Overclocking CPU & Memory

General

What is overclocking?

Overclocking is the process of increasing the clock frequency of your Central Processing Unit (CPU), Graphical Processing Unit (GPU), Memory, PCI, and/or AGP devices. In other words, making your computer run faster without having to spend the money on upgrades.

What is the risk of overclocking?

	- In most situations, Overclocking will void the warranty of your equipment.
	- The lifespan of the CPU and other devices will be shortened.
	- You could potentially destroy your CPU, memory, motherboard, and other expensive items.
	- Room temperature is likely to increase.
	- Your system could become unstable
	- You might become an OC Addict

What is the Front Side Bus (or FSB)?

FSB is also known as the Memory BUS or System BUS and connects the CPU with the main memory and is used to connect to other components within the computer. The FSB can range from speeds of 66MHz, 100MHz, 133MHz, 266 MHz, 400MHz, 533MHz and beyond.

What is system bus?

The bus that connects the CPU to main memory on the motherboard. I/O buses, which connect the CPU with the systems other components, branch off of the system bus.

What is backside bus?

A microprocessor bus that connects the CPU to a Level 2 cache. Typically, a backside bus runs at a faster clock speed than the frontside bus that connects the CPU to main memory. For example, the Pentium Pro microprocessor actually consists of two chips -- one contains the CPU and the primary cache, and the second contains the secondary cache. A backside bus connects the two chips at the same clock rate as the CPU itself (at least 200 MHz). In contrast, the frontside bus runs at only a fraction of the CPU clock speed.

What is a bus?

Usually a big long yellow thing that.... err... A Bus is a collection of wires through which data is transmitted from one part of a computer to another. You can think of a bus as a road or highway on which data travels within a computer. When used in reference to personal computers, the term bus usually refers to internal bus. This is a bus that connects all the internal computer components to the CPU and main memory. There's also an expansion bus that enables expansion boards to access the CPU and memory.

All buses consist of two parts -- an address bus and a data bus. The data bus transfers actual data whereas the address bus transfers information about where the data should go.

The size of a bus, known as its width, is important because it determines how much data can be transmitted at one time. For example, a 16-bit bus can transmit 16 bits of data, a 32-bit bus can transmit 32 bits of data, and a 64-bit bus can transmit 64 bits of data. - If your still thinking about the highway analogy, a larger road can allow more cars to travel than a smaller road.

How does FSB determine CPU speed?

CPU speed is determined by the following formula:

FSB x Multiplier = CPU Speed

For example, if you had a FSB setting of 133MHz and a 10x Multiplier, your CPU speed would be 1330MHz or 1.33GHz.

Processor

How is a processor overclocked?

The most common (and simplest) way to Overclock a processor is by simply raising the Front Side Bus (FSB) from within the BIOS. The process is the same with both AMD and Intel CPUs. Simply enter the BIOS on system startup, find the setting for the FSB and increase that value. - If you are unsure where this option is in the BIOS, take a look at your motherboard manual, as it should have that information for you.

My CPU says that it has a 266, 333, 400, 533, or 800 BUS speed, how is that?

Newer CPUs now "double pump" or even "quad pump" the FSB, this is similar to how DDR memory works. For example, the 333Mhz BUS on a processor take a 166Mhz FSB and "double pumps" it.
166Mhz FSB x 2 = 333Mhz

Similar to that, the 533MHz BUS processors are "quad pumped".
133MHz FSB x 4 = 533MHz

What's up with the AMD XP names?

AMD processors are not named according to the speed at which the processor runs, instead they are name according to how that particular processor matches against an Intel P4 processor. For example, the AMD XP 1800+ runs at 1.53Ghz, but its performance is equivalent to a Intel P4 1.8Ghz.

Here's a few quotes from AMD:

	- "Over the past 20 years end users have come to view higher performance as being synonymous with higher frequency. AMD believes that what people really care about, however, is not the frequency of their processor, but the performance it delivers from their applications. While processor frequency contributes to overall CPU performance, it is not the only factor."
	- "To the end-user, the ultimate benefit of processor performance is how fast their applications run. Performance to them, simply put, is the amount of time it takes to perform a given task. With that in mind, the processor that performs a given task in the least amount of time has the highest performance. Increased performance implies reduced execution time. Historically, this has been measured through a variety of benchmarks. When comparing the performance of processors that execute the same instruction set, such as the x86 instruction set in PCs, performance is defined as: The work done by the processor in each clock cycle (represented as instructions per clock - IPC) times the number of clock cycles (represented by frequency)"
	- "PC buyers usually rely on the clock speed (megahertz) of a PC's microprocessor to determine their purchasing decision. Because the industry lacks a simple, universally accepted way to judge performance, users have become conditioned to substituting clock speed to gauge how fast their applications will run."

Ok, now can you translate the AMD XP names to speeds for me?

	1500 - 1.33 GHz
	1600 - 1.40 GHz
	1700 - 1.47 GHz
	1800 - 1.53 GHz
	1900 - 1.60 GHz
	2000 - 1.67 GHz
	2100 - 1.73 GHz
	2200 - 1.80 GHz
	2400 - 1.93 GHz
	2500 - 1.833 GHz
	2600 - 2.133 GHz
	2700 - 2.17 GHz
	2800 - 2.083 GHz
	3000 - 2.167 GHz
	3200 - 2.20 GHz

Can the multiplier be changed?

This answer is two fold:

	Intel Processors: Older Intel Processors (P2? and earlier) the multiplier could be changed in the same way that the FSB can be. Allowing you to OC by increasing one or both values. This caused a problem, as many resellers started Overclocking the CPUs and selling slower CPUs as if they were faster. Because of this Intel locked the multiplier inside the CPU and it cannot be changed.
	AMD Processors: AMD CPUs come from the factory with the Multiplier locked, however unlike Intel CPUs, an AMD can be unlocked. This was done by AMD for those people like us, who want to Overclock.

How is the multiplier unlocked on an AMD?

	AMD Duron and Thunderbird CPUs can be unlocked via a method that has been titled, "The Pencil Trick." Mainly because, all it requires is a standard pencil. You can find the OverClockersClub guide on how to do the "Pencil Trick" here.
	AMD Athlon XP/MP Processors are a bit more complicated when it comes to "unlocking." However, the good folks at HighspeedPC have developed a kit that can be purchased to make unlocking the Athlon XP/MP CPUs much easier. The kit can be found here.

Can the CPU be overclocked without going into the BIOS? -or-

The BIOS has no FSB setting, can the CPU still be overclocked?

In most situations, the CPU can still be Overclocked. There are several programs available that allow you to OC without having to enter the BIOS. Two of the most common are CPUFSB and CPUCool These programs may not work on all motherboards, and this guide does not go into detail of how to use them. Some motherboard manufacturers also include overclocking tools, Giga-Byte for example bundles EasyTune with most of it's motherboards.

How can a system be stabilized after overclocking it?

If the system becomes unstable after increasing the FSB and/or Multiplier, there are two options:

	1. Lower the FSB/Multiplier slightly till it becomes stable
	2. Increase the Core Voltage (aka vCore) of the CPU

Increasing the vCore of a CPU may help stabilize the system by providing the CPU with an extra boost of current. This increase to the vCore has one nasty side affect: increased heat. The increase of heat is explained as Joules Law, which Im not going to cover.

Cooling

How does cooling play into overclocking?

Like all Integrated Chips (ICs) and electronic devices, the CPU will perform better and last longer when it stays cool. When you Overclock a CPU it creates more heat than it would under normal conditions. A cool CPU is a happy CPU. This also applies to other devices in your computer: Video card, RAM, sound card, and other devices.

What is a safe temperature for a CPU?

AMD and Intel both have maximum temperature ratings for their CPUs listed around 80C. If your CPU gets this hot, youve got some serious problems. Most people try and keep the CPU temperature below 40C at idle and below 55C at load.

What is the best heat sink available?

As technology improves, companies are always coming out with a new heat sink or Fan that has the edge over the competition. Some of the most commonly used heat sinks among Overclockers included those made by Thermaltake, Swiftech, and Thermalright. Check out the Overclockers Club review section for reviews on various heat sinks to see what is right for you.

How can temperature be lowered more? - "Super cooling"

If standard air cooling isnt getting the job done, or has become too loud for you. There are a few more options that can help cool a hot CPU. Those these methods tend to be a bit more expensive than a regular heatsink/fan.

	- Water cooling
	Peltier/TEC cooling
	Vapor Cooling
	Liquid Nitrogen Cooling

The methods listed above are beyond the scope of this document, and may be covered in future guides/articles.

In addition to the "Super Cooling" methods listed above, a few things can be done to help lower the temp of your system a few degrees.

	The use of rounded cables, or cable ties to allow air to move easier through the case
	Additional or larger case fans to bring in cooler air, and exhaust the hot air from your case
	Removing the side panels of the case
	Using an Aluminum case instead of a thick steal case
	Lowering the room temperature will also help

What is thermal compound? -or-

Why is thermal compound used?

Due to the machining process used in making heat sinks, just about every heat sink will have a rough surface. To the human eye it may look flat or even feel smooth, but there are microscopic groves in the surface. These groves will trap air between the heat sink and the CPU, and cause a poor transfer of heat.

Thermal compounds such as Artic Silver and Nanotherm are used to fill these groves and help transfer the heat from the CPU to the heat sink.

Is thermal compound required?

While, some people have run AMD and Intel processors without any thermal compound at all, it is not recommended. It can cause you temperatures to be extremely high, and it may even void your warranty.

Memory

What are the different types of memory?

	DDR RAM - (Double Data Rate) pretty much the only thing used anymore. Runs @ FSBx2
	SD RAM - (Synchronous Dynamic Random Access Memory) Old school, still used in some servers and older computers. Not used on newer systems.
	RD RAM - (RAMBUS Dynamic Random Access Memory), dead. - Used on some of the early P4 systems. I say again, dead.

What are the various speeds for DDR?

Starting from the slowest and working to the fastest, memory speeds are as follow:

	PC2100 = 266
	PC2400 = 300
	PC2700 = 333
	PC3000 = 366
	PC3200 = 400
	PC3500 = 433
	PC3700 = 466

Can memory (SDRAM/DDR) be overclocked?

Yes. As when Overclocking the CPU, enter the BIOS and look for the memory settings - if you cannot find it, take a look at your motherboards User Manual. Look for the options CAS Latency and Timing. These Options need to be lowered in order to Overclock the memory. CAS 2 Timing 1 will run faster than CAS 2.5 Timing 2.

What is CAS?

"CAS" is short for "Column Address Strobe". A DRAM memory can be thought of as a matrix, kind of like a spreadsheet with memory cells instead of numbers and formulas. Like the spreadsheet, each cell has a row address and a column address (like "AA57" or "R23C34" in the spreadsheet). As you might have guessed, there is also a RAS signal, which is shorthand for "Row Address Strobe".

What is latency?

Latency refers to the time that you are waiting to get what you need. Merriam- Webster dictionary defines it as "the interval between stimulus and response".

How does CAS work?

To understand this let's walk through a simplified version of how the memory controller actually reads the memory. First, the chip set accesses the ROW of the memory matrix by putting an address on the memory's address pins and activating the RAS signal. Then, we have to wait a few clock cycles (known as RAS-to-CAS Delay). Then, the column address is put on the address pins, and the CAS signal is activated, to access the correct COLUMN of the memory matrix. Then, we wait a few clock cycles -- THIS IS KNOWN AS CAS LATENCY! -- and then the data appears on the pins of the RAM.

Can I mix-and-match different memory modules of different speeds?

Yes you can. Doing this will have no impact on total amount of memory, however the speed of the memory will be impacted. If you mix 512M PC2100 with 512M PC3700, you will still have 1024M worth of memory, however you will be limited by the speed of the PC2100.

In addition to this, if you are using more than one memory module, it is recommended that you use the same brand and type of memory to avoid any type of conflicts.

Video Cards

Can a video card be overclocked?

Yes, ATi and nVidia cards can all be easily Overclocked.

ATi Graphic Cards: Require the use of a program to Overclock the graphic card. The most popular programs are Raid-on Tweaker and Powerstrip

nVidia Graphic Cards: The most common method requires the latest drivers for the GeForce 3, 4, and FX as well as a registry tweak called Cool Bits. After the registry tweak, an option will become available in the display properties that allows the GeForce to be Overclocked.

Powerstrip can also be used to Overclock nVidia GeForce video cards