Overclocking PC Hardware:
What is Overclocking: |
WARNING! |
What is Overclocking: |
WARNING! |
First, be warned that overclocking may greatly increase the operating temperature, and reduce the useful lifespan, of the hardware in question, and thus increase the risk of damaging it! I take no responsibility for damaged hardware due to overclocking by following my instructions on this page. You follow these instruction at your own risk! Although having said that, I have successfully overclocked many CPU's and graphics cards, and none have been damaged to my knowledge? If you are sensible and follow the instructions carefully, the odds are on your side.
All hardware runs at a set speed (set by the manufacturer) and some hardware, such as processors and 3Dfx graphics cards and motherboards, can be overclocked, this results in higher performance on the same chip. The increased speed also increases heat. By adding extra cooling at the same time as overclocking, you can greatly reduce the chances of the hardware overheating. You can also combat heat by adjusting the M/B voltage settings. The makers set these relatively low speeds to ensure the hardware passes all the relevant performance tests during the manufacturing process. If they set the hardware at its maximum speed, more would fail at the higher speed. By being conservative in the setting of hardware speed, they guarantee more pieces of hardware pass the process. Its this extra built-in speed that overclockers try to take advantage of.
By overclocking your hardware you are gaining a performance increase, free of charge! You can gain as much as 15 or 20% which, in computing terms, is an enormous gain? The golden rule in overclocking is to take small steps. Do not try to increase your CPU speed by 20% straight away, try just one incremental increase at first, then test the CPU for a couple of days. If it appears to work ok, try the next logical increase, and see if that works. keep increasing, and testing, until the CPU doesn't work or you see no further gains. Then go back one increment and that should be the optimum setting?
You buy a Pentium 166. Why is it a 166? Its rated as 166 because the maker tested it (maybe not this exact one, but a CPU from the same batch?) to be successfully working at that speed. There is no real difference though between a 166 and a 200, or even a 233, they are the all the same basic chip. So a 166 has the potential to be a 233. All you have to do is try it and see? How? Well, two things determine the speed of a CPU. The busspeed and the multiplyer on the M/B. The busspeed times the multiplyer equals the CPU clock speed. Most older PC's used 66MHz busspeed. You change the voltage, multiplyer or the busspeed setting, by altering jumpers or small dipswitches on your PC's M/B, (Check your M/B manual or the Net for exact M/B setting details) or if you have a newer M/B by changing settings in your soft bios screen.
What happens if the PC doesn't like being overclocked or the CPU heats up too much? Well, generally the PC will just crash or lock up. In which case you simply go back a step, or go back to your default settings, and everything should work again. If your PC or CPU does run hot for prolonged periods, or you are using the wrong voltage settings, this is when you may cause serious damage to the components. Try to add extra cooling, (add one or two extra small CPU type fans to the case, most cases have spare power connecters and fan mounting points) at the same time as overclocking, and you should avoid this overheating problem.
So our 166 was a CPU running at a busspeed of 66 with a multiplyer of 2.5 Therefore 66 x 2.5 = 166: So to overclock our CPU all we need to do is change the busspeed (called overbussing) or the multiplyer on the M/B. Most M/B's allow these factors to be altered because most M/B's are designed to be used with many different CPU's. A Pentium 200 is therefore a CPU running on a busspeed of 66 at a multiplyer of 3 (66 x 3 = 200) and a 233 is running at 66 with a multiplyer of 3.5 (66 x 3.5 = 233) I run as a second PC at home an AMD K6 166 which is running with a busspeed of 75 at a multiplyer of 3 thus giving a clockspeed of 225 (75 X 3 = 225). This is actually faster than a 233!
Faster multiplyers mean faster CPU's. However, faster busspeeds mean faster PC's. Because the busspeed speeds up all the important parts of a PC, not just the CPU. Think about it.... What is connected to the busspeed? the Hard Disk, the main system Memory, the Graphics Card, all the important bits. So speed up the busspeed and everything speeds up. One thing to bear in ming here though, is that not every component in a PC likes to run on a faster bus. The Graphics card and hard disc runs at half the busspeed. Which would normally be 33MHz, but speed up the busspeed to 75 and the graphics card and hard disc are now running at 37.5! Worse still try running that same bus at 83 and the graphics card and hard disc are struggling to keep up at 41MHz!!!
Lots of people had trouble running hard disks and graphics cards at anything over 75. Some managed 83, but not many and not for long? Now that we have 100MHz busspeeds (and faster) it has made things a little easier. Hardware connected to modern busspeeds can drop their speed incrementally as needed to cope with the differences in speed. Those hard disks and graphics cards that struggled on older M/B's will now be able to run at 1/3rd the busspeed as well as at 1/2 speed. So if you run a 100MHz bus your components can happily run at 33MHz if 50 is too much for them?
As CPU's got faster, more overclocking opportunities presented themselves. The Intel Celeron CPU's were famous for their overclockability. I had as my main PC, a Celeron 300 which happily ran at 450MHz. But there are other drawbacks. Some Celerons were multiplier locked at 4.5 others at 5. My 300 would only work using multiplyers of 4.5, so my overclocking (overbussing) opportunities are narrowed to 4.5 x 66 = 300, or 4.5 x 75 = 333, or 4.5 x 83 = 375, or 4.5 x 100 = 450, or 4.5 x 112 = 500. Most people succeeded in getting 450 to work, some even got 500 working too. If I could alter the multiplyer my choices would be much greater? The Celerons locked at 5 were even worse off, offering only 5 x 66 = 333, or 5 x 75 = 375, or 5 x 84 = 415, or 5 x 100 = 500 (which almost never worked?) so people with these CPU's usually ended up running it at 415 or worse 375!
What of newer CPU's? well early Pentium 2's had some overclocking potential, but it sometimes involved very strenuous efforts for a relatively small gain. And later Pentium 2's seemed to have been locked at one speed. Pentium 3's are not very overclocking friendly either? (See below). The new AMD Athlon CPU's seem easier though? (See Athlon link at top of page).
The existing Pentium three (Deschutes P3) has the following features: .25 Micron core; 32KB L1 Cache; 512KB off-die ½ core speed L2 Cache; 100MHz Front Side Bus;
The newly proposed Pentuim three (Coppermine P3) has these features: .18 Micron core; 64KB L1 Cache; 256KB on-die full speed L2 Cache; 133MHz Front Side Bus;
What do these differences mean? Well, there will be changes to the way we overclock P3 CPUs when the Coppermine arrives, and most of the changes are positive. As the micron size is reducing this means that the cpu will not get so hot, less heat is better for overclockers! Also moving the L2 cache to on-die in the Coppermine P3s offers more potential for overclockers, as the current off-die L2 cache on the Deschutes P3s is limited as to how far you can push the cpu speed.
All Intel CPU's (P2 & P3's) are clock multiplier locked, therefore users can only manipulate the Front Side Bus or FSB speeds of their motherboards to obtain higher CPU clock speeds. Here are examples of clock multipliers for P2 and P3 CPUs:
Possible P2 - 350 multiplier - 3.5 only Possible P2 - 400 multiplier - 4.0 only Possible P2 - 450 multiplier - 4.5 only Possible P3 - 450 multiplier - 4.5 only Possible P3 - 500 multiplier - 5.0 only Possible P3 - 550 multiplier - 5.5 only Possible P3 - 600 multiplier - 6.0 only
Top:Therefore, using different busspeeds you can obtain the following cpu speeds: P3-450 overclocking options: 4.5 x 103MHz = 464MHz 4.5 x 112MHz = 504MHz 4.5 x 117MHz = 527MHz 4.5 x 124MHz = 558MHz 4.5 x 133MHz = 600MHz P3-500 overclocking options: 5.0 x 103MHz = 515MHz 5.0 x 112MHz = 560MHz 5.0 x 117MHz = 585MHz 5.0 x 124MHz = 620MHz 5.0 x 133MHz = 665MHz P3-550 overclocking options: 5.5 x 103MHz = 567MHz 5.5 x 112MHz = 616MHz 5.5 x 117MHz = 644MHz 5.5 x 124MHz = 682MHz 5.5 x 133MHz = 732MHz
NB: Some of the above examples are very difficult to achieve (especially those using 133 busspeed) and may only work with the highest quality components, eg: memory modules, and may require voltage changes, etc. As cpu and busspeeds are increased, this results in a heat build up, and heat dissipation is a must to successfully overclock. This is usually achieved via adding cooling devices (fans). Fans come in a variety of shapes and sizes, which are basically divided into two types. Case fans and CPU fans and heatsinks.
Case fans are connected to the case and can be pointed directly at components, cpu's, graphics cards, or hard disks are the usual culprits when it comes to producing lots of heat, or can be added to aid airflow through the case. If you mount one fan say at the front of the case at low level sucking in cool air, and another at the rear at high level (cos warm air rises!) blowing out air, this can dramatically affect the internal temporature of the PC components? As can leaving the case off, but it doesn't look pretty when you do this! CPU fans and heatsinks are a must even if you are not overclocking! They keep the cpu at a comfortable temporature and this helps to maintain a stable system. Luckily, P3 cpu's do not appear to get very hot, even when overclocked?
If you're aiming for a FSB speed of more than 112MHz, disconnect any non-essential parts to your pc, such as network cards, SCSI controllers, PCI Sound Cards, or any other component that runs on the PCI bus. This make it easy for you to properly diagnose any errors later. Also, change your UDMA IDE HD's mode to PIO Mode 2 or DMA Mode 1 in the bios settings. This will decrease your HD performance slightly, but will also protect your hard drive when overclocking beyond the 112MHz FSB. The reason for this is that PCI peripherals are only designed to operate at a PCI bus speed of 33MHz (1/3 of 100MHz or 1/2 of 66MHz FSB). Some PCI peripherals may not remain stable at higher FSB speeds (even just using 112MHz), and they may cause the loss of some data on the Hard Drive. Although it is very rare for thsi to happen.
If, after overclocking, your pc boots ok, counts the memory, and gives you a close or correct cpu speed (the NEW cpu speed may sometimes be incorrectly reported in the boot up screen, especially if it's a non-standard number such as 558MHz), then you're on your way to success. If the machine refuses to boot up at all, then there are probably one of two problems: incorrect voltage, or inability to achieve the settings. Regarding incorrect voltage, in the 440BX motherboard, there are only a few motherboards that allow for the manipulation of a CPU's voltage level. and if you don't have one of them, then you won't be able to manipulate your voltage.
Several problems can also occur during the loading of Win95/98. This may be due to heat problems. If your machine has booted up, and has the correct or near correct cpu speed for your overclocked CPU, and then proceeds into the Win95/98 load screen only to freeze, there are 2 things you can try. Lower the HD's PIO level one notch below what it was previously. Reduce the CPU's heat by taking the case's cover off (or adding cooling fans) and removing all non-essential PCI components. You can reduce the internal pc temporature considerably simply by taking the case cover off. To stabilize the system, many overclockers (like myself) run the pc permanently with no case cover. As long as you clean the system to remove dust, you should have no problems running your pc without a cover.
As most overclockers are aware by now, the Intel Celeron 300A was a legendary CPU. Easily capable of being clocked at 450Mhz, and sometimes up to 500Mhz! The multiplier being locked at 4.5 enabling the CPU to be easily speeded up by altering the busspeed. EG: 4.5 x 66 giving the default 300 speed, but by changing the busspeed to 100, 450Mhx was reached. (4.5 x 100 = 450). And if higher busspeeds of say, 112 were used, the magic 500Mhz could (sometimes?) be reached. (4.5 x 122 = 504Mhz)
Recently, new, faster Intel Celerons have been released, the 500A and the 533A. both appear to be as overclocking friendly as the earlier 300A. The 500A is multiplier locked at 7.5 and the 533A is locked at 8 (so you need a M/B that supports multipliers of 7.5 or 8) This means if you raise the busspeed from the normal 66 to 100 (via the softmenu BIOS screen, or jumpers or dipswitches on your M/B) you can achieve 750Mhz (7.5 x 100 = 750) or 800Mhz (8 x 100 = 800) And apparently most 500A/533A's will easily reach 750/800 without too many problems?
