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Many Qs conserning CPU upgrading and FBSs (NOT "what should I get")


I'm looking to update my CPU from an [AMD Duron, 1.1 GHz, L1-128kB, L2-64kB, 200 FSB] to a [AMD Athlon XP 2800+, 2.086 GHz, L1-128kB, L2-512kB, 333 FSB]

My first question is, can a CPU with a 333 FSB run on my motherboard at the supported FBS? I have the SiS730S chipset. My motherboard user manual says it supports 100/133 MHz FSB, but Sandra 2004 says "Front Side Bus Speed: 2x 100MHz (200MHz data rate)". Also, are there any other limits I should be aware of?

Later on I plan on getting a new mother board that matches the 333 MHz FBS. How much of a performance increase would that theroticly bring me? Not counting lantency and other odd variables. Is it as simple as: 333/200=1.665 or '66.5% Performance Increase'?

While looking at diffrent motherboards some say DDR, SDRAM, and some say DDR-SDRAM. So I'm confused as to if there are motherboards that support both, or if possibly, any mobo that supports DDR is backwards compatible and can also handle SDRAM. It'd be eaiser to update the mobo then the RAM to DDR later on and use my current SDRAM untill then.

Well, day after christmas I plan on melting down $100 and pouring it into my computer one way or another. I know currently my biggest bottleneck is probbly my memory, but I'd have to update my mobo before that anyway. One final question, how can I find out the FSB of my memory (256 and 128 SDRAM) without opening up my computer and pulling out the chips?

Any help or links to good information, or even just personall opinions is greatly accepted. Thanks for reading and everyone have a Merry Xmas here soon. 1 more day of work then a 3 day weekend, yay! :)


New member
Your mobo has a double-pumped bus, so at 100/133 MHz it has an effective speed of 200/266 MHz, depending on your exact settings. The AthlonXP you're considering might work in that mobo, but if it does the speed will be much slower than advertised, about 1.66 GHz at best. To take full advantage you'll need a mobo that supports a 166 MHz FSB (333 effective). The performance increase from the extra bandwidth can't be measured so easily as you describe. Best to search some comparison charts at the myriad hardware sites and see the differences across a wide spectrum of applications.


DDR-SDRAM and plain SDRAM are not pin-compatible. Some mobos do support both (some SiS models I believe), but in seperate slots and not at the same time.
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-= Clark Kent -X- =-
You'd do well to check and see if your current motherboard supports the new CPU first. Maybe a bios update may enable support for it, but as said above, the cpu will be underclocked on your board. Sdram is a serious bottleneck for the newer Higher clocked FSB athlons.

The performance difference between a 266 mhz FSB and a 333 mhz FSB is around 10 - 20%. Not much but noticable. It will be more noticable in bandwidth hungry applications. (divx/mp3 encoding). Even with those FSB speeds though, SDram will limit the performance of the Athlons since sdram is limited to 100/133 mhz.

I've overclocked my barton 2800+ 333mhz FSB to 400 mhz FSB. ;)


dont bother. it's not worth it. instead by a new nforce 2 motherboard of some kind, and either the barton 2500+ or tbred 1700+/1800+ and overclock them. I can garuntee you'll get more for your money.