# Help me understand CPU/RAM/FSB...

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I have posted similar questions in different places and have gotten equally confusing results. Some say that you have to match the FSB with your RAM's MHZ rating and some say you don't. I have no idea who to believe anymore, hopefully someone can bring some closure to this issue for me. Here is what I posted on AnandTech... "I am looking to build an E8400 based desktop (if I can find one for sale anywhere!) but am having trouble understanding a lot of the randomly named motherboards and RAM. For instance, when a motherboard reads DDR2 1200 standard, does that mean it requires DDR2 1200? Also, the E8400 states a 1333mhz FSB but after sifting through some threads on this site it seems that most people go with DDR2 800, even on motherboards that read DDR2 1066/1200 standard. So is it okay to go with DDR2 800?" So with a 1333 FSB cpu like the E8400 do I need 1333mhz rated RAM? Thanks!

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Quote:
 Original post by KriscSo with a 1333 FSB cpu like the E8400 do I need 1333mhz rated RAM?

Nope. But it would be a good idea.

Quote:
 Original post by KriscFor instance, when a motherboard reads DDR2 1200 standard, does that mean it requires DDR2 1200?

No, it means that it supports DDR2 speeds up to and including 1200.

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Ok, but it seems that DDR2 doesn't go to 1333, unless I am misunderstanding the naming scheme. So does that mean to get 1333mhz I need to goto DDR3?

Edit... Like this motherboard here which says it supports 1600mhz/1333mhz but also states it wants DDR2 1200...

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Moved to Hardware.

The RAM and motherboard will negotiate the speed that they communicate at, and they will select the lowest available one. So if you have 800 MHz RAM in a mobo with a 667 MHz FSB, the speed will be 667 MHz. Similarly if you have an 800 MHz mobo and 1333 MHz RAM, the speed will be 800 MHz.

You can never swap between classes of DDR. DDR, DDR2, and DDR3 are all different things.

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Related question: I've noticed that OEM computers always use 667MHz DDR2, so I was thinking that I should build my computer myself for the sake of taking full advantage of the CPU (where even a midclass one will go up to 800MHz to 1000MHz)

That brings up the question of, how much performance gain will i see when moving up from 667 to 800, or even 1033?

price of ram for anything above 1033 is ridiculously high, and motherboards too, so I was wondering what the best bang for the buck bus speed is right now. (this is my second quesiton, which bus speed is most worth the money?)

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 Original post by TyroRelated question: I've noticed that OEM computers always use 667MHz DDR2, so I was thinking that I should build my computer myself for the sake of taking full advantage of the CPU (where even a midclass one will go up to 800MHz to 1000MHz)That brings up the question of, how much performance gain will i see when moving up from 667 to 800, or even 1033? price of ram for anything above 1033 is ridiculously high, and motherboards too, so I was wondering what the best bang for the buck bus speed is right now. (this is my second quesiton, which bus speed is most worth the money?)

Do it. Choose ram whose max speed is the same as the FSB speed. Also, my personal favourite optimisation, useful for many tasks, is to have a smaller, higher speed HDD for the OS, and a larger, but slower one for other stuff. Things I want to run fast, like compiling, I do on the faster HDD.

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Original post by speciesUnknown
Quote:
 Original post by TyroRelated question: I've noticed that OEM computers always use 667MHz DDR2, so I was thinking that I should build my computer myself for the sake of taking full advantage of the CPU (where even a midclass one will go up to 800MHz to 1000MHz)That brings up the question of, how much performance gain will i see when moving up from 667 to 800, or even 1033? price of ram for anything above 1033 is ridiculously high, and motherboards too, so I was wondering what the best bang for the buck bus speed is right now. (this is my second quesiton, which bus speed is most worth the money?)

Do it. Choose ram whose max speed is the same as the FSB speed. Also, my personal favourite optimisation, useful for many tasks, is to have a smaller, higher speed HDD for the OS, and a larger, but slower one for other stuff. Things I want to run fast, like compiling, I do on the faster HDD.

Many motherboards include a RAID controller these days, 3 320GB 7200RPM drives are about the price of 1 150GB 10000RPM drive. Higher speed drives are louder and more prone to failure. Just something to consider on that end.

I have an E6750 1333, and the two GB of DDR2-800 in dual channel mode has been offering great performance for me. (And I never got around to fiddling with stuff on this computer. I really should go and optimize it at some point)

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I don't really see the necessity of 10k drives. They are loud and expensive. I rather buy a reliable low cost solution and wait for SSD drives to come down in price.

Thanks for the help fellas. I went with a Q6600 and 4gb of DDR2 800. I simply couldn't find the E8400 anywhere.

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So, I'm going to mostly ignore the hardware discussion for now, since it seems to have been covered well.

What I *am* going to do, however, is maybe save you some money, and get you a better-quality CPU at the same time! Here's how this win-win situation works -- Instead of buying the e8400, go find yourself a Xeon e3110, these are the exact same chip just re-branded for the server market, in fact, the Xeon-badged parts are actually binned higher (in other words, they typically run cooler and display better voltage characteristics) they have the same speed, FSB and socket connection as the e8400, and should work in every motheroard that supports the e8400. Currently, they're about 35 dollars cheaper using the best prices that Pricewatch.com has aggregated. If you're willing to get in line, Buy.com has them here for just $213, which is about$70 bucks cheaper than the Pricewatch's best e8400 price... Taking a look, Buy.com also stocks the e8400 at the same price, so you can do that if the Xeon makes you nervous (though as I said, the Xeons are binned higher.) Oh, and nevermind that some Xeon adds might say Socket 771, all 'e' class Xeons are Socket 775, same as their desktop counterparts.

Also, something that seems to have been ignored here is that the base FSB frequency currently used by Intel is 333Mhz -- They use a quad-pumped protocol, so that's how they arrive at their 1333Mhz FSB statements. DDR uses a double-pumped protocol, So you divide by 2 to get the base frequency. That's why most Intel's are paired with DDR2-667 memory -- that matches the base FSB frequencies at 333Mhz, giving a 1:1 ratio.

I have personally just purchased the Xeon 3110 for my new rig. What I'm going to do is overclock to a 400Mhz FSB, which will have the CPU running at 3.6Ghz. I'm combining this with 4 gigs of low-latency DDR2-800 RAM which has the nice effect of being able to run a 1:1 ratio between the upped FSB and RAM clock speed. Combined with an aftermarket air-cooler, the CPU will actually run cooler than stock speeds with the stock cooler. Any decent motherboard will easily hit 400FSB if the BIOS allows (many can hit 500+) since they're already prepped for Intel's next CPU refresh which will use a 400Mhz FSB by default. After tossing in a Geforce 9600 GPU and case, I'm about to have a pretty monstrous rig for around \$800.

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