FSB, system bus, school bus, bus boy, TOO MANY BUSES

[Leageth]

I'm not exatly stupid when it comes to computers, but this is the first time I'm attempting to build my own. I have 2 setups layed out, an intel and an amd based. Since this will be my gaming rig I'll most likely go with the AMD Athlon 64 due to its superior benchmarks for gaming. But I'm having trouble picking out the right hardware. I just don't understand buses. The Athlon 3200+ I'm looking at is 1600 bus speed, but why? its going to be limited by the 800 FSB on the mobo isn't it? And with a 800 FSB I can get DDR400 before FSB starts limiting the RAM speed right?


Basically can someone explain to me the realations between the buses on the CPU, mobo, and RAM?

[Tin]

the A64 is a great processor, and very well worth the money IMO. which video card do you plan on getting? if youre going to swing the cash for an A64, you might as well lay some down for a swank card, like a 6800GT. do you plan on purchasing a socket 754 CPU or a socket 939?

[Leageth]

I'm sticking with my 9600xt, performs almost as well as my firends 9800 when overclocked. Going with the 754 socket cause of cheaper price, the 3500 and 3800 with the 939 and the fx's with the 940 are outta my price range, but I might consider a 3400.

Can anyone answer my questions about the buses? I just don't understand the relation between the FSB, processor and RAM. Does FSB have to a certain speed to not limit the cpu? And the FSB has to be atleast 800 to handle DDR400 right?

[Tin]

if youre going for a 3400+, you might as well get a 3000+ and get a better video card . the processor doesnt have much to do with games. the video card plays the most important role. that $150 youd be saving would be great towards a 6800GT. a 9600XT is 4 piped, a 6800GT has 16-pipes, thus you can play at higher resolutions with all of the eyecandy you want. if youre going to buy tomorrows CPU, why buy yesterdays video card to go with it ?

[RedKangaroo]

Correct me if I'm wrong, but I don't think a FSB really limits the CPU, but rather controls the speed of the CPU. So a FSB that's meant for a specific CPU is already at the right speed to handle it. Actually with the Athlon64, the FSB is integrated into the chip, so whatever it is, it's meant to run at that speed. I have a feeling that DDR400 (PC3200) is the right speed for it, but if you plan on doing overclocking, it would never hurt to go for a little higher speed (besides the extra money.) Although it might be better to go for higher quality than more speed.

[chzlchp]

You think YOU'RE chip challenged!? I've got a good link that will help, but I actually gotta talk you down into it. That's how un-schooled I am on this stuff. But here goes. About 7 threads below yours, I started a thread called, "Is FSB the mob Bus Clock?" earlier this afternoon. Go into that thread and go to the 5th entry, offered by "WhatsThisBoxFor?", who gave me an incredible link that is a matrix chart of all the current CPU,s, and what their tech stats are. Go there, find that, and I hope that, like me, you end the day a lot more knowledgeable than you began it, thanks to some really savvy and helpful people who wander these halls.

[Spartan]

A bus is just the connection between components in a computer. There are basically 2 types of buses. Internal buses connect internal components (like your video card) while external buses connect things like printers. Bus speeds are measured in bits per second or in megabytes pers second. Front Side Bus is the connection from the CPU to RAM. The bus speed for your AGP and PCI slots is dependent on how fast the FSB is. Yes it is important to match your RAM with the FSB. If you use RAM that is slower than what the FSB is capable of handling then it will bottleneck performance and the machine will not run as fast as it could. If you use RAM that is faster than what the FSB can handle then the FSB will run at it's max, but not at the full potential of the faster RAM that you have. Both situations will result in a useable computer but they are not ideal matches in terms of efficiency (and maybe dollars spent).

-Spartan

[Yuanji]

doesn't buying faster ram allow for overclocking though?

[Leageth]

Originally Posted by Spartan Front Side Bus is the connection from the CPU to RAM. The bus speed for your AGP and PCI slots is dependent on how fast the FSB is. Yes it is important to match your RAM with the FSB. -Spartan

but the bus on the cpu runs at 1600, and the FSB is 800 on most high end boards, so wouldn't the cpu's potential be bottlenecked even if the ram's isn't?

[Yuanji]

no.. i think the internal FSB on the Athlon 64 is 400. it doesnt have quad pumping like the p4s

[Spartan]

As far as I know the top FSB is still 800. Yes to properly OC you would need faster memory. I'm no expert on the new AMD stuff but I think AMD has Hypertransport which allows a 800 FSB.

-Spartan

[ric449]

Hypertransport doesn't connect to memory, it connects to the southbridge. You still have the same old 400MHz FSB, except the controller circuitry is now built into the processor.