CPU-Z and RAM MHz beginner question

[Dancer]

Hi, I just ran cpu-z for the first time and was puzzled by the my RAM max bandwith.

I have GeIL PC6400C4 800MHz Ultra Low Latency DDR2, so I was a bit surprised to see max bandwith as "Pc2-6400 (400 MHz) and in the Timings table the frequencies 200 MHz, 266 MHz and 400 MHz. Shouldn't it be running at 800 MHz?

The DRAM Frequencey is around 358.7 MHz with FSB : DRAM 2:3. I'm trying to read about what this all means, but I'm finding it a bit confusing. Anyone who can help me a bit.

 

[AndyOcUK]

Its DDR (Meaning Double Data Rate so 2 X 400 = 800MHZ or in your case at 358.7......

358.7 X 2 = 717.4MHz

DDR Ram is able to transmit and recieve data on both the rising AND falling sides of the clock cycle which theoretically doubles its speed.

The 6400 relates to the RAMs ability to theoretically shift 6400MBs (6.4GB p/s) of data. (Bandwidth)

Some interesting reading here mate:

http://www.howstuffworks.com/ram.htm

 

[Cob]

Go by the Memory tab, and double the speed as you're using Double Data Rate memory.

So your memory is currently running at 717.4mhz (358.7 x 2).

 

[ns400r]

The 'tables' are read from a small chip on the memory and are there to ensure compatibility with motherboards so the ram will work. To use the proper rated settings you will have to manually configure your memory setting in the BIOS.


E.G. CPU set at default 7 x 333 - 2331MHZ.
Take the base MHZ figure that your CPU is set to in the BIOS and multiply it by the memory mutliplier setting. So if your CPU is running at say 7 x 333MHZ and your memory multiplier is set to 2.0 times then you'll end up with a memory speed of 666MHZ. This is then doubled as you are using Double Data Rate memory to give a memory speed of 1333MHZ.

These setiings can be adjusted in the BIOS depending on the type of BIOS/motherboard used.

 

[Dancer]

Exactly the sort of answers I was looking for, many thanks.