DDR3 RAM "real" speeds

Hey all, this is my first post and was needing some information. I have done a little research on the net for the answer to this question, but not really a whole lot that is helpful. My journey first started by reading how to OverClock and came to a page that actually quoted a post by a user on the OC Forums. The quoted text only referenced DDR Ram (it is unknown to me if that was due to beginners simplicity or due to it being out-dated...more than likely its the latter since the post the quoted the OC tutorial was made in March 2005). Anyway it was making reference to PC-xxxx and it's DDRxxx equivalent. It then explained that if something is DDR400 for example it's "real" speed is 200 since it's double data rate. Now, since DDR3 is the "new" RAM would you figure out it's "real" speed the same way, or is there an extra step or different calculation that is needed because it's DDR3. i understand it's still Double Data Rate, but does the 3 in it require a different approach to figuring?

For example the Memory that I have is 1333MHz PC3-10666 (although it also has PC12800 as the memory speed elsewhere on the page??). What is it's "real" speed so that I can know how fast I can set my FSB speed without problems (That is, only taking into account FSB speed and RAM speed)

• Memory Type: DDR3
• Memory Speed: PC12800
• Memory Speed MHz: 1600MHz
• Total Memory Size: 4GB
• Memory Modules: 1
• Memory Channels: Dual
• Memory Socket: DIMM
• Pins: 240
• ECC: No
• Memory Buffer: Unbuffered

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It's the same. DDR3-1600 is actually 800MHz, and 1600MHz effectively. The number just signifies a "version" number, for lack of a better term. As the version number increases, the speed increases and required voltage decreases as RAM technology gets better.

MattNo5ss said:

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It's the same. DDR3-1600 is actually 800MHz, and 1600MHz effectively. The number just signifies a "version" number, for lack of a better term. As the version number increases, the speed increases and required voltage decreases as RAM technology gets better.

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Thank you for the welcome and the information

So in theory if the processor could handle it, the FSB could be set to 800Mhz? (again, taking only the CPU and RAM into consideration as if they were the only components in the computer)

Yeah, if the FSB could be set to 800MHz the FSB:RAM ratio would be 1:1. In other words, DDR3-1600 can handle a FSB up to 800MHz before OCing the RAM. However, there aren't any 800MHz FSB chips, so it's just theory like you said.

The "DDR-X" number is the MHz rating, which is DDR (double the bus speed). The "PC-X" number is the effective speed in MB/s (MHz * 8), so DDR3-1333/PC3-10666 (or 10667 or 10600 or 10700, various manufacturers all advertise different numbers) runs on a 667MHz bus, and can do around 10.67GB/s.