Skip to main content

Overclocking Guide

Overclocking The Intel Pentium

Intel's Pentium processor is the most successful CPU ever. Because of that it has to come first here. The nice thing about this CPU is that it is also the most overclockable CPU ever. This can be attributed to Intel's increased quality demands put in place after the floating-point flaw disaster. The new Pentium MMX is just as overclockable as the Pentium Classic, maybe even better. This CPU normally runs at 2.8V. Most motherboards that offer this voltage also offer 2.9 or 2.93V. This is only 0.1 V more than 2.8 V and probably just the right thing for overclock-unwilling Pentium MMX CPUs. My own Pentium MMX 200 runs fine with 2.8 V at 208/83 and 225/75 MHz. For 250/83 I have to increase the voltage to 2.9 V and everything works fine. BTW mine's a 'SL23S'.

Please let me put a short note about the so much feared 'overclock protection' from Intel. So far the only thing Intel has done once was disabling the CPU pin 'BF1', which is responsible for the multiplier settings x2.5 and x3. My survey could reveal, that the affected CPUs are about 50% of the 'SY022' and maybe 10% of the 'SU073', both P133 CPUs. You still can run those P133 at 166 MHz, but only with 83 MHz bus speed.

Now since the message about thousands of remarked or counterfeit Pentium CPUs has eventually reached the US, Intel has to at least make some announcements to this counterfeit and overclock protection again, which they did. However already 2 years back, Intel was claiming to soon ship their chips with a overclock protection, which never took place. I still doubt that Intel will invest any money in producing this feature at all. Before they do that, they should and will have to do something against the remarking opportunity of their chips. Hence I wouldn't worry at all. Intel will probably never avoid that their chips can be clocked higher, but they may push the motherboard industry to produce motherboards that don't offer any overclocking abilities.

If you've read all the paragraphs above, you'll remember the following things:

  • Always try to increase the bus speed first if you can.
  • Don't increase the multiplier while decreasing the bus speed - you won't gain anything.
  • Try higher voltages and don't be afraid of it!
  • Avoid the P133 'SY022' and 'SU073' if you can.
  • Don't buy a remarked Pentium - there are loads of them around!

The most overclockable Pentium CPUs:

  • P150 is the absolute winner - it's most likely nothing else than a P166 in disguise!
  • P166 Classic & MMX (and hence the P150) is super for 187.5 @ 2.5 x 75 MHz and in most term runs fine at 200 @ 3 x 66 MHz.
  • P133 great for 150 @ 2 x 75 MHz or 166 @ 2 x 83 MHz - forget about higher multiplier settings with that CPU.
  • P75 most of them run at least flawlessly at 90 @ 1.5 x 60 MHz, many of them at 100 @ 1.5 x 66 MHz.
  • P200 Classic & MMX superb at 208 @ 2.5 x 83 MHz, great at 225 @ 3 x 75 MHz, amazing at 250 @ 83 MHz - the CPU for the real speed freaks!

Where do you want to overclock today?

Pentium at1st choice2nd choice3rd choice4th choice
75 MHz112.5 MHz @ 1.5 x 75 MHz100 MHz @ 1.5 x 66 MHz90 MHz @ 1.5 x 60 MHz83 MHz @ 1.5 x 55 MHz
90 MHz125 MHz @ 1.5 x 83 MHz112.5 MHz @ 1.5 x 75 MHz100 MHz @ 1.5 x 66 MHz
100 MHz125 MHz @ 1.5 x 83 MHz112.5 MHz @ 1.5 x 75 MHz
120 MHz125 MHz @ 1.5 x 83 MHz133 MHz @ 2 x 66 MHz112.5 MHz @ 1.5 x 75 MHz
133 MHz166 MHz @ 2 x 83 MHz150 MHz @ 2 x 75 MHz166 MHz @ 2.5 x 66 MHz
150 MHz166 MHz @ 2 x 83 MHz187.5 MHz @ 2.5 x 75 MHz200 MHz @ 3 x 66 MHz150 MHz @ 2 x 75 MHz
166 MHz208 MHz @ 2.5 x 83 MHz166 MHz @ 2 x 83 MHz187.5 MHz @ 2.5 x 75 MHz200 MHz @ 3 x 66 MHz
166 MHz MMX266 MHz @ 3.5 x 75 MHz250 MHz @ 3 x 83 MHz225 MHz @ 3 x 75 MHz208 MHz @ 2.5 x 83 MHz
200 MHz250 MHz @ 3 x 83 MHz225 MHz @ 3 x 75 MHz208 MHz @ 2.5 x 83 MHz
200 MHz MMX290 MHz @ 3.5 x 83 MHz266 MHz @ 3.5 x 75 MHz250 MHz @ 3 x 83 MHz225 MHz @ 3 x 75 MHz
233 MHz MMX290 MHz @ 3.5 x 83 MHz266 MHz @ 3.5 x 75 MHz250 MHz @ 3 x 83 MHz

To get a P166 running at 208 MHz is a tough thing and requires high quality hardware - I hope I'll succeed with SDRAM and the R-534, if I ever should receive it.

There is no excuse for running a P150 at 2.5 x 60 MHz as intended - this CPU definitely runs at least at 166 @ 2.5 x 66 MHz or 150 @ 2 x 75 MHz, which is even better!!

  • alzheimerz
    Wow! History..
  • I started reading it and got to " Pentium 120 to a Pentium 133." and realised the article is 13 years old, amazing!
  • mewithsfi
    quotemsg=1553,1,1]What is overclocking? Why? Why not? Is overclocking immoral? Requirements, Goals, Techniques of overclocking. How can I find out, which bus speed my motherboard supports? Special Precautions for 75 and 83 MHz Bus Speed. Overclocking the Intel Pentium. Overclocking the Intel Pentium Pro. Overclocking the Cyrix/IBM 6x86. Overclocking the AMD K5. Overclocking Step by Step.

    Overclocking Guide : Read more
    Even though this article is 14 years old the basics are still the basics. Technology has changed alot since this post. Talking about a trip down memory lane. Thanks Tom

    Overclocking to the EXTREME
  • overclocking generates a lot of heat, .i think that when you overclocked that processor it will cause a damage to mobo, because some of the pentium pro processor doesn't require heat sink?
  • Great article
  • mHonfy
    Yes, great Article! I still have my Pentium MMX 166Mhz @ 233Mhz in a Packard Bell Legend Tower Computer.
    As far as I remember, there were 2 types of P1 166MMX processors. Only special types could be overclocked. Easy 233Mhz from 166Mhz.
    Ages ago, when I got my 166MMX I swapped it to another one, and changed the jumper setting on my motherboard. My PC still runes @233Mhz. There is no heat generated although I applied a small fan over the silent heatsink. Good times! :)