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What's the deal with fsb and memory?

Last response: in CPUs
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August 8, 2007 3:22:55 AM

I posted this in the memory section, but I'm not sure which section it truly belongs in, seeing that it involves both the cpu and memory. So I'm reposting it in this section.

I want to buy faster memory, I currently have 400mhz. But, I was reading that memory should be equal ratio to the fsb. What is the importance of doing this? If I go by this, shouldn't I only buy 533? I was thinking of getting 800mhz, because of the higher bandwidth. But don't want to if there will be a performance decrease because it isn't running 1:1 with the fsb.

Even if I don't intend to oc, will 800mhz still give me better performance than 400 or 533? My current mobo doesn't officially support 400 or 533, but for some reason my 400mhz is working, but I'm experiencing a decrease in performance. So I don't know......

I'm so confused, what should I do? Someone please give advice. Any and all is appreciated. Thanks

(system in sig)

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August 8, 2007 4:00:40 AM

With the 1066 FSB rating it is actually running at 266MHz (which you already know) which means the lowest RAM you can run is 266MHz (DDR2 533) because the lowest a motherboard will do is a 1:1 ratio between the FSB and the RAM.
The main reason people talk about keeping the FSB and RAM at a 1:1 ratio is because it allows the most overclocking ability with the least costly RAM. Since RAM goes up very fast in price when you go above DDR2 800.

Most motherboards will run RAM from 1:1 to 1:2 compared to the FSB. There is a benifit to running RAM at faster then 1:1, but it isn't usually a big difference. There are some cases where some motherboards decreased in performance when going higher then 1:1, but I believe it was mostly only a limited chipset/manufacturer that had that problem.

For many of the OEM manufacturers they run their RAM all at 1:1 because the savings in lower speed RAM is worth more to them then the minor increase in speed from using faster RAM.
The reason enthuseasts use 1:1 is to get the most overclock out of the RAM before they have to start increasing RAM voltage and start stressing the RAM. RAM tends to not overclock nearly as much as the FSB/processor so you get faster RAM then base 1:1, then run it at 1:1 and get more overclock out of it.

Considering the minor difference in cost between 667 and 800 RAM its usually worth getting and gives you the option to OC if you want to try later. The costs are minor when looking at a single build, but for the OEMs that make thousands of systems then $10 per system means a lot more and they don't allow OCing anyway and 99% of their users wouldn't be able to tell the difference of running faster RAM.
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August 8, 2007 12:19:34 PM

When ppl say FSB they dont mean like 1066, 1333. Thats your FSB "quad pumped" Your actualy FSB would be 266 or 333. SO running ti 1:1 means running your memory at 266mhz/333mhz, and because it DDR2 its effective frequency is 533mhz/666mhz.

So to use PC2-6400 memory at its optimal frequency of 800mhz, you need to have a 400FSB, or quad pumped, 1600.
August 8, 2007 11:15:49 PM

No one answered this question.

"So even thought 800 isn't running at 1:1 with the fsb, I will still see a performance increase from my current 400, or 533 for that matter?" Even if I don't intend to oc, will it be beneficial?
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