system bus speed

Can someone answer for me, why a motherboard sometimes supports more than one system bus speed? Under what circumstances.

Thank you.

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  1. *Correct me if I'm wrong, I'm really not sure what I'm saying lol*

    I think a mobo supports both 100mhz and 133mhz bus speed. Then, according to the processor being used, this bus multiplies. I also think RAM takes a share here, if you're going to use a processor that has 1000mhz FSB , but you have DDR333 RAM, then the overall bus decreases to 800mhz

    *Omg that turned out terrible! someone! please correct me lol*
  2. hmmm....thank you for responding to my question, but could you explain alittle further? I still don't understand under what circumstances a motherboard would (or would want to?) support more than one bus speed. Is it to increase performance? Probably...but why increase performance this way over another way, like more Ram or something. And what is a mobo?

    I'm taking a hardware class and although interesting, this stuff boggles the mind.

    Thank you again for your time.

  3. because one motherboard can use different revision of the same CPU. Like the socket A CPU. first, they were running a 100 MHz FSB.. then 133..and 166.. and then 200MHz. The later board that support the 200 MHZ cpu can be slowed down to support the old 100MHz FSB CPU. So, if the board you buy in 2000 just died yesterday, and would be looking for another one today. You'll likely have to get a 200MHz version and make it run at 100MHz to support your CPU. Same is true for memory that went from PC1600 (DDR200) to PC3200(DDR400) or AGP 1x that went up to 8x. But be warned that some motherboard do not support all the voltage range that AGP went thru, so a 8x AGP might not be able to run a 1x agp card and vice versa.
  4. Yup, it's pretty much like that. Motherboard (mobo) makers can't tell which exact processor you're going to use, like Socket 939 motherboards, they support the AMD 64, but also the AMD 64 X2 series and some AMD FX series. That's why they need to be 'compatible' with whatever processor the owner is planing on using that'll fit the socket. Then the motherboard will either work at full speed, or 'downgrade' to meet the CPU's bus.
  5. thank you for your explanation, that helps :D
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