Setting "CPU Frequency" in BIOS


Jan 18, 2005
Hello, I've got a noob question for you folks: I just got a new motherboard (PCChips m848A), which says it supports up to 400mhz FSB. I have two PC400 DIMMS in it. When I booted the system and went to "Advanced Chipset Setup" in the BIOS, I noticed that the "CPU Frequency", which I assume refers to the FSB, defaults to 200 and that the "CPU/DRAM Clock Ratio" is set to 1:1, making the RAM run at 200mhz as well.

There is an option to change CPU freq detection from "Auto" to "Manual", but before I do that and change the CPU freq to 400 I want to be sure that I'm not just confusing myself and that I'm not actually about to break something.

Any advice about what to do here would be greatly appreciated!



I'm glad you asked. There isn't really a 400mhz fsb. It's a question of pr speak. Your mobo may be showing pr speak, in which case, the fsb would really be 100 mhz. As to what you need to set it to , that depends on your chip.
Most semprons, and bartons use a 166/333 fsb. Some of the newer xp3000s use a 200/400 fsb, as do most of the xp3200s. Let us know what chip you have, and we will tell you how to set the fsb.


Actually, your board has an auto detect for chip frequency, on that same bios page, at the top. If it already says DETECT CPU FREQUENCY and AUTO, that means you have a 200mhz fsb chip. It operates at an equivalent speed to 400mhz because it works twice per clock cycle (once on the rising edge, once on the trailing edge)
To simplify, if on that bios page, it says auto, after detect cpu frequency, you are good to go. If it does not say auto, hit the + sign until it does.


Former Staff
Yes, 200MHz clock rate provides 400MHz data rate. When they said 400MHz, they were refering to the data rate. That's because big numbers sell better.

So you got your 400MHz, be happy, and have a nice day.