[Solved] DDR3 1600MHz on GA-EX58-UD4P

Ahh - low latency - that's a different animal! I have posted a comparison so people would know the difference when using 'fast' DDR2:

...people often misunderstand the actual quantitative speed improvements inherent in faster ram... Here's the mistake: 1066 is 33% higher than 800 ([1066-800]/800 = 266/800 = .33), so 1066 RAM must be a third faster than 800, right? Not so! You have to figure in latencies. Most 800 will run at 4-4-4-12, while most 1066 is rated at 5-5-5-15, or, even worse, 5-5-5-18. Here's how to appraise the situation in reality: at 800 MHz, a RAM bus cycle is 1.25 nSec long (1000/800); at 1066 (1000/1066), it is roughly .938 nSec long - so, with an 800 stick at a 4 average latency, a RAM bus transaction takes 1.25 (cycle time) times 4 (latency), or 5nSec, while at 1066 it is .938 (cycle time) times 5 (latency), for a transaction time of (roughly) 4.7nSec - so you see, by going to nominally 33% faster RAM, you actually gain three tenths of a nSec per transaction: .3 (transaction gain) over 5(transaction total) = .06, for a real-world improvement of 6%

With DDR2, and northbridges with on-chip memory controllers, the main advantage in using faster RAM is to 'unbind' the CPU and allow faster FSBs:

Examples: if you set your system clock to 333, you will need a 2.4 memory multiplier (333 x 2.4 = 799.blahblahblah) to run your RAM at 800, and if the CPU multiplier is, say, 8.5, you will get a CPU clock of 2.83GHz; at that same B_CLK you would need a memory multiplier of 3.2 (3.2 x 333 = 1065.6) to take advantage of 1066 RAM. Now, lots of CPUs that are rated at a 1333 nominal FSB will run a lot faster, sometimes with a little more 'oomph' from a voltage increase; for example, I run a Q9550 that is rated at 1333 FSB (333 B_CLK) times an eight point five multiplier, for a 2.83GHz speed. It will comfortably run with the B_CLK well over 450 - and here's where faster RAM comes in. The smallest RAM multiplier available from a MCH (Memory Control Hub - or 'NorthBridge') is 2.0, but, with a 2.0 multiplier, that means at a 450 clock, your RAM will need to run at 900 (again, 450 B_CLK x 2 = 900), which most 800 RAM just won't do! This is referred to as a 'RAM limited bus', meaning the CPU can't run a B_CLK any higher than (roughly) half the RAM's available speed - and thus, the need for faster RAM. Mind you, this only applies if you both can, and intend to, run your FSB above 1600 (once again, a B_CLK of 400+ times 4 gives you a 1600+ FSB)...

I have also posted a little chart to illustrate the process of 'walking up' the FSB, successively raising clocks and lowering multipliers:


What most people just don't get is that a piece of RAM is just, well, a piece of RAM - its timings are actually in microseconds and picoseconds, not latency counts; if it's high latency at 800 (for DDR2), it's still gonna be high latency at 1066, or 1150. What you pay the big bucks for is physically low transaction times - and certainly, with the new i5/i7 architecture, you have a lot more opportunity to take advantage of that, if you're willing to pay for it. But a DIMM that has a 600 picosecond bank access time, is going to need that full 600 picoseconds whether you're running it at 1033, or 2000 - it'll just be more counts of a shorter clock pulse!