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Overclocking Guide

Special Precautions For 75 And 83 MHz Bus Speed

Using this higher bus speeds includes some important restrictions which you should be aware of.

  • The PCI bus runs at 37.5 or even 41.6 MHz. This can lead to several problems with PCI devices. Typical trouble makers are SCSI controllers, some video cards, and network cards. SCSI controllers and network cards often refuse to work at the faster speed, but some video boards just get much hotter than usual. If you find a way to cool these video cards, you shouldn't have any trouble. My Diamond Stealth 64 Video VRAM isn't affected at all by those higher bus speeds. I hope the 75/83 MHz bus speed survey will help us find out which PCI devices run at higher PCI bus speeds.
  • The speed of the EIDE interface included with the chipset is not only determined by the PIO or DMA modes, but is also highly dependent on the PCI clock. This is one reason why the EIDE interface is always slower in systems with 60 MHz bus speed or less. This is also valid in the other direction, meaning your interface will be faster when you are running at 75 or 83 MHz bus speeds than at 66 MHz. At first this sounds fine, but often either the interface or, in more cases, the hard disk isn't up to the faster bus speeds. My HDDs work fine at 75 MHz bus speed, but at 83 MHz I have to reduce the PIO down to 2. The same is valid for EIDE CD-ROM drives. This could be the cause if you are running into strange lock-ups in windows.
  • The Asus P/I-P55T2P4 is one example of a board that does not allow you to adjust the ISA bus speed. It seems to be a fixed divider from the PCI clock. This can cause sound cards to run into trouble if they don't like the higher ISA bus speed. I haven't come across this problem myself yet, but I've heard of one fellow whose AWE 32 produced strange sounds when running at a faster speed. If you run into this, increase the ISA wait states in the BIOS setup to try to remedy the problem.
  • Let me say again that the RAM type and quality is of great importance. Most 60ns EDO will run fine at 75 MHz bus speed, but for 83 MHz you'll need high-end EDO or SDRAM (as long as the motherboard supports it).
  • 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! :)