Doing a little match shows I need to run my bus at 150Mhz in order to overclock the 550E to 825Mhz. The first problem with running at 150Mhz FSB is PC-100 RAM can't do that and most PC-133 RAM can't do it either.  A quick phone call to Corsair fixed that problem. Corsair sent over a 128 Meg strip of their PC-133 SDRAM that they swear to me will run at 150Mhz.

With the RAM problem out of the way it was time to chose a motherboard for LAN 825. I went with the new Abit VT6X4 for the following reasons:

• It's made by Abit

• It can accommodate big heatsinks

• It has a 1/2 AGP divider

• It has a 1/4 PCI divider

• It can run RAM speed independant of FSB speed

• It has AGP 4X

The Abit VT6X4 is based on the new VIA 133A chipset. The main reason for going with this board is the 1/2 AGP divider. BX chipset motherboards like the BE6-II uses a 2/3 AGP divider.

AGP video cards like the Creative Annihilator Pro is meant to run on a 66Mhz AGP bus. When running your system on the stock 100Mhz FSB the AGP bus runs at 2/3 of that speed (66Mhz). The problem comes when you increase the FSB. By going to 150Mhz, the AGP bus increases to 100Mhz (2/3 of 150 = 100Mhz). A 100Mhz AGP bus is way too high for my GeForce video card. However using that 1/2 AGP divider of the VT4X4 gives me an AGP bus speed of 75Mhz (1/2 of 150 = 75Mhz). This is well within the operating limits of every AGP video card. That fixes the video card problem at 150Mhz FSB.

The other nice feature the VT6X4 has is the ability to increase or decrease the RAM speed by 33Mhz. This little feature could be the difference between a stable overclock and failure. Seeing that most PC-133 RAM can't handle a 150Mhz bus speed, all you need to do is go into the Abit BIOS and reduce the RAM speed by 33Mhz. Now the RAM is running at just 117Mhz, no problem for PC133 RAM or even good quality PC-100 RAM.   Since Corsair assured me that their PC-133 will work at 150Mhz I didn't have to worry about this part.

All the PCI devices used for LAN 825 has no problems working with a 150Mhz FSB. When using this high a bus speed, the Abit VT6X4 divides the PCI bus by 1/4, lowering it down to 37.5Mhz. That's just a bit over the stock PCI speed of 33Mhz. Nearly all PCI devices will work at 37.5Mhz.

Next page: Keeping your cool

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