I am building a PC and have selected my processor (Intel Core i7-930) and motherboard (Asus P6TD Deluxe), and I am now looking at memory. I read somewhere that 4-4-4-12 was a good latency timing and the lower the better, but I am looking at the RAM that is compatible with my motherboard and it is all a lot higher than that. For example, 8-8-8-24, or 7-8-7-20. I would appreciate perhaps a short explanation on what these numbers mean as well as an answer on whether or not these numbers are too high. Also, is there anything else I should know about or look for in relation to memory?
4-4-4-12 is DDR2... DDR3 is 8-8-8-24 or 7-8-7-20. You want the lowest possible timings (DDR3 is Cas6, from what I've seen), if fits into your budget. After that, you want to go with speed. For Example: DDR3 1333 at Cas7 is better than DDR3 1600 at Cas8 / Cas9. DDR3 1600 at Cas7 is better than DDR3 1333 at Cas7. Here is a sticky to give you some more info on memory (it is a little outdated but the general concept is correct)... MEMORY FAQ (please read before posting)
You've likely read an article or review from a few years ago. The CL 4 is on DDR2, which is obsolete. That means 1.) it won't be compatibile with the board and 2.) it would be slower than the DDR3. You should be looking for some DDR3 with CL 7 running at 1333 mhz or 1600 mhz. If you've got a large budget, the fastest sticks on the market are the Mushkin Enahnced Redline 3x2 GB 1600 mhz CAS Latency 6. A more reasonable choice is the G.Skill Pi 3x2 GB 1600 mhz CAS Latency 7.
As far as things you need to know, you need to know a lot. First, since you're building a X58 machine, you need to buy triple channel memory. That means the sticks should come in kits of three (3x1 GB, 3x2 GB).
Second, CL and speed are opposites. The faster the sticks run, the hgiher the timings. Sticks that run at 1600+ mhz will typically have a higher CL.
Third, you need to decide what would be good for your uses. Right now, the sweet spot for RAM is 1333 mhz CL 7. However, if you plan to overclock, 1600 mhz CL 7 is better. As you overclock, you need the sticks to run at a faster speed, but want them to retain a lower CL.
Fourth, you need to pay attention to the voltage requirements. Most boards don't like to have RAM with more than 1.65V. This is especially true with Intel. That means if you get high voltage sticks, they might have some compatibility issues with your board.
Fifth, other than the 1.65V requirement, there is are benefits to getting lower voltage sticks. Mainly that they will overclock better, meaning they will run at faster speeds.
Finally, you need to know that not all boards will automatically set the RAM to the specs that are stated. You should also enter BIOS and manually set the RAM to the manufacturer's listed speed, voltage and timings. If you don't do this, it can cause stability issues such as freezing, BSODs, and many other problems.
I am also pricing out (just for interest and comparison) a PC using the AMD Phenom II X4 965 Black Edition CPU and M4A79T Deluxe motherboard. In looking at RAM for that is there anything that would be different?