CrucialBL2KIT25664BN1337 PC1333 4GB Memory RAM (DDR3, Crucial Ballistix CL7, 2x 2GB Kit) Retail

I've now got 8GB running (two of these kits) and it runs nicely. I tried several different RAM kits all claiming to be compatible with my mobo which weren't - and some which were unreliable. This is just fine. The packaging is very attractive - the photo on Amazon doesn't do it justice. They've got shiny yellow/orange/gold heat sinks on both sides, and look quite nice and a bit unusual. They're also very easy to fit - this sounds stupid, but with the two heat sinks running parallel to the PCB you've got a nice rigid structure which is easy to handle and to press into the DDR3 slot.Why not 5 stars? Well this had me baffled for ages, and it was only when I came to buy my second kit I twigged. The RAM is sold as PC1333, CL7. This is not earth-shattering in 2012, but I first bought it in Jan 2010 I paid a premium for this spec. However I have never been able to get it to run at CL7. Always CL9. The Amazon listing doesn't give me any hints - and to be fair neither do other retailers (I bought my first kit from eBuyer and they are the same). The trick is that (as you probably know) modern RAM comes with several sets of timing settings stored in it (its own little non-volatile memory called SPD). In this case it comes with four sets: two industry-standard JEDEC ones at 1.50V, 592MHz at CL8 and 666MHz at CL9, and two *special Intel ones* called XMP at 1.65V, 667MHz at CL7 and CL6. So what on earth does all this mean? To get PC1333 CL7 you need 667MHz and 1.65V.If you have an Intel CPU and chipset (which I don't) I understand you can select any one of these four from your settings (BIOS or overclocking app). And it probably works. If you have an AMD CPU and chipset, you only get automatic configuration on the standard JEDEC ones, as the Intel XMP system is proprietary and AMD don't use it. So although the RAM can run at PC1333 CL7, if you want to get in an on AMD you have to tweak it yourself. If you're an experienced overclocker you can probably sort this in a moment. I spent an age trying to get it working, gradually eeking towards the XMP settings, raised voltage etc but could never get the machine stable. So I reverted to CL9, and everything is now fine and dandy.So the message is - this RAM is only as described (CL7) if you have an Intel rig, or are willing to effectively overclock your AMD setup to get it. And if you don't want the CL7, there are much cheaper RAM kits around. So consider this factor before you buy.Phew!