is my RAM messed up

Jeston

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Mar 29, 2007
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I got

2048MB [1024MB X2] DDR2-800 PC6400 Corsair XMS2 Xtreme w/Heat Spreader

And i dont know why the CPU-Z is saying that each one only has 400Mhz when the ram is 800mhz - IS MY RAM BROKE? heres 3 pictures

This is RAM #1
78520881aq9.png


RAM #2
39851230wd5.png


And the overview of my RAM
67426673dx2.png



also my PC system info reads it as 2.00GB see
80615405bm7.png


Plz tell me why my RAM is 400Mhz and not 800Mhz

Thanks
 

Tegrat

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Feb 27, 2007
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DDR2 800 = (400MHz FSB (100Mhz x 4 Intel quad pumped)) x 2 (DDR - Double Data rate)

Your RAM is where it should be!
 

miribus

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Nov 28, 2006
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Agree with above, the problem is it depends on the bios or the program that recognizes it. For whatever random reason, one designer decides to show the clock frequency, the other decides to show the instructions per cycle.

How it basically works is this.
Your memory runs at 400mhz, this frequency looks like a waveform
Because it is "double" data rate it can move memory on the bottom of the arc as well as the top, performing twice the amount of data per clock cycle, effectively making it 800mhz. So the clock frequency itself is only 400mhz but it moves so efficiently that it moves 800 instructions, not 400.

Depending on the software engineer he might choose one or the other to display as your memory speed. Both are technically correct. But, since 400mhz is your frequency and is tied to the FSB calculation, the 400mhz is actually more important since that is really the number the rest of the system cares about. So most will show the frequency.
 

Mondoman

Splendid
Just to clarify, the memory bus clock is independent of the FSB clock. Your 3rd CPUZ picture shows the current memory bus clock of 400MHz; Double Data Rate (DDR) RAM transfer two chunks of data per clock cycle, resulting in a *data rate* of 800MHz.

Your first 2 CPUZ pictures show the SPD info stored in the memory modules, *not* the conditions under which the RAM is actually being run.
 

miribus

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Just to clarify, the memory bus clock is independent of the FSB clock.

Yes, the FSB and the Memory are needed to be the same speed, however the frequency that your FSB is, affects your ram frequency. The ram is run at a frequency "related" to the FSB frequency. If you change your fsb, you change your memory speed in a relative manner at the same time.
 

Mondoman

Splendid
...
Yes, the FSB and the Memory are needed to be the same speed, however the frequency that your FSB is, affects your ram frequency. The ram is run at a frequency "related" to the FSB frequency. If you change your fsb, you change your memory speed in a relative manner at the same time.
To clarify further, the FSB and memory bus do *not* need to be the same speed. As for setting the memory bus frequency, some MBs do make you specify the FSB:memory ratio, in which case changing the FSB thus changes the memory bus frequency. Other MBs allow you to set the memory bus speed directly; on those, changing the FSB speed has essentially no effect on the memory bus speed.
 

miribus

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Yes, the FSB and the Memory are needed to be the same speed

Wow, I'm an ass who unwittingly contradicted them self.
What I meant to say was that the memory and fsb are independant, in that they are not the same speed, but their frequencies are tied together in that effecting the FSB will effect the memory speed.

But instead, I wrote something that even I don't understand.

Other MBs allow you to set the memory bus speed directly; on those, changing the FSB speed has essentially no effect on the memory bus speed.
I believe, what you are setting independantly is a divider that mitigates the effect the front side bus has on the memory speed. If you over clock your fsb 10% for example, you overclock your memory 10% of whatever divider you had it at. Give or take a percentage. Granted there may be extra dividers to effect this more, but it's still tied in. Though it really only matters for under/overclocking which the OP hadn't mentioned and I don't even know why I brought it all up. TMI habit I guess.
 

Mondoman

Splendid
Other MBs allow you to set the memory bus speed directly; on those, changing the FSB speed has essentially no effect on the memory bus speed.
I believe, what you are setting independantly is a divider that mitigates the effect the front side bus has on the memory speed. If you over clock your fsb 10% for example, you overclock your memory 10% of whatever divider you had it at. ...

On this latter type of MB (of which my NI8 SLI is one), you do actually set your target (fixed) memory bus speed directly. If the FSB is later varied, the BIOS automatically calculates and sets new divider settings that maintain the memory bus speed as close to the target speed as possible (typically, within about 10-15MHz, which is why I used the word "essentially" in my original post).

To me, this seems like the "natural" way to have the BIOS work, but I'm sure there are those that prefer the explicit divider method.