Overclocking 101 - Needs Updating

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Section 1 - Preface and Basic Questions
What is Overclocking?
Simply put, overclocking refers to the process of running hardware at a higher speed than it was originall intended/marketed to run at. Overclocking is often abbreviated to OCing.

What can we OC?
Well almost anything that has a clock generator can be made to run at a higher clock. Of course this includes a whackload of useless devices that have clock generators in them so this guide will focus only on the CPU, motherboard and RAM. The videocard is a device that can be commonly overclocked however it will be dealt with in the video section of the forum.

Why would anyone want to OC?
  • For people with older machines and are beginning to have problems running current generation software smoothly, OCing may give the machine the added oomph required to power through the application
  • For some tasks like animation or movie encoding which depends on the speed of the CPU and to a degree, that of the RAM, OCing will help reduce the amount of time it takes for, say, a movie encoding process.
  • Another common reason for OCing is that it's fairly easy to get the performance of a system that has better parts without shelling out the cash for those parts
  • For some people, the 'thrill' or simply 'because they can'

Why wouldn't anyone want to OC?
  • Warranties are voided when you run the system or any components outside of specification
  • People running [serious] servers are more concerned about stability rather than brute force, bleeding edge performance: an extra bit of performance isnt worth a random restart
  • Beginners (to both OCing and computers in general) or those who dont want to risk frying components. The rist of component failure increases if poor/average components are used in the system
  • Users that just upgraded from a really old system -- the performance jump from the upgrade will be so massive that they wont notice the additional performance delta when OCing a bit

Whats the worst that can happen if an OC goes wrong?
There are three general things that can happen if an OC doesnt go as planned, listed from most likely to least likely
  1. The OC fails without causing any damage, permanent or otherwise. This is the most common and is important in determining the maximum amount your system can can handle for an OC. Usually a reboot or a jumper reset is all that is required.
  2. A component gets slightly 'messed' up but is still functional. Sometime you have to run the device in a slighylu underclocked state to maintain stability. This is more common with video card OCs that go wrong and running the card a bit slower than stock clock speed will allow the card to function normally. There are two ways this failure occurs: (1) extended use of a component in its overclocked state (usually this requires both a fairly large OC to start with as well as for the device to be constantly stressed for a loooooong time i.e., years) or (2) user carelessness (OCing is not risk free and there are telltale signs of failure that should be watched for)
  3. A component gets totally toasted and requires replacement. This form of failure almost always has a telltale sign that "something is amiss" and the user has some time to deal with it before it fails outright. If the device fails 'instantly' there are two comments to be made: (1) you pushed it way to hard way too fast (i.e., user fault for not using common sens: you simply cant push a machine that hard that fast) or (2) luck of the draw (and in this case, bad luck)
  4. Total failure of numerous components. Same comment as above however more often then not, the culprits are (1) a bad PSU or (2) an inexperienced OCer wanting to push the system too far, to hard, too fast

Me and my friend have the same system ... but he can OC much better than I can! What's wrong?
Well just because you have the space make and model of hardware doesn't mean you can OC the same amount. There's differences in make/model all the way down to BIOS revisions, motherboard and CPU revisions -- even when all those match identically -- just because your friend can OC to a certain degree does not mean you can too.

How much can I OC my system by?
This has gotta to be one of the most common questions people ask about OCing and the answer is nobody can tell you. This should be somewhat evident from the previous question (i.e., if two "identical" systems have different ceilings than how can anyone tell you how much you can OC by?). There are some general principles but nothing hard and fast
  • Generally speaking you will be bound by a 33% ceiling regardless of what platform you have. There are exceptions left, right and center (but if you were an exception case, you wouldnt be reading this 101 but rather you'd be looking for a 601 or something ;)). What this means is that if you have a 3GHz processor, dont expect to punch past 4GHz
  • Intel systems tend to get bigger OCs because their architectural design facilitates running higher clocks
  • Common sense suggests that the better your parts the more likely you'll be able to get a higher overclock.
 
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Section 2 Part 01

Section 2 - Building an OC System: What to Look For
There are five major component areas that need to be examined for a successful (i.e., significant) OC (some will/have be dealt with in other 101 guides)
  1. Naturally having a good CPU is important: some CPUs are more friendly to OCing than others. Generally, one, two or three models back from the latest and greatest is an ideal OCing processor
  2. Having a good flexible motherboard that will let you get to the nitty gritty features is critical. All the fancy parts in the world wont mean very much if you cant get access to the manual controls that allow you to fine tune your OC
  3. A good cooling solution is critical to ensuring that your system doesnt die of heatdeath (i.e., overheating and burning out). To a degree the motherboard should feature some protection features but usually those features kick in after it's already too late (and your system is approaching fatal temperatures).
  4. Since RAM speed is often determined by mobo/CPU speed, it's important to have memory that scales effectively with the rest of your OC attempts
  5. Having a good PSU is critical: the harder your push your system, the more sensitive it becomes to voltage fluctuations and as such you need a nice solid power supply to ensure your setup gets the clean power it needs.

Which CPUs are OC Friendly? Which will benifit from OCing?
If you've not decided what platform to choose yet, have a look at the CPU 101, for those that have an idea of what platform they want, some processors to consider:
  • For those looking at the AthlonXP or Sempron(462), platforms, consider
    • AthlonXP 2500+ (Barton core, AXDA2500DKV4D) ... this is the lowest model of the AthlonXP running with the Barton core (which features 512K of L2 cache over the 256K on previous models). Being the lowest model, it will have the lowest price tag and also has a decent OC ceiling thus granting an awesome performance return potential
    • AthlonXP 2800+ (Barton core, AXDA2800DKV4D) ... one of the more popular AthlonXPs packing a decent amount of performance for its cost straight out of the box and still has a nice OC ceiling
    • AthlonXP 3000+ (Barton core, AXDA3000DKV4E) ... although this processor starts to become a bit more expensive than it's worth, it has the distinction of being the cheapest/lowest AthlonXP processor featuring a 200MHz core clock (the other Bartons pack a 166MHz core) and thus gives you a slight head start when it comes to OCing the core)
    • Sempron 2500+ (TBredB-Paris based, SDA2500DUT3D) ... again chosen because it's the cheapest model and still has a decent OC ceiling
    • Sempron 2800+ (TBredB-Paris based, SDA2800DUT3D) ... same reasoning as the AthlonXP 2800+, this is a fairly decent chip right out of the box and has a nice balance of price/performance both in stock and OC'd state
    • Sempron 3000+ (Barton, SDA3000DUT4D) ... this is the only Barton based S462 Sempron (thus meaning it packs 512K L2 cache as opposed to 256K) and also is the highest Sempron model available for the S462 platform.
  • For those looking for a Athlon64(754) or Sempron(754) option,
    • Athlon64 2800+ (Clawhammer, ADA2800AEP4AP) .... being the lowest rated Athlon64 this will also be the cheapest Athlon64 and thus be a good price/OCability route
    • Athlon64 3200+ (Newcastle, ADA3200AEP4X) ... choosing not to go for the Clawhammer for this processor was simply based on the fact that the Newcastle would be cheaper
    • Athlon64 3700+ (Clawhammer, ADA3700AEP5AR) ... this is the best S754 processor AMD made to date (dunno if they planning on extending the S754 lineup or not) but if you want to get the most from your S754 box this is the processor to get. Of course, with the pricetag of the 3700+ you should be in the ballpark of a S939 setup
    • Sempron 3000+ (Plaermo Winchester-based SDA3000AIO2BO) ... the lowest S754 model (thus the cheapest), this Sempron should be affordable and being built on a 90nm process gives it a cooling advantage (thus allowing for a higher OC ceiling than the older 130nm-process based chips)
    • Sempron 3300+ (Plalermo Winchester-based, SDA3300AIO2BO) ... this is the latest and greatest Sempron, packing SSE3, being a 90nm processor and supporting AMD64 makes this a very versitile platform to OC from
  • For those looking at the Athlon64(939) platform, have a look at:
    • Athlon64 3000+ (Winchester, ADA3000DIK4BI) ... the lowest grade S939 Athlon64 processor and being a 90nm processor make this a very good choice from both a performance/cost and OCability perspective
    • Athlon64 3500+ (Winchester, ADA3500DIK4BI) ... a midrange (pricewise) processor with good out-of-the-box performance and decent OC ceiling make this an ideal candidate
    • Athlon64 3700+ (San Diego, ADA3700AEP5AR) ... a good processor packing a recent core but without becoming excessively pricey, this is a good processor for those wanting an above-average out-of-the-box setup to start with but without stepping into the "expensive arena"
    • Athlon64 FX53 (Sledgehammer, ADAFX53DEP5AS) ... cheapst of the FX processors for the S939 platform and packing 1MB of L2 and totally unlocked multipliers, this is the cheapest uber-OC chip you can get
    • Athlon64 FX57 (San Diego, ADAFX57DAA5BN) ... the best single-core processor available now, this CPU packs 1MB L2 cache, SSE3 support and a tweaked memory controoler in addition to fully unlocked multipliers for lots of OCing control
    • Athlon64 X2 4200+ (Manchester, ADA4200DAA5BV) ... the lowest model of the dual-core processors and thus the cheapest, this is the best proc to get if you're trying to balance dual-core, price and tons of OC headroom make this a brilliant processor
    • Athlon64 X2 4800+ (Toledo, ADA4800DAA6CD) ... the best all around chip money can buy (and it's going to take a lot of money) but this is a superb platform straight out of the box so OCing it should yield some devasating resullts
  • For those looking at the Pentium4(478) platform, have a look at:
    • Pentium4 2.80 (NorthwoodC) ... an ever increasingly rare processor, this was a great CPU both out of the box and OCd and for a reasonable price
    • Pentium4 3.20 (NorthwoodC) ... a bit more common than the 2.80, this processor also has a bit more OC flexibility due to a higher stock multiplier
    • Pentium4 3.20 (Prescott) ... cheaper than its Northwood counterparts and also significantly hotter and less clock efficient, many enthusiasts have gotten significant overclocks from this processor
  • For those looking at the Pentium4(775) platform, have a look at:
    • Pentium4 520/620 (Prescott/Prescott2M) ... at 2.80GHz this is the lowest and cheapest processor of its series and poses less of a heat-problem than its 478 siblings yet still has room for OCing
    • Pentium4 540/640 (Prescott/Prescott2M) ... very impressive out-of-the-box performance coupled with nice OC capabilities and a reasonable pricetag make this a very respectable processor to buy
    • Pentium4 550 (Prescott) ... this is the lowest S775 processor that supports hacked clock multiplier unlocking on certain motherboards
    • Pentium D 820 (Smithfield) ... this is the lowest modeled Intel dual-core processor available and is quite affordable .. a definite solid candidate for OCing
    • Pentium Extreme Edition 840 (Smithfield) ... this heavy hitting (performance and budgetwise) processor is the best Intel has to offer and OCing it to get all the performance you can may be the only way to relieve yourself of the sting of its cost hehe


On to Part 2 ...
 
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Section 2 - Part 02

Which Mobos are OC Friendly? Which will benifit from OCing?
There are four things to look for when selecting a motherboard for the purposes of OCing:
  • Brand repuation both overall and for the series of processors you're looking to buy (the reasoning is that some brands are much better choices for one particular platform and not for others)
  • The chipset the given motherboard features
  • The flexibility of the BIOS (i.e., some motherboards allow you to tweak multipliers by 0.5x while others allow for a precision of only 1.0x)
  • Any features the board happens to have

A Quick Summary of Suggested Motherboards
It's important to note that ive picked out the flagship model of the given series which means they will tend to be the expensive ones. do note that there are motherboards of the same family as the noted boards which are often much more affordable. It's also important to note that this listing is in no particular order whatsoever.

What Kinda Cooling Considerations Are There?
There will eventually be a cooling 101 written up to deal with this topic in depth but suffice it to say, cooling is a critical consideration when overclocking: the more serious the overclock, the more serious the cooling unit must be.to handle the outputted. Whether you decide to go with air cooling, watercooling or other exotic methods, it's pretty fair to say that the stock cooler is not sufficient.

Your motherboard and/or CPU should have some form of thermal protection (especially so for the more recent models) and you may see evidence of this kicking in as the machine shutting down, throttling itself or rebooting. Failure to address this issue may (and likely will) result in component failure.

RAM Considerations for OCing?
In many cases, when you scale the speed of your system you'll need to scale the speed of the RAM as well (or at least you'll want to) ... having RAM that is able to keep up with your system will eliminate the RAM being a bottleneck on your OC success. Have a look at the RAM 101 for a guide on what to look for and some suggestions.
 
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Section 3 - A Crash Course in CPU and Memory Speeds
This is covered in-depth in the CPU 101 but the idea is:
  • The net speed of a CPU is determined by the product of the core speed (sometimes called the FSB) and the multiplier
  • RAM speed, for processors not based on a Socket754, 939 or 940 pin configuration is often set independently of the CPU clock (or is set as a certain ratio of the FSB speed) however for the specific case of the processors with on-die memory controllers (that is, those that are installed on socket 754, 939 or 940 pin configurations), life is a bit more complicated (or easy)
    • Net CPU Speed = Core x Multiplier (nothing new here)
    • Divider = CPU/DRAM x Multiplier (always rounding up... also note that this number is always bigger than the multiplier)
    • Memory clock = Net CPU Speed / Divider

    Examples
    Given an AMD Athlon64 3800+ (200x12) with the CPU/DRAM ratio as 6:5, the memory clock is determined as:
    Divider = 6/5 x 12 = 14.4 => 15
    Memory Clock = 2400 / 15 = 160MHz

    Given an AMD Athlon64 4000+ (200x12) with the CPU/DRAM ratio of 1:1 (i.e., the ideal standard DDR), the memory clock speed is determined as:
    Divider = 1/1 x 12 = 12
    Memory clock = 2400 / 12 = 200Mhz

    Now if we take an AMD Athlon64 4000+ and overclock it (230x12) again with a ratio of 1:1, the memory clock speed is determined as:
    Divider = 1/1 x 12 = 12
    Memory clock = 2760 / 12 = 230Mhz

    Last example, if we take the same AMD Athlon64 4000+ (230x12) and change the ratio to 6:5, the memory clock is determined as:
    Divider = 6/5 x 12 = 14.4 => 15
    Memory clock = 2760 / 15 = 184MHz
    ​
​
 
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Section 4 - How to Overclock
Technique 1 - Jack the Multiplier
This is the most ideal method as it does not affect anything other than the CPU and so if you mess up, the only thing that gets potentially messed up is the CPU. Furthermore, increaseing the multiplier increases the final speed by the largest steps (increasing the multiplier by 1.0 will increase the net speed by an amount equal to the core speed). Depending on your motherboard, you may only be able to change your multiplier by 1.0. Some motherboards allows changes by 0.5 to give more flexibility/precision.

Now AMD and Intel both realize that people are doing this stuff and thus they are not getting the sales that they want (of the more expensive chips). Intel has responded by upward locking all the multipliers of their CPUs. You can still bring your multipliers down though (we'll see why in a bit). AMD however has approached the issue (as they've always been more partial to OCing) by making two separate product lines, a mainstream line which is upward locked like Intel's and an enthusiast line which is completely unlocked. Also, some Intel processor models (as mentioned above), together with specific hardware, partially unlocked multipliers become an option.

Technique 2 - Raising the Core Clock
This is the probably the most common method for OCing since AMD and Intel have implemented locks on their processors. The good thing about this approach is that you have a lot more control over your OCs i.e., for each MHz you OC the FSB/HTT, you only OC by the amount that is your multiplier which becomes useful as you try and get a feel for your maximum clock. The down side is that you also increase the operation speed of the memory and if you dont have AGP/PCI locks, the speed of the AGP/PCI bus. Not all memory and/or cards can handle the increase in speed so thats why people run into problems.

What do you mean, raising the core clock raises my memory speed? How does this affect me?
You may have seen memory marketed as PC3500 or PC4000 or such -- the slots are designed to operate at PC3200 so how do you think the RAM is marked so high? To get those speeds, you have to increase the ratio of the FSB/HTT because memory speed.

What is all this PCxxxx stuff anyways? What's the speed?
PC1600 = 100Mhz, DDR200
PC2100 = 133Mhz, DDR266
PC2700 = 166Mhz, DDR333
PC3200 = 200Mhz, DDR400
PC3500 = 217Mhz, DDR433
PC3700 = 233Mhz, DDR466
PC4000 = 250Mhz, DDR500
PC4400 = 275MHz, DDR550
The "PC number" comes from the fact that per pair of clock cycles, 16 bytes of data are being transferred (so for PC4400, 16 bytes * 275 = 4400Mbytes/sec)

Technique 3 - A Bit of Both
While it's possible to OC a system purely by increasing the multiplier or by increasing the core clock, another route is a combination of changing (not necesarily increasing) both the core clock and multiplier

Why would I ever want to drop my multiplier?
Although the multiplier allows for the greatest single-step increases in net clock speed, sometimes the increases are too much for the hardware to handle and more precision is required. Suppose for instance we have a FX55 system (configured 1:1) that has a maximum clock of 3.00GHz (i.e., it will not OC any higher)
  • CPU = 200x13.0 = 2600MHz, RAM = 200MHz (Original)
  • CPU = 200x15.0 = 3000MHz, RAM = 200MHz (OC via multiplier increase)
  • CPU = 230x13.0 = 2990MHz, RAM = 230MHz (OC via core clock)
  • CPU = 250x12.0 = 3000MHz, RAM = 250MHz (OC via multiplier decrease & core increase)
As shown above (assuming the RAM can handle the OC), the last configuration nets the greatest performance from both the processor and the RAM.

Ok How do I *Actually* Go About OCing? Gimme the steps please!
Since there are hundreds of board models out there each with its own appraoch to setting clocks and menus and such, there isnt really a be-all-end-all approach to providing a step-by-step method. Generically speaking however the idea is "go into your BIOS, make sure all the controls (clock speeds, voltages etc) are set to manual and then actually go about setting them to the desired speeds". You'll have to have a look at your manual to see how to actually go about doing this.

I have a Dell/HP/Compaq/Packard Bell/IBM/Toshiba etc ... how do I OC?
For the most part you are SOL and as long as you realize this, read on. In some cases (don't count on it though), you can make use of software hacks to overclock your computer. One of the more popular attempts is a via a program called ClockGen. Having a quick glance at the list of supported boards, it's evident that even ClockGen is not directed at owners of OEM systems but you might get lucky. This is the price to pay for buying an OEM system (i.e., they dont want you to OC: they'd rather have you buy a new system from them)

I dont have an OEM system but I dont have any of the controls you're talking about!!
Well there are two generic cases of this happening: (1) you have an older or el-cheapo motherboard where all the clock options are set via jumpers on the motherboard so you'll defiitely have to dig out your manual to see where those jumpers are and how to configure them or (2) your motherboard has a crappy chipset/BIOS which is not OC friendly. This happens a lot with SiS and (to a much lesser degree) Via chipsets. Generally speaking, you can try ClockGen but don't count on it ... those chipsets are generally marketed towards a consumer base both not interested in OCing nor has the [supporting] hardware to do so

Is there a Golden Rule?
Absolutely! And it is "overclock in reasonable increments" -- overclocking 300MHz at a time is both foolish and stupid as 300MHz is too much of a jump to allow you to be able to discern where your actual OC ceiling really is and pushes the system too hard, too fast. A good ballpark number to keep in mind is 5-10MHz at a time on the core clock at a time and checking for stability each time.
 
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Section 5 - What to do when Hardware Doesn't Cooperate
I only OC'd by 30MHz on the core but It doesnt POST!! Does this mean I've hit my ceiling?
Most likely not. This is where the power supply comes in and starts to play as a factor on your OCs. The general idea is that, the harder you push your system, the more power it requires (shouldn't be a surprise there) and as such what this means is that you will have to start increasing the voltage being delivered to your CPU (designated as Vcore).

A good method of approaching this is to OC until you cant boot (this is why you approached it a 5-10MHz at time) anymore and then increasing the Vcore by a single step (usually 0.025v). If that wont boot still, increase it by another step. If three increases on the Vcore still dont allow you to boot, it becomes more plausible that you've reached your OC ceiling. Also note that in systems where, by OCing the core clock, you also increase the memory clock, you may also consider increasing the amount of voltage going to the RAM (designated Vdimm) by a single notch (usually 0.1v sometimes less). You shouldnt however, unless you know what you're doing, go past 2.8v on the voltage for DDR memory and 2.0v for DDR2.

It's also important to note that long term, it's not heat that kills a CPU but rather voltage ... this explains why some guy with a Vapochill unit keeping his box at -10C can still fry his CPU. When you start pushing the Vcore a lot (i.e., say by 0.4v+) you run the risk of long term damage. Same dealy goes for RAM.

When you OC always make sure you keep an eye on your temperatures and voltages to see that the temperatures dont get out of hand a your voltages stay relatively close to expected values. Three tools that come to mind are SpeedFan, MBM5 and for ASUS motherboard users, ASUS Probe. If you dont have an OS installed yet or anything, manual temperature probes as well as the BIOS hardware monitor are good places to start.

It is also important to note that, sometimes, overclocking the core clock will also inadvertantly overclock other things like the AGP or PCI bus. Overclocking friendly boards tend to have 'things' called "locks" that essentially force those devices like the AGP and PCI bus to run at their standard speed yet still running the remainder of the system at a faster speed. Not all motherboards have these locks though and as such you may be running into OC ceiling as low as 10MHz into an overclock ... do some research on your motherboard model to find out. Also, not all motherboards that have such locks have functional locks: a good example of this is the ASUS A8V Deluxe, Rev 1.xx ... the locks were supposedly in place but it's well known that they really arent functional and should be treated as it they were not actually there.

Once you've really hit your maximum overclock, dial back 5MHz or so and then do serious testing for system stability.

I OC'd and now when i turn my computer on... nothing happens!!!
Well there's two causes for that (1) you OC'd too much for the system to handle (i.e., you've hit your ceiling). See the previous question on more about that but you may have to reset your CMOS/BIOS (see your manual on specific instructions on how to do that) or (2) your hardware is fried either because it overheated (for which there were telltale signs) or simply because it was pushed too hard and decided to die (quite unlikely but it happens and its a risk you run when OCing)
 
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Section 6 - Measuring Success
Now that you're statisfied with OC you've got and you want to test for long term stability as well as performance gains, some programs to keep in your toolkit are
  • CPUz is a simple program that displays all the major points of your system in a compact and easy to navigate interface. It also supports an online database of overclocks and such
  • SiSoft Sandra is the oldschool tool used to measure both system and more so, [theoretical] memory performance. As a all-in-one suite it also presents system information and allows for system burn-in testing. A similar and free program is PCWizard and is made by the CPUz people. One last program which is also free and somewhat comment is Everest Home Edition
  • Prime95 This is used to both benchmark system performance but more importantly, the torture test lets you test your system for stability ... if you can run the torture test overnight without issues then its fairly reasonable to suggest that the system is stable
  • SuperPi. This is used to test both stability as well as processor/RAM performance by calculating Pi to so-however-many decimal places
  • PiFast. This program serves the same purpose as SuperPi however it gives more precision in calculation times (0.1 of a second compared to 1 second) as well as allowing you to testing specific amount of memory (useful for really testing your memory for stability)
  • 3dMark01 Classic benchmarking program
  • 3dMark03 Classic benchmarking program
  • 3dMark05 Classic benchmarking program
Until you are certain of your system's stability, it's adviseable to keep a temperature/voltage monitoriing program open while you run these tests so that you can respond to (or be aware of) potential stability/lifespan issues.
 
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