Question on Ram / Ram timing

[gizbug]

My CPUZ reads as follows (in bios I have the ram set at 667 speed)

Frequency: 333.3MHz
FSBram 9:10
CAS 4
Ras to Cas delay 4
Ras 4
Cycle Time 12
Bank Cycle Time 19


NO idea why it says 333.3MHz when I have it set to 667 in the bios.

It is 4 sticks of Crucial DDR2 ram (4 1gig sticks)
Motherboard is ASUS P5N32 SLI Se Deluxe
Vista 64.

Any help would be appreciated.

 

[airhendrix13]

I'm pretty sure everythig is fine here.

Your BIOS is showing you your effective FSB while CPUZ is showing you your actual RAM speed. Basically, there is a 64-bit bus that connects your processor to your northbridge and a memory bus connects the northbridge to the RAM. The memory bus is running your memory at half its rated speed for one reason, your RAM is running in Dual Channel. This means you have 2 sticks of RAM, each stick doing half of the work. So 333.3MHz for each stick, add them together we get 666.6MHz, round up and we get 667MHz.

The simple answer is CPUZ is reading each stick of RAM individually, while your BIOS is pairing up 2 sticks of RAM and giving you the total dual-channel speed.


Everything is fine, nothing to worry about here.

If you need me to explain further I certainly can.

Ryan

 

[Aikouka]

I'm pretty sure the reason you double the effective RAM speed is because it's DDR(2), not because it's dual-channel.

EDIT:

As mentioned in Wikipedia's DDR article:

It achieves greater bandwidth than the preceding single-data-rate SDRAM by transferring data on the rising and falling edges of the clock signal (double pumped). Effectively, it nearly doubles the transfer rate without increasing the frequency of the front side bus.

Thus, a system with a 100 MHz front side bus has an effective clock rate of 200 MHz when DDR SDRAM memory is installed. The same system using SDR (single data rate) SDRAM, will not have its front side bus rate doubled and be limited to a 100 MHz front side bus speed.

 

[airhendrix13]

Yes, that very well could be it. DDR2 does 2 reads and 2 writes in one clock cycle.

But in the end, the point is that gizbug's pc is just fine.

Thanks for the correction Aikouka.

 

[MarcVenice]

Heh DDR stands for double data rate. Aikouka explained it pretty well. DDR2 and DDR2 are both double pumped. The 2 in ddr2 simply stands for the next generation, like ddr3 is the succesor of ddr 2.

 

[xitshsif]

http://en.wikipedia.org/wiki/DDR2

The key difference between DDR and DDR2 is that in DDR2 the bus is clocked at twice the speed of the memory cells, so four words of data can be transferred per memory cell cycle. Thus, without speeding up the memory cells themselves, DDR2 can effectively operate at twice the bus speed of DDR.

 

[MarcVenice]

Learn something everyday. I wonder how performance actually differs between let's say a s939 rig with pc3200 ddr ram, versus a am2 rig with ddr2 pc4200 ram, with the same cpu.

 

[xitshsif]

DDR2 generally has significantly higher latencies than DDR. DDR running at the same bus speed as DDR2 will be faster. However DDR2 is able to run at much faster bus speeds and at lower voltages.

DDR3 will be the same again: higher latency than DDR2, but much higher bus speeds and lower voltages.