Memory
illucine Jul 28, 2011 11:02 AMAs a first-time builder, I have a lot of questions about memory. I'll probably be running a 990x on a X58 motherboard but haven't narrowed it to a specific board yet. Also, I probably won't be overclocking at first but would like to eventually as I become more knowledgeable and gain more confidence (in both the computer and myself).
So first off, is 1333 MHz the fastest memory can run on this type of system without overclocking? I assume that faster memory will still work, it just won't run at it's full rated speed until it's overclocked. What about XMP profiles – I've read that by selecting an XMP profile in the BIOS, that memory can safely run at higher settings without getting into all the detailed parameters of overclocking. Is that more or less correct?
It seems like as the speed rating goes up the latency rating goes down (generally). Which is more important?
What about mixing modules of the same type? I know it's not good to mix different speeds/brands/etc. But what about something like buying 6x 4GB modules versus a matched 24GB kit? I've heard that's risky and can sometimes work ok but other times not. I found a 4GB module from Corsair (CMX4GX3M1A1600C7) that seems to offer both decent speed (1600 MHz) and low latency (7-8-7-20) but am concerned about running 6 of these unmatched. BTW, I don't understand what all the individual numbers mean but believe that the lower the better (for latencies).
Most of the memory modules I've looked at are rated at either 1.5 or 1.65 volts. What's the difference – is it simply a matter of adjusting the voltage on the board or in the BIOS?
I heard something a while back about performance issues with more than a certain amount of memory. For example, a system with 24GB actually running slower than a system with 12GB. I find that hard to believe. Has anyone heard of that?
Finally, I'm undecided about the need for ECC memory. Contrary to what many people say, it's not just for servers. Most workstations, such as the HP Z800, Dell Precision, Mac Pro, etc. use ECC. Some studies have indicated memory errors are much more likely than is commonly assumed. Building the Perfect PC recommends using ECC memory if you install more than 8GB (I'm going for 24GB). On the other hand, the majority of computers do not use ECC memory. I realize it's a little more expensive, less options available, and possibly incurs a slight performance hit. And you need a Xeon to support it. I go back and forth on whether ECC is important. Does anyone running large memories (>16GB) have problems they could attribute to not using ECC?



