# DDR Memory help

by biferi
Tags: memory
 P: 176 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?
 P: 2,155 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
 P: 176 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?
P: 2,155

## DDR Memory help

 Quote by biferi 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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