DDR3 1333 differences??

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DDR3 1333 differences??

Postposted on Fri May 06, 2011 12:08 am

I've noticed while looking at DDR3 1333 ram, I see pc3 10600, 10660, and 10666. What are the differences? Will any of the 3 work with an AMD motherboard that specifies DDR3 1333 (assuming it is unbuffered/unregistered)? Why is 1333 the only memory that has these 3 different speeds?
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Re: DDR3 1333 differences??

Postposted on Fri May 06, 2011 5:41 am

Looks to me like different vendors are just rounding off to a different number of significant digits.

(Well technically I guess they are not rounding, but truncating... :lol:)
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Re: DDR3 1333 differences??

Postposted on Fri May 06, 2011 6:27 am

just brew it! wrote:Looks to me like different vendors are just rounding off to a different number of significant digits.

(Well technically I guess they are not rounding, but truncating... :lol:)



+1 on this answer :)

1333 should be the standard rating. For that module They just get lazy with the numbers moving forward.


If you're curious, I'm not sure where all the numbers come from (or what they're called) but I know there's a lot of "x8" involved" and it's supposed to work like this:

1333 memory has a memory clock of 166.66 Mhz internally. That gets multiplied x4 I guess for the "memory bus rate" and x2 again because its double data rate. So:


1666.66 x8 = 1333.28. that's where your rating comes from.

Now here's where it get's tricky. It's transfer rate is 8x that number. I'm not sure why, I'm guessing because DDR3 is 64 bits wide in the transfer path (?). 64 bits = 8 bytes. So every second there's 1333.28 8-byte transfers? Anyway:

1333.28 x8 = 10666.24, or your PC10666


From there, I guess it depends on how lazy you are. If you do 166.6 (instead of 166.66666666) x8 x8, you get 10662.4, which is easy to truncate down to 10660.

Or if you do 166 x 8 x8, you get 10624, which looks totally odd. then you look the original DDR3 800, which has a transfer rate of 100 x 8 x 8, and see that 6400 ends in nice double 0s, and decide it looks a lot neater if I truncate down to double 0s and list my module as PC10600.

...until some other vendor comes along and says, they're selling PC10600, but since technically, 10666 is correct, I can list that for my memory and make it look faster (and more satanic). Let's give that a go! :)


Hope that helps?
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