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Overclocking Guide

Overclocking The Cyrix/IBM 6x86

I have mixed feelings about writing this paragraph. One one hand, I promised you information on this subject ages ago, but on the other hand, much of the information regarding the 6x86 M1 and the upcoming M2 is about to change. Nevertheless, I will refer to the good old, well known 6x86 and it's later stepping versions.

Due to the massive heat production of the older versions (steppings of less than 2.7) and the overly high heat production of even the latest versions, this CPU is not as flexible as the Pentium for overclocking. The first important thing to remember is that you are indeed able to kill your 6x86 with overclocking. I've never heard of an Intel CPU with this problem, not even a 486, but I have heard several stories of fried 6x86 CPUs. Hence I DO NOT recommend you overclock this CPU at all. The only reason I don't refrain from writing about the 6x86 is that I've been promising this information for a long time.

Overclocking the 6x86 is quite a bit more restrictive than overclocking a Pentium. This is mainly due to its heat production but also can be attributed to it's limited multiplier settings of x2 and x3. You can more or less forget about the x3 multiplier because the only scenario where it makes sense to use it is at 3 x 50 MHz. Due to the pathetically low bus speed, this is completely uninteresting in the way of performance. Hence this only leaves the x2 multiplier.

If you really want to overclock your 6x86, think small! Think in small steps!! It is worth considering just one step up. This means P120+ (100 MHz) to P133+ (110 MHz), P133+ (110 MHz) to P150+ (120 MHz) and P150+ (120 MHz) to P166+ (133 MHz). The step from the P166+ (133 MHz) to P200+ (150 MHz) seems to be too big and has a fairly low success rate with quite a high risk of losing the CPU.

You'll achieve the highest success rate with 2.7 or 3.7 stepping 6x86 CPUs because they run more stable and produce less heat.

Cooling is paramount for the overclocking of a 6x86, so don't even think about overclocking this CPU without a HUGE heat sink or a power peltier.

I hope all this will all change with the release of the split voltage 6x86. This chip will be run at 2.8 V and should result in much less heat production. Maybe the 6x86 will suddenly turn into a really great overclocking CPU.

  • 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! :)