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DDR Memory help

by biferi
Tags: memory
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biferi
#1
Dec4-12, 11:34 AM
P: 193
I know if I have a DDR2 Memory that is 800 MHz and it is 64 Bit the math to findout the Data Transfer is

800,000,000 X 64 = Data Transfer.
But will this give me the Data Transfer in just Bits Per SEC. or MB Per SEC?
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jedishrfu
#2
Dec4-12, 11:56 AM
P: 3,002
This might help:

http://en.wikipedia.org/wiki/DDR_SDRAM

so for DDR-400
200 MHz clock --> 400 MHz data rate
8*400 MHz --> 3200 MB/s

so in your case 800 *8 -> 6400 MB/s
biferi
#3
Dec4-12, 10:17 PM
P: 193
I did have a look at your link and I think this got me more confused.

If I want to know my Transfer Rate for my DDR2 800MHz 64 Bit DiMM in Bytes I do the math like this

800MHz X 64 then take the out come and Divid by 8

Will give me Transfer in Bytes per sec Right?

jedishrfu
#4
Dec4-12, 11:56 PM
P: 3,002
DDR Memory help

Quote Quote by biferi View Post
I did have a look at your link and I think this got me more confused.

If I want to know my Transfer Rate for my DDR2 800MHz 64 Bit DiMM in Bytes I do the math like this

800MHz X 64 then take the out come and Divid by 8

Will give me Transfer in Bytes per sec Right?
Yes, that seems right. I gave you the link because it had several tables where the Hz was listed along with the MB/sec to give you a comparison and perhaps help answer other related questions.

I noticed that a given Hz was doubled because the memory is read on the up cycle and on the down cycle of the clock signal. If the memory is transferred in parallel on a 64 bit or larger bus then your answer 800 * 8 is the MB/sec speed is correct but if say the data was transferred on a smaller 32 bit bus then the rate would be half or 800 * 8 / 2 MB/sec.


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