The Benchmarks

As you can see, there's nearly no performance difference between PC-100 and PC-133 RAM, unless you can see the difference between less than one frame per second. Given these kind of results, there really is no reason to get PC-133 RAM over PC-100 when running at bus speed below 133Mhz.

The main reason for getting PC-133 RAM is of course, overclocking. To do the overclock test, I put the RAM into the Project 620 system (which now runs an Abit BE-6 motherboard), removed the P3-500 that was in it and replaced it with the unlocked P2-300 and set the multiplier to 2X. I'm not really trying to overclock the CPU. I'm trying to find the max bus speed the RAM would still work at.

I then discovered that my Viper Ultra would not work on 133Mhz bus. The reason for this is because the Intel BX chipset on the Abit BE6 doesn't allow a 1/2 AGP divider for the video card. You can only chose between 1 to 1 or 2/3. Setting the AGP divider to 2/3 means the AGP bus is running at 89Mhz when using the 133Mhz bus. Most AGP cards will not work at this level. What I end up doing was putting in an old 4 meg S3 Virge video card into the PCI slot. At 133Mhz bus, the PCI speed is divided by 4, which mean it's running at 33Mhz. Not problem for a PCI device. Here are the overclocking results.

The Micron PC-100 RAM was stable up to 133Mhz. This is really good for PC-100 RAM, but then again, the Micron RAM is really PC-125 RAM. The Corsair PC-133 RAM is stable at up to 140Mhz bus.

The main problem with this setup is that most AGP cards will not work at this kind of bus speed. I know the Intel i740 card can run with the AGP bus set to 100Mhz, but who in their right mind would take an i740 over a Viper Ultra? Even if the RAM can work at over 133Mhz, it's no good if your video card won't. This problem should be fix when Intel release their i820 chipset.

My conclusion is this. Good quality PC-100 RAM will be enough for most overclocked system. You should look at the CPU you're running and buy your RAM according to that. In the case of my Celeron that runs at 605Mhz, even average PC-100 RAM will do as the bus speed will only be 110Mhz (110x5.5=605Mhz).  If you are using a PIII-450 or another low multiplier CPU, then you should get high quality PC-100 or PC-133 RAM. Fellow LAN party guy, MickŪ has his PIII-450 running at 580MHz (129Mhz X 4.5) with Micron PC-100 RAM and it's 100% stable. The system will work at the 133Mhz bus but the Viper Ultra will lock the instant he fires up a 3D game.

While the Micron PC-100 and Corsair PC-133 RAM will allow you to operate at or over 133Mhz bus, it's pretty useless trying to playing Quake 3 on a S3 Virge. :-)

A month ago, I would always recommend PC-133 RAM over PC-100 RAM because the price difference was like just $5. However the gap in price is getting wider, nearly $30 now. Weather or not PC-133 is worth this extra money is up to you. If  you're thinking of future upgrades, then it's worth it, as the new i820 chipset will make full use of it. Also you have to consider that I use very high quality PC-100 RAM for this comparison. Most  PC-100 RAM will not work at 133Mhz.

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