Coppermine Overclocking and AGP Speeds

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So you want to overclock a Coppermine?

A lot of people are trying to overclock the 500E Coppermine using BX boards now, and probably many more will try after Intel’s next round of price cuts.

You have three major issues to contend with on a BX board.

PCI Speed: PCI components are made to run at 33Mhz. On a standard BX board setup; the motherboard runs these devices at 33Mhz by dividing the bus speed by 3 – e.g. 100Mhz/3 = 33Mhz.

If you run your motherboard a little faster than 100Mhz, you are effectively overclocking your PCI devices. So if you are running at 112Mhz, your PCI devices are running at 112Mhz/3= 37.5Mhz. Most PCI devices don’t mind this at all, but some do. For instance, Maxtor hard drives generally do not like this at all and often trash themselves complaining about it.

The more you go above 37.5Mhz, the more likely it is some PCI device is not going to like it. If you get PCI running over 40Mhz, most systems (not all) will not like it; so don’t be surprised if the machine doesn’t work, or gives you Registry errors, or the hard drive scrambles itself. Put it up to 44Mhz or more, and you are cruising for a bruising.

The later BX boards generally allow you to change the divisor from /3 to /4. If you are trying to run at 133Mhz with the PCI divisor set at /4, your PCI devices are running at 133Mhz/4= 33Mhz, just the speed they are supposed to run. This is much better than 133Mhz/3= 44Mhz.

Even at 150Mhz FSB If you like your equipment at all, you will always set the PCI divisor to /4 if your motherboard will let you do so. On some BX boards, you have to look carefully at the FSB settings, because sometimes it will let you run at the same speed at /3 and at /4. Or, like the BE6-II, there is a separate setting (PCI Clock/CPU FSB Clock) for you to do so, so make sure you set it to 1/4.

AGP Speed: This gets a lot more complicated than PCI, but here’s what you need to know for a BX board:

1) AGP is designed to run at 66Mhz. On a BX board, you either run it at a 1/1 ratio with your bus speed, or at a 2/3 ratio. There are no other settings, nor will there ever be any other settings.

2) AGP 2X does not mean AGP is running twice as fast as AGP 1X. All it means is that there are two channels working at the same time rather than one. (With AGP 4X, there are four channels.)***

3) If you are running at 133Mhz with an AGP setting of 2/3, you are running the AGP transfer rate at 89Mhz. At 150Mhz, you are running a transfer rate of 100Mhz. This is a lot higher than 66Mhz.

4) From everything I have seen so far, you are NOT overclocking the video card itself the way you would overclock the CPU or PCI devices. If you were, performance would get a lot better as you pushed up the AGP speed, but it doesn’t. Video cards have their own clocks; that’s why you have to tweak them upward. What you are overclocking is the transfer rate to the CPU.

5) Just because you set your BIOS to AGP 2X doesn’t mean your machine is running at 2X. The AGP standard provides for the video card and motherboard negotiating what speed AGP can run during bootup. If that feature is implemented in your video card/motherboard, if it can run at AGP 2X, it will. If it can’t, it will go back to AGP 1X if it can, and it won’t tell you that it did.

6) This is just what is happening with a lot of video cards. The Matrox G200/G400 will automatically do this. I’m not certain about the NVidia cards, but I think that’s what happening. The new BIOS setting on the BE6-II makes this happen, as does the Powerstrip tweak recently mentioned.

7) So it looks like the issue really is “Can your video card shift into AGP 1X mode by hook or by crook, and if so, can it transfer data fast enough using AGP 1X?”

To answer that for sure, I need your help.

If you are successfully running an AGP card with a bus speed higher than 124MHz (and especially at 140Mhz or more); I’d appreciate it if you did the following:

1) Download SiSoft Sandra Standard HERE, if you don’t already have it.
2) Once it’s installed, run the Mainboard information test.
3) Once you do that, send me an Email with the following information:

  • Processor and bus speed
  • Video card used
  • Motherboard (and if Abit BE6-II, AGP setting)
  • AGP/CLK ratio

Include the following information from the Mainboard information test:

  • Bus Speed
  • Current Data Transfer Rate
  • Sideband Enabled
  • Anything you did to your system that got it working at that speed.

If you have tried and can’t get an AGP card to run with a bus speed higher than 124Mhz, please send me the following:

  • Processor and bus speed
  • Video card used
  • Motherboard (and if Abit BE6-II, AGP setting)
  • AGP/CLK ratio
  • What you tried to do to get your system working.

Once we get this information, we can see whether or not what I’m saying is correct, and what people can do to get their BX boards running that quickly. I know some people have reported luck with disabling sideband and reducing aperture size, hopefully, this little questionnaire will give us more info on that.

Disclaimer: We don’t know whether this is safe in the long term or not; it may well not be. We make no claim that it is, and if you choose to do this, that’s solely your responsibility.

This is at best a temporary expedient until suitable motherboards are available which will run AGP at lower, safer rates. Besides, why buy an AGP 4X video card when you can only run it at 1X? You’ll want (and eventually need) a motherboard with AGP 4X to keep up with other fraggers.

Memory: While some PC100 memory can run a lot faster than 100Mhz; don’t expect miracles at 150Mhz. Current PC133 memory is getting pushed at 150Mhz. You should check Deja to see if people using your memory have had luck running it at very high speeds, but even if someone has, memory chips differ, so it’s not a guarantee.

Wait for the Coppermine-128s? If your equipment can’t quite handle 150Mhz; there is no need to fret or stop feeding your children to free up cash for the next upgrade. By the end of March, the first Coppermine-128, or “Celeron–The Next Generation” should be out.

I think there is a very good chance you’ll be able to overclock those to 800 or 850Mhz running at a 100Mhz bus. It probably won’t be quite as fast as the regular Coppermines, but it will be close enough, and you’ll get most of the improvement and still use your current equipment without stressing it out. That may be the wisest solution for a lot of people.

***Actually, there are more than two/four channels in play. The additional channels are what are referred to as “sideband.” What sideband does is allow instructions to be processed faster. Other mechanisms allow main memory to be used for AGP textures.


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