, BIOS options for core speed and northbrdige speed will sometimes not use a simple multiplier, but instead a FID (Frequency ID) and a DID (Divisor ID). In this case the formulas would be:

Core Speed = Reference Clock * FID (multiplier)/DID (divider)

Northbridge Speed = Reference Clock * NB FID (multiplier)/NB DID (divider)

By keeping DID at 1, you are back to the same simple multiplier equation above and will see half multipliers 8.5, 9, 9.5, 10, etc. for the CPU. But by setting a larger DID such as 2 or 4, it is possible to end up with much smaller multiplier increments. To complicate matters, the values can be listed as a frequency, such as 1,800 MHz, or as a multiplier such as 9, while you may need to key in a Hex value. For help with this, consult your motherboard manual or do an online search to find the Hex values for keying in your CPU and northbridge FID. 

There are other exceptions and you will not always be dealing with the above multipliers. For instance, the memory frequency is often set in the BIOS by directly choosing DDR2-400, DDR2-533, DDR2-800, or DDR2-1066 rather than by selecting a memory multiplier or divider. Also, the northbridge or HyperTransport link speed options may be the actual frequency and not a multiplier. At this point, try not to be too concerned about these variations but instead revert back here if and when the need arises.

Ask a Category Expert

Create a new thread in the Reviews comments forum about this subject

Example: Notebook, Android, SSD hard drive

Display all 38 comments.
This thread is closed for comments
Top Comments
  • 12 Hide
    xx12amanxx , February 20, 2009 6:27 AM
    It's nice to see articles about AMD cpu's once again! Just goes to show that Tom's is not biased but rather report's on current trend's and competetive product's that the consumer's enjoy!

Other Comments
  • 12 Hide
    xx12amanxx , February 20, 2009 6:27 AM
    It's nice to see articles about AMD cpu's once again! Just goes to show that Tom's is not biased but rather report's on current trend's and competetive product's that the consumer's enjoy!

  • 6 Hide
    Anonymous , February 20, 2009 6:34 AM
    Thanks for rev!
    Things i like to add are that not all CPU's are supported with AOD even having decent mobo, for example my 4850e + 780G. When overclocking NorthBrige you should really pay attention on it's temp, by simply touching it. Recently i overclocked my system by rising FSB and IGP. Looking at temps given by BIOS and some utilities everything seemed to be ok about 50c, but when touching pasivly cooled NB i couldn't hold my finger for second and heat was so great that even CPU got warmer! When i measured it with multimeter it was 85c idle! And i was wondering why on 3DMark i got blue screen... Problem was solved by adding fan in zone of NB.
    Anyway, moral for those who are willing to overclock is - don't relay on temp measurements given by some utilities. Sometimes it's worth double checking or u can burn something easy. :)  Good luck!
  • -6 Hide
    cruiseoveride , February 20, 2009 7:23 AM
    Intel is such a meany. Another wannabe monopoly like Microsoft.

  • -2 Hide
    curnel_D , February 20, 2009 8:36 AM
    AMD overdrive doesnt see my K8 proccessor as an AMD procc. Cute.
  • 2 Hide
    jhanschu , February 20, 2009 10:08 AM
    I realize that the price difference between the "black edition" and normal processors aren't that much, but I have been wondering how well the "vanilla" cpu's would oc. I've done some light searching for anyplace that's done this and haven't found anything other than people attempting to max out the BE's.
    Does anyone know what a good OC on say the X3 710 would be? It's about $40 cheaper than the 720BE and if it could even hit close to 3.0 I would consider it a decent buy.
  • 1 Hide
    DjEaZy , February 20, 2009 3:08 PM
    ... nice one... and for tha fun of it... would be nice to see a 'system build marathon' based on AMD CPU's...
  • 2 Hide
    roofus , February 20, 2009 3:37 PM
    xx12amanxxIt's nice to see articles about AMD cpu's once again! Just goes to show that Tom's is not biased but rather report's on current trend's and competetive product's that the consumer's enjoy!


    I do agree. I honestly don't think TH ever conducted a boycott of AMD. They just needed something worth saying and AMD finally gave them that. Until Phenom 2, they really had not earned recognition for a good year and a half. They didn't have bad products, but very forgettable ones.
  • 2 Hide
    sandmanwn , February 20, 2009 4:39 PM
    easily one of the best articles I've seen here in a long while.
  • 1 Hide
    iamlouie , February 20, 2009 4:53 PM
    It seems like this article was written specifically for me. I recently built a new PC and it has components used in this article and I've also never overclocked a PC before.

    Specs:
    ASUS M3A78-T
    AMD Athlon 64 X2 7750 Kuma 2.7GHz
    Patriot Extreme Performance SDRAM DDR2 800 (PC2 6400)
    GeForce 7600GT 256MB
    XIGMATEK HDT-S1283
    Antec 500w Earthwatts power supply

    My video card suits my current needs but if I upgrade to a 4870/4850, will I have any power issues if I follow this guide word for word considering my power supply is only 500w compared to the 650w the article uses?
  • 0 Hide
    deuce271 , February 20, 2009 5:13 PM
    iamlouieIt seems like this article was written specifically for me. I recently built a new PC and it has components used in this article and I've also never overclocked a PC before.Specs:ASUS M3A78-TAMD Athlon 64 X2 7750 Kuma 2.7GHzPatriot Extreme Performance SDRAM DDR2 800 (PC2 6400)GeForce 7600GT 256MBXIGMATEK HDT-S1283 Antec 500w Earthwatts power supplyMy video card suits my current needs but if I upgrade to a 4870/4850, will I have any power issues if I follow this guide word for word considering my power supply is only 500w compared to the 650w the article uses?



    A single 4850 and a dual core cpu around 3Ghz will be fine on your 500W PSU. If you had a cheap brand 500W PSU, I wouldn't risk it, but a 4850 should be fine for you.

    The 4870 probably would be fine too but you would want to look into that before purchasing/installing the card.
  • 1 Hide
    salem80 , February 20, 2009 7:09 PM
    Phenom II x3 reach 5Ghz on Ice now see
    http://www.tomshardware.co.uk/forum/page-258314_10_0.html
  • 0 Hide
    dimaf1985 , February 20, 2009 10:03 PM
    wow just in time for my upgrade to Phenom II. i know how to OC my K8, but i wasn't sure what the difference would be with a K10. thanks toms.
  • -2 Hide
    JohnMD1022 , February 21, 2009 12:54 AM
    What is the point of posting photos that cannot be read?

    It's as bad as the unreadable color combinations on the AMD website.
  • 0 Hide
    Silluete , February 21, 2009 1:34 AM
    yeah the photos quality very bad, btw i using ecs ECS A780GM-A Black and Atlon64 X2 6000+ why the AOD won't let me touch the OC bar?
  • 0 Hide
    pauldh , February 21, 2009 4:18 AM
    JohnMD1022What is the point of posting photos that cannot be read?It's as bad as the unreadable color combinations on the AMD website.

    Click on the pics to expand and they should be simple to read. ;) 
  • 0 Hide
    pauldh , February 21, 2009 4:22 AM
    RRRThanks for rev!Things i like to add are that not all CPU's are supported with AOD even having decent mobo, for example my 4850e + 780G. When overclocking NorthBrige you should really pay attention on it's temp, by simply touching it. Recently i overclocked my system by rising FSB and IGP. Looking at temps given by BIOS and some utilities everything seemed to be ok about 50c, but when touching pasivly cooled NB i couldn't hold my finger for second and heat was so great that even CPU got warmer! When i measured it with multimeter it was 85c idle! And i was wondering why on 3DMark i got blue screen... Problem was solved by adding fan in zone of NB. Anyway, moral for those who are willing to overclock is - don't relay on temp measurements given by some utilities. Sometimes it's worth double checking or u can burn something easy. Good luck!

    Yes, thanks for mentioning this about checking by touch or probe when raising NB VID and not relying on reported mobo temps for NB temps.
  • -1 Hide
    Anonymous , February 21, 2009 4:42 AM
    Someone please answer me.
    Whether there is any utility (AOD for AMD processors) which can work with intel processors?
    Also, can i overclock from windows if my BIOS doesn't support overclocking?
  • 1 Hide
    pauldh , February 21, 2009 4:47 AM
    jhanschuI realize that the price difference between the "black edition" and normal processors aren't that much, but I have been wondering how well the "vanilla" cpu's would oc. I've done some light searching for anyplace that's done this and haven't found anything other than people attempting to max out the BE's. Does anyone know what a good OC on say the X3 710 would be? It's about $40 cheaper than the 720BE and if it could even hit close to 3.0 I would consider it a decent buy.

    Initial Street Pricing has spaced the X3 710 and 720 apart, but if you look the X3 720 is right now down to $150 on Newegg making it a $30 difference. I’d like to get my hands on a X3 710 myself to test on the Asus M3A78-T. It has a CPU multi locked at 13, so your OC will depend on the reference clock your mobo can hit. I question how far beyond 3.3GHz, especially if considering the X3 710 for the $625 SBM build as we couldn’t pair it with too expensive a mobo, still keeping a nice GPU, and sticking to strict $625. With the right mobo, I’d hope for 3.4GHz or beyond(similar to X4 810), but I have not used one nor even seen anyone’s results, so that’s just a guess. Of course, the flexibility of the Black Edition would be easily worth the extra $30 IMO if not confined to that strict budget.
  • 2 Hide
    pauldh , February 21, 2009 5:07 AM
    iamlouieIt seems like this article was written specifically for me. I recently built a new PC and it has components used in this article and I've also never overclocked a PC before.Specs:ASUS M3A78-TAMD Athlon 64 X2 7750 Kuma 2.7GHzPatriot Extreme Performance SDRAM DDR2 800 (PC2 6400)GeForce 7600GT 256MBXIGMATEK HDT-S1283 Antec 500w Earthwatts power supplyMy video card suits my current needs but if I upgrade to a 4870/4850, will I have any power issues if I follow this guide word for word considering my power supply is only 500w compared to the 650w the article uses?

    I'll agree with Deuce that the Earthwatts 500W would have no problem for the HD 4850 upgrade. With 34A of 12V it should also handle the HD4870 just fine unless you are ridiculously loaded with drives & fans. If you look at the $750 International Challenge article you'll see I paired an OC'ed E8500 and HD 4850 with an Earthwatts 380W and had no issues at all. The last $625 SBM also used a 500W with 34A 12V paired with an HD 4870. I would have easily used the Earthwatts 500W on that system had it been cheaper at the time.
    Congrats on the system; it's very nice. I like the Asus mobo, the Kuma X2 7750 Black is sweet for such a low price, your cooler choice offers great performance and is quiet, the EA500 a solid PSU I use myself. If you want to game a 4850/4870 would do wonders for the system and both are priced right(in the USA anyway).
  • -1 Hide
    iamlouie , February 21, 2009 11:16 AM
    pauldhI'll agree with Deuce that the Earthwatts 500W would have no problem for the HD 4850 upgrade. With 34A of 12V it should also handle the HD4870 just fine unless you are ridiculously loaded with drives & fans. If you look at the $750 International Challenge article you'll see I paired an OC'ed E8500 and HD 4850 with an Earthwatts 380W and had no issues at all. The last $625 SBM also used a 500W with 34A 12V paired with an HD 4870. I would have easily used the Earthwatts 500W on that system had it been cheaper at the time. Congrats on the system; it's very nice. I like the Asus mobo, the Kuma X2 7750 Black is sweet for such a low price, your cooler choice offers great performance and is quiet, the EA500 a solid PSU I use myself. If you want to game a 4850/4870 would do wonders for the system and both are priced right(in the USA anyway).


    Thanks to you and deuce271 for the replies!
Display more comments