Phenom II Overclocking Guide
So you're here looking for some good info to help you learn how to overclock your Phenom II (hereafter referred to as PhII's). And in the absence of a dedicated PhII guide, I decided that I would try my hand at helping everyone out.
First off, I do not claim to be the most experienced user/overclocker out there, or even on this forum. That said, I do feel that I have a pretty good handle on things, and have helped out enough people that are new to this, that I know mostly what they need to know to get started with their own OC.
A few Questions before we get started:
Do you have an OEM (prebuilt) computer?
I have seen a lot of people ask for help OC'in a prebuilt computer... which unfortunately, you cannot do (except through software, and we really don't recommend that, because almost all OC'in programs have terrible reputations as far as system stability is concerned [AOD is one notable exception]).You are unable to OC because the mobo is locked... meaning, none of the options in the BIOS that you need are able to be changed. Now, you can get a cheap mobo if you really want, but you should know a few things first. If that's what your plan is, read through THIS, just so you're aware of what will happen.
Do you have proper cooling?
OC'in is basically pushing a chip past its designed speed, so it only makes sense that the cooling system would need to be up to the larger demand that is placed upon it through the added clock speed and voltage. Now, you can OC some with a stock cooler, but we recommend that you keep your CPU under about 55 degrees Celsius for its full load temp, because that is the low end of AMD's max rated temps. So some OC'in can be done with a stock heatsink, but don't expect to get as far, because you wont be able to push the voltage much past stock. For more information about how high performance heatsinks work and which ones to look for, or how you can make do with your stock cooler, check HERE and HERE.
Can the rest of your machine handle it? (PSU and cooling check)
Often people that are looking to OC are looking for improved performance in games, which often includes a new graphics card and the aforementioned overclocking. An overclocked CPU will draw more power than it did at stock clocks, and better graphics cards almost always require more power, so you need to make sure your PSU can power all of the upgrades. While this is less of a problem with enthusiast built computers, for people looking to upgrade or build for the first time, it is important to mention that the PSU is something that you should never skimp on. The PSU can make or break the whole system (literally), so I don't see why people would try to just barely get by with one. For more reading on this topic, check THIS out, as it can help you figure out how much power you really need, and which brands to look for.
Are you looking at upgrading to a PhII?
I did this same thing, and decided that I would post some benchmarks when I made the switch from my 4600 brisbane to my 720 BE. You can see the results of the test HERE. Hopefully that will help you decided (as if the barrage of professional reviews on the web weren't enough to make up your mind).
Some important info before you start: (Do you have a Black Edition or not?)
There are two ways to OC the AM3 chips, and both have their own advantages. The first way is for those of you that bought a Black Edition processor. You probably know that you can increase the clock speed by just raising the CPU multiplier. The advantage of this is that you can increase the clock speed easily, without changing any of the other speeds or settings (because the reference clock isn't being adjusted, no other settings will need to be changed).
The second way is by raising the reference clock, This is what those of you that have non-Black Edition processors will have to do. It will sound more complicated, but in all reality, its not that difficult, its the way that people have been overclocking for ages, and it has the added bonus that you can overclock things other than just the CPU clock speed (namely the ram, as well as the Northbridge and Hypertransport speeds), which can provide additional performance benefits over just changing the CPU clock speed. So, like many other things, the additional time that is spent perfecting the OC this way, can definitely pay off for those of you that are looking for the most performance that you can get.
While there are various methods and theories to achieve this end, I will show you how I generally do it. It is slightly less scientific than the one that is laid out in Durches guide, but it is also faster to do. If you want the more precise method, try looking at Durches excellent AM2 guide, you will just need to apply some of what you learn here to that guide, as the AM3 chips are slightly different, but the concepts are almost identical. Done properly, each should get you about the same max OC, so just take your pick as the methods can easily be incorporated into the same OC.
Reference clock overclocking:
We'll start with the old school way of OC'in, as this is the one that most people struggle with. Start out by raising the reference clock a few MHz at a time (try 5 or so to begin with). The overall clock speed is based on the reference clock and the CPU multiplier, so by changing this, you will be raising this by 60-100MHz per step. We do it a little bit at a time, because when instabilities surface, it is infinitely easier to find out what is the cause, when you only have one or two things that should be causing it. After each increase in speed, you need to check for stability.
Now, to be considered fully stable, you need to run a program like Orthos, OCCT or prime95 for at least 6-12 hours, but while working with your OC, you don't need to run it near that long. You're just trying to find out if its even close to being stable at the speed it is at right now. In general, if I pass one of the above tests for more than 5 minutes, I'll reboot and continue pushing the OC. Run the longer tests when you think you're where you want to end up, and if it fails before those 6-12 hours, then lower the OC, and try running it again. Otherwise, you're risking running an unstable system for every day, 24/7 usage. Trust me, you do not want to do that, its not worth what it costs for those few additional MHz.
*(primarily you risk corrupting your operating system, as a system that will run your OS, but not pass a stability test will start to perpetuate small errors, and those will eventually be saved to the HDD. That translates into one day your computer runs just fine, the next it wont boot, and there is really nothing you can do to salvage the OS other than to try and save your data, and then reinstall).
Following this pattern, you should likely get the reference clock to about 220-235 before you run into any problems (not a guarantee, but that is based on my experiences here). So now we have a system that is unstable. I will tell you right now, that about 85-90% of the time when you become unstable at this point, its because of the ram being overclocked. Because you have been OC'in with the reference clock, you have also been raising the speed of the ram, because like I said earlier, it is tied to pretty much everything. You can check if it is the ram by running memtest (tests 5 and 8 are the most rigorous, so we usually recommend you run those about 30 minutes each). You should know pretty quick if the ram is your problem.
What to do when you encounter ram instability:
To get you past system instability in this case, all you need to do is lower the ram speed setting in the BIOS to the next lowest setting. (If you're running your ram at DDR1333 in the BIOS, then change the setting to DDR1066 for example). The ram speed setting is what we like to call a “divider”. In 'normal speak' this means that the speed of the ram is based on a simple formula. When you change the speed setting to a lower value, you are really just dividing by a larger number, so the speed of the ram goes down. To get a much more in depth understanding of how this works, read THIS. For a more basic understanding, I would recommend checking THIS about memory speed and their timings, as many people get them confused.
North Bridge, Hypertransport and IMC:
So now you have likely overcome your first instability, and are just cruising right along. The next issue you are likely to have when doing this, is either the NB (NorthBridge) or HT (HyperTransport). The NB effects the speed that the ram communicates with the CPU, while the HT deals with how fast the CPU communicates with the rest of the components on the motherboard (it essential replaced the FSB for those of you intel (or pre socket 754 AMD) owners out there). The NB and HT are related, and in fact, you can't set the NB speed any higher than the HT speed. Overclocking the HT speed has been shown to provide only marginal improvements in performance (perhaps in cases when multiple high end GPU's are being used). In fact, most of the time people find that there is almost negligible difference in performance between overclocked and underclocked HT's. This is primarily because the HT has such a large bandwidth, that it is rarely saturated with information, so an increase or decrease in speed often is hard to notice. You can see that HERE.
*The HT is really more important for multi-socket Servers, as the communications between CPU's and components becomes much more important.
The NB is where things can get quite confusing for people. The NB is between the CPU and the IMC, and the IMC is the Integrated Memory Controller. So you can see that having this go faster will make the memory faster. So obviously the NB speed can be very beneficial to increase. The memory access times and read/writes often go down quite a bit when the NB is OC'd. In fact, this is part of why the memory speeds of the PhII's are so much faster than the original phenoms (you can see this HERE). From tests and reviews that I have seen, you can expect that most AM3 chips will hit 2.4-2.8GHz on the NB, although that will likely require some additional CPU/NB voltage and/or cooling to ensure stability. Read through THIS thread if you have more questions about NB and NB/CPU voltage and settings, it is one of the better sources I have found for good info on that topic.
Another excellent source is has been provided by our very own "Tator Tot", and it does a great job explaining what the voltages actually do, and what they are often referred to in the BIOS. Check it out HERE.
Right now we're still on our quest for more clock speed, so if you encounter instability right now, try lowering the NB and HT multipliers, so that their speeds are closer to the stock values. You should be fine if the values are within a few hundred MHz or so (obviously lower speeds would work as well).
If the OC is still unstable:
If you do that and the OC is still unstable, the chances are just that you need more voltage (usually marked as the Vcore in the BIOS). While what increasing the voltage does is actually quite technical, its effects are essentially to help stabilize an unstable processor, but it does this at the price of increased heat, and higher power consumption. In general, there is a point of diminishing return for increasing voltage for higher clock speed. You should be able to notice this as it will take much larger increases in voltage for the same increase in clock speed. Regardless, increase the voltage a little (I generally do one increment at a time, as you don't want to increase the voltage more than necessary) and press on. Keep in mind that you should keep an eye on the temps, and that we usually strive to stay under about 55c for the loaded temps (the temps while you're doing the stress testing).
*Note that AMD has noted a max safe voltage of 1.55v for the Phenom II's, although generally I would not recommend going above 1.5v for 24/7 use.
Continue to do this until you have reached a point where no matter what you do, you cant seem to get any farther with the OC, no matter what you try to adjust at least one thing will hold you back. Sometimes it will be voltage, for others it will be temps, and even for others it will be the processor has hit its maximum performance.
Once you get your max clock speed, try changing some of the settings, and see if you can't squeak a little more performance out of it, by raising the ram, HT and NB speed settings one at a time (one at a time is important, otherwise figuring out what caused what is almost impossible). You can try increasing the voltage to each of those if they are borderline stable, and that can often give you that little bit that you needed to get the OC stabilized. I will say that generally raising the NB voltage has more of an effect than the others, especially at higher reference clock values.
Once you're set on your OC, don't forget to run a stability test for at least 6-12hrs.
For those of you with Black Editions, you can just increase the CPU multiplier until it is unstable, increase vcore to fix it, and keep going until you hit the limits on either temps, or voltage. Of course, you could also use some of the principles that you learned reading through here to max out your OC. You just have the additional flexibility of changing your multiplier. For instance, you have the ability to increase your multiplier farther than anyone else, which lets you do something like this. Lets say that you are stable at 3.6GHz (200*18) but not anywhere past that. To improve the total system performance, you could lower the multi to 17 and raise the reference clock to 211, and achieve slightly better performance. Doing it this way you also seeming dodge most of the bullet when it comes to having to tweak the ram speed settings and the like, since the reference clock is still so low.
*Note: You will "usually" be ok using the above method, but overclocking is anything but a guarantee, so depending on your setup, you still might need to tweak things a bit.
Good luck, and if you have any questions or are still running into issues, don't forget to post your problem (not in this thread though, make another one ), that's what the forum is for
You might have people tell you that it is better to have really high reference clock values, and a lower CPU multi (All CPU's have their multiplier unlocked in the downward direction, but black edition chips have it unlocked upwards, which is what makes them special). That information is not very relevant to AMD chips anymore as all AMD chips since the 754's have used the reference clock and HT, instead of the front side bus (FSB). Since the overall HT, NB and clock speeds are what are important, it isn't as important how you get there when it is based off of the reference clock. That advice is much more applicable for CPU's that still utilize the FSB. The FSB is used to communicate between the CPU and everything else on the motherboard (ram, GPU's, PCI, everything). So having the FSB be faster would help the computer be faster in general, since everything was running faster.
This is also a slightly outdated concept in terms of max clock speed as well. With most PhII's being able to reach 3.6-4GHz, it would take reference clock speeds upwards of 300 if a low CPU multiplier was used. Most AMD boards will have a hard time reaching those speeds, so in general I would leave the CPU multiplier at its stock value, in order to get the max overall clock speed.
I've tried to include many useful links in this thread, but most of them are "hidden" in the main text, For this reason I'm going to be listing them here for easier access, although I'll still be leaving them where they are as well.
Official AMD "Dragon" Overclocking guide
Durches AM2+ Overclocking Guide
Important info for OEM computer owners:
AM2 (brisbane) vs PhII 720 BE "review"
AM3 Motherboard buyers guide
How Heatpiped coolers work
Guide: Temperatures, heatsinks, monitoring and more
PSU Basics/Buyers Guide
Ram Basics: For those that don't speak nerd
HT Link explored
NB Speeds, which is best?
Tator Tots "AMD Overclocking Voltages Explained"