Overclocking Guide

Introduction

This guide has been written to help overclocking newcomers get started on the road to mad overclocking skill. Intermediates can also learn a thing or two from this guide. Hope you enjoy it!!

Table of Contents:

What you need to OC
Terms/Definitions
The Process/Theory of OCing

What You Need to Overclock Your CPU/Mobo/Memory

1) A motherboard (mobo) that allows you to manually change at least the front side bus (FSB), or multiplier.

2) Adequate cooling for the CPU. What is adequate depends on how far you want to push your system, what vcore (CPU voltage) you’re willing to use, and your specific chip model. You can overclock w/ a stock AMD heat sink (HS), but better cooling = higher speeds (generally). Use a program like MotherBoard Monitor to check your temps. If they're above say 48C don’t even bother overclocking your CPU until you have upgraded your cooling. Though you can overclock your FSB and lower your multiplier in order to keep your CPU at stock speed.

3) Common sense, general computer knowledge, luck, and good memory helps.

Terms/Definitions

FSB - is the speed at which your CPU, memory, and motherboard transfer data. A higher FSB means higher bandwidth, and performance. Your motherboard and memory will limit your max FSB when overclocking. Generally, your CPU will not, though there have been exceptions.

PCI Bus - is the frequency at which your hard disk drive (HDD), PCI cards, USB ports, etc. communicate with your motherboard. The stock speed is 33.3mhz. Increasing the PCI bus usually doesn’t increase performance noticeably. Running your PCI bus too high can cause PCI cards not to work, USB to stop functioning (rarely), or HDD corruptions (most common) where you could potentially lose all of your files and have to reinstall everything. If you're using a VIA chipset or any other motherboard where your FSB is divided by 1/4, 1/5, or 1/6 to obtain your PCI bus, make sure the PCI bus never goes over 38mhz at the very MAXIMUM... unless you don’t care if you lose everything.

AGP Bus - is the bus speed your accelerated graphics port and graphics card will run at. On motherboards w/ dividers, AGP bus = the PCI bus x 2. Higher bus speed mean more bandwidth. However, most graphics cards do not need anymore bandwidth than they already have at 66.6mhz. Though you might see a very small increase in 3D benchmarking scores by it being higher.

Multiplier - is what your FSB will be multiplied by to get the end CPU clock speed. Most mobos allow you to adjust this by .5 increments.
Multiplier x FSB = CPU Clock Speed

CPU Cache - is the memory that a CPU has within its self (onboard). There is the level-1 (L1) and level-2 (L2) cache. L1 is faster. Generally, the L2 cache is bigger (because it’s cheaper to manufacture). The size of the caches depend on the processor’s core.

Voltages:

Vcore (vcc) - is the CPU’s core voltage. The higher the voltage, the faster the clock speed the CPU will be able to run at, and the hotter the CPU will get. And yes, there is a point at which more voltage will hurt your overclock.

Memory voltage (vdimm) - The more voltage, the higher the FSB your memory will be able to hit; and/or the better the memory timings your memory will be able to run at. Some memory modules like higher voltages more than others.

Vdd voltage - is the voltage supplied to your north bridge (the big chip that probably has a heatsink on it on your mobo). Generally, the higher the voltage the higher the FSB your motherboard can obtain.

AGP voltage - is the voltage supplied to your AGP card. Raising the voltage to anything above stock (1.5v) is not recommended. This voltage will not help you overclock your GPU further. It will only enable you to increase the AGP bus, which in most cases, doesn’t increase performance by more than a very small fraction. Increasing this voltage for an extended period of time can cause damage to your video card.

CPU/RAM Ratio, FSB/RAM Divider, etc. - This allows you to run your mobo and CPU at a different clock speed than your memory. However, generally w/ AMD boards, a ratio of 1 (1:1, 3/3, 4/4, 5/5, etc) will yield the best performance. Running your mobo and CPU at 200mhz FSB w/ a memory ratio of 6:4 (memory running at 133mhz) will not be very advantageous.

Memory Timings/Delays - are how many cycles your memory is delayed between certain operations. Different memory have different stock timings. Lower timings are better, but the lower the timings, the lower the max FSB that can be obtained by the memory. Example of very good memory timings:
CAS Latency: 2
RAS/Row Precharge (tRP): 2
RAS-to-CAS Delay (tRCD): 2
Row-active-delay (tRAS): 6

CAS - CAS latency is the number of clock cycles between the memory receiving a "read" command and actually starting to read.

RAS/Row Precharge (tRP) - This Precharge to Active timing controls the length of the delay between the precharge and activation commands.

RAS-to-CAS Delay (tRCD) - This timing controls the length of the delay between when a memory bank is activated to when a read/write command is sent to that bank.

Row-active-delay (tRAS) - The Active to Precharge timing controls how soon after activation the access cycle be started again.

DDR Memory Clock Speeds/Ratings:

Double Data Rate (DDR) memory transfers data at double the rate of your FSB. The PCxxxx rating tells you the maximum megabytes per second that the memory can transfer at the given frequency (FSB). Where xxxx = MB/s. For example PC2100 memory has a bandwidth of 2100MB/s (2.1 GB/s). When talking about FSB I will refer to the actual frequency; not the DDR FSB, which is also referred to as the “effective” FSB. Here’s a table of ratings:

PC4000 = DDR500 = 250Mhz actual FSB
PC3700 = DDR466 = 233Mhz actual FSB
PC3500 = DDR433 = 216MHz actual FSB
PC3200 = DDR400 = 200MHz actual FSB
PC2700 = DDR333 = 166MHz actual FSB
PC2100 = DDR266 = 133MHz actual FSB
PC1600 = DDR200 = 100MHz actual FSB

Common Socket A (467) Chipsets:

A link to a thread on chipsets will be placed here later.

The Process/Theory of OVERCLOCKING!

You should check out this thread to see what kind of overclocks to expect, and what core you have (if you don’t already know).

Overclocking Basics:
CPU Speed = FSB x The Multiplier. Note: that a system clocked at 210 x 10 = 2100mhz will perform better than the same system clocked at 200 x 10.5 = 2100mhz. This is because your FSB affects not only your CPU, but your motherboard, and memory as well. But because you’re also overclocking your motherboard and memory, these components can limit your max FSB. Your motherboard may be able to run at 220mhz FSB, but if your memory can only run at 200mhz, then that’s where you’re FSB overclock is going to have to stop (unless you buy better RAM). It is also possible that your motherboard will stop you before anything else does. When overclocking hardware for the first time, it’s a good idea to find out how fast each component can run individually. Due to concerns w/ the PCI bus, sometimes this can be a bigger challenge for those w/ out a nForceII chipset. If you do not find your max overclock for each component, when you hit a wall, it will be harder to deduce what is holding you back. Here is the general process of overclocking your CPU/mobo/memory. The options you have in your BIOS totally depends on your chipset, motherboard make/model, and sometime your BIOS version. Your options may just be named differently or you may not have them. It’s up to you to learn how to use your BIOS. Use google and/or your manual to figure out how. If you don’t have the options you want... buy a new mobo.

Finding the max FSB for your motherboard:
1) Insure you have good or sufficient cooling for your CPU!

2) Boot into your BIOS settings.

3) Lower your multiplier to a low setting (5-8).

4) Raise your memory timings, and/or change your CPU/memory ratio so that your memory’s FSB is always at/below it’s rated speed. This should insure that your memory won’t be limiting your FSB, just your mobo.

5) Disable useless BIOS features (depends on your mobo, but CPU speed spectrum, throttling are common ones).

6) Increase your mobo’s voltage (vdd) as high as you safely can. Most motherboards don’t allow you to increase your vdd more than is safe (1.6v-1.7v or higher w/ a decent northbridge heatsink). When in doubt search Google.

7) Increase your system FSB to 10-15mhz above it’s rated speed. Always make sure your PCI bus speed isn’t too high before you SAVE and exit your BIOS.

8) Then see if you can boot into your operating system. If your computer boots into your OS, and doesn’t restart, or lock-up, increase the FSB by another 10-15mhz.

9) Continue until your computer reboots unexpectedly, or locks-up. When this happens go back into your BIOS and lower your FSB by maybe 5mhz and try again (if that doesn’t work, lower it some more).

10) If you tried a FSB high enough, you may not be able to get back into your BIOS to lower your settings. In this case, you have to use the jumper located near the battery and CMOS chip of your motherboard. Move the jumper from its current pins, to the only other possible position. Then after about 5 seconds, move it back to it’s original location. If you don’t have one of these jumpers, take out your battery for 1 hour or so and then put it back in. You will now be back at default settings. So you must reset everything to where you were just before you hit trouble.

11) Once you are back into your OS open prime95 (which you have already downloaded and installed from here). Then start the “torture test.” This will test your system for stability. Since we’re only testing out the mobo, once torture test has ran continuously for 4 hours with zero errors/reboots/lock-ups, your FSB is stable. If you get an error or crash, lower your FSB by 1mhz or 2mhz. When running the torture test, check your CPU's temperature. It shouldn’t be above 45C MAX since you lowered your multiplier and is probably running below stock clock speed. As mentioned earlier use a program like MotherBoard Monitor to monitor your uhh... motherboard.

12) You now know and can now write down your motherboard’s max FSB

Finding your memory’s max FSB:
1) Go back into your BIOS.

2) Change your CPU/memory ratio to 1:1 (A.K.A.: 1, 1/1, 3/3. 4/4, 5/5, etc).

3) Increase your memory voltage to the max your willing to run it at (SAFE: 2.7v; MAX: 3.1v).

4) Adjust your memory timings to 2.0-2-2-6 (The last value is up to you. 5-8 should be good, but many nforceII motherboards run better when the last value is 11).

5) First, try your memory’s stock FSB. You should try your stock speed first because 2.0-2-2-x might be lower than your memory’s recommended timings. Then continue to find your memory’s max FSB just like you did w/ the mobo. Now if you work your way back up to your mobo’s max FSB, and your system is stable, then you know your memory can do a higher FSB than your mobo; but you won’t be able to find out what that is with out a higher clocking mobo.

6) The best memory stability testing program is Memtest86. You should unzip the downloaded file to a floppy/CD, then boot to that floppy/CD in order to start the test. Prime95 will also test your memory. Use both if you wish.

7) Now you have found your memory’s max FSB w/ the memory timings 2.0-2-2-x. Test your bandwidth using SiSoftware Sandra’s “Memory Bandwidth Benchmark.” Depending on a lot of factors, you may have better overall performance w/ the timings 2.0-3-3-x. (or higher). You should definitely be able to reach a higher FSB w/ these timings than you did w/ 2.0-2-2-x. So set your memory timings to 2.0-3-3 and test some more! Once you find this max FSB, test your bandwidth again w/ SiSoftware Sandra, and see which settings yielded the higher score. You can continue to test 2.0-3-2-x, 2.0-2-3-x and whatever other timings you want, or settle on using the one you have already found to work the best thus far.

Finding your max CPU clock speed:
Before we continue, I must say that the important thing is to find the best multi and FSB combination, not necessarily the highest CPU clock speed. Though it is nice to know what the max clock speed is for your chip/cooling. The best combo will depending on which program(s) you want your system to run better on. For your final overclock settings you want your FSB and CPU clock speed to be as close to their maximums as possible. A system running at 230mhz x 10 = 2300mhz might perform similar to the same system at 210mhz x 11.5 = 2415mhz. You lost 20mhz FSB but gained 115mhz clock speed. Which one is better depends on whether you’re running a CPU intensive application or a “system” intensive application. This is similar to when we found the best memory timing and memory FSB combination. To find out which combo works better: Use a program to benchmark your system such as 3DMark01 SE, or playing a game while monitoring your frames per second (FPS). Note: the following instructions assume you have found your mobo and memory max FSB. To get started w/ the CPU:

1) Enter your BIOS yet again. Set your FSB to something around 40mhz below your mobo’s/memory’s max FSB.

2) Go into the “monitoring” section of your BIOS. See what the vcc/vcore reading is when your vcc voltage is set to “auto.” Depending on the quality of your power supply, the reading may be slightly under what it’s suppose to be. But from this reading you should be able to tell your stock voltage.

3) You can then either first find your max overclock w/ stock voltage, or you can up your voltage right away to find your max stable clock speed for that given voltage. When overclocking you should never allow your CPU to get above 55C (not above 48C is better), nor increase your voltage by more than 25% from its normal voltage (when using air cooling). Feel free to play around w/ higher voltages (25%-32%) for very short term usage. But for daily use, 25% is pushing it.

4) After deciding/setting your voltage, increase your multiplier one setting. Save and exit BIOS.

5) See if you can boot into your OS. If so, continue increasing the multi by one setting, until you cannot get into your OS. Once you can’t, lower the multi back a setting. Then run Prime95's torture test. If you get an error/crash while Prime95ing lower your FSB some and try again. If you pass for 12hours or more, increase your FSB. You should now be close to your maximum clock speed. Now to consider your overclock 100% stable, you should be able to run the torture test w/ out any errors/reboots/lock-ups for 12-24hours.

6) Now find your best FSB/multiplier combination and your set! Congrats on the overclock! Now go upgrade whatever is slowing you down, and do it again! The nice thing about finding all your max speeds is that if you upgrade say your memory, you already know what your motherboard and CPU can do.

Final Thoughts
Now that you've hit your CPU wall I should tell you that your power supply (PSU) can also limit your overclock as well. If your CPU's voltage is fluctuating alot, your CPU will not be stable. Your vcore fluctuates because your power supply either dosn't have enough power to keep it at the desired level or is too poorly made to keep your voltages at the that level despite how much power it can output. That is why it is important for overclockers to buy good PSUs. To see if your PSU might be the problem, go into your BIOS or use Motherboard Monitor to keep an eye on the voltages. Vcore shouldn't range by more than say 0.07v. Your 3.3v, 5v, and 12v shouldn't jump all over the place or be under/over their ideal voltage by more than 2%-3% MAX. BIOS readings aren't always accurate. To test your 5v and 12v lines, test a molex connector using a multimeter. Need more info? Haven't you learned already... Google.com!!