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What is important when looking fir RAM?

post #1 of 2
Thread Starter 
Sorry for noob question.

I want to get some DDR2 RAM for a AM2 system next year.
I'm somewhat confused about timings, CL values, bandwidhs and speeds.
Could somebody clear me up here?

There is this CL value. I understand that lower is better.
Most today have 4 or 5. How can it be that my low cost MSI memory from
2004 has much better CL2?

Then theres chip speeds like DDR2-800 and module bandwidh like PC6400.
What do these two mean?

What do I have to look out for when buying?
What makes RAM fast, what makes it run stable?

Thanks
    
CPUMotherboardGraphicsRAM
AMD Athlon II X3 435 Asus M4A77TD Pro Radeon 4890, 1GB 2x2GB DDR3 1333 
OS
Win 7 
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CPUMotherboardGraphicsRAM
AMD Athlon II X3 435 Asus M4A77TD Pro Radeon 4890, 1GB 2x2GB DDR3 1333 
OS
Win 7 
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post #2 of 2
For AMD rigs, tight timings are generally a good thing (as opposed to Intel rigs, which like high bandwidths and don't care too much about timings)

Generally, smaller RAM modules have tighter timings than larger ones. Also, DDR RAM has tighter timings than DDR2. That's why your small DDR RAM sticks have much better timings than the (probably 1GB?) DDR2 sticks you have been looking at.

The number behing the DDR2 indicates the max. frequency the RAM runs at at stock speeds. Thus, DDR2 800 runs at a frequency of 800MHz. Since it's DDR2, the external frequency is 400MHz. Since AM2 CPUs run on an HTT or 200MHz, the DDR2 RAM that runs 1:1 with the CPU is DDR2 400. Now, I assume you want to overclock, so it's best to pick RAM at a higher frequency, like DDR2 667 (which allows your HTT to go up to 333MHz before hitting the stock speed of the RAM).

The number after the PC indicates the max. assumed bandwidth the RAM can handle at stock speeds. In practice, it's often a bit lower though, given all kinds of other restrictions (memory controller, etc).

For your AM2 rig, I would look for DDR2 667 RAM with as tight a timing as you can find.
    
CPUMotherboardGraphicsRAM
E8400 @ 3.8 GHz DFI LANPARTY DK X38-T2R eVGA 8400GS 2GB Mushkin DDR2 800 (single stick) 
Hard DriveOptical DriveOSMonitor
250GB WD SATA None Windows XP Pro 32-bit HP Pavilion f1703 
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N/A Corsair HX520 Coolermaster Cavalier N/A 
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CPUMotherboardGraphicsRAM
E8400 @ 3.8 GHz DFI LANPARTY DK X38-T2R eVGA 8400GS 2GB Mushkin DDR2 800 (single stick) 
Hard DriveOptical DriveOSMonitor
250GB WD SATA None Windows XP Pro 32-bit HP Pavilion f1703 
KeyboardPowerCaseMouse
N/A Corsair HX520 Coolermaster Cavalier N/A 
Mouse Pad
N/A 
  hide details  
Reply
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