Hello fellow forum goers. I have noticed an increase in threads asking which would be better of these two choices on an Athlon 64/Sempron: 4x512mb 2x1024mb ram First, I will clear up some misconceptions of the "limitations" of the A64 memory controller. I will reference this thread often. You can see in that thread that the only benchmarks affected by 1T/2T are gaming benches and memory specific benches (surprise surprise.) You can also see the change in memory speed has a little role in CPU intensive applications like Cinebench rendering and multimedia applications. So that in mind, let's explore our options when forced to run 2T. In this case, to attain 2 gigs, we would almost certainly have 4x512mb of ram. Your memory controller will then be saturated. On anything pre-Revision E (cores before the Venice, San Diego, Manchester, Toledo, Lancaster, Newark, and the "BO" Palermo cores), this would mean a certain memory speed and latency hit, and it would be very noticeable. In this case, 2x1024 would be best, since you could still get 1024 sticks with reasonable timings (2.5-3-2 or so) and use a memory divider to OC the cpu. To push this point, I will show you old robberbaron's list of A64 priorities: CPU Speed! CPU Speed again! Memory timings Memory speed > 200MHz/DDR400 You will find the most performance of all when you are running at your maximum CPU speed, regardless of memory speed and timings as long as they dont fall too far below 3-3-3 and 200MHz. However, for gaming, memory latencies are a little more important. Let's review that counterstrike bench. In the thread that I referenced earlier, you see a drop of about 13-15 FPS across the board when running at a lower memory speed. 1T and 2T have very little difference. Here is some "realworld" gameplay data for CS:Source. 1280x1024, all high, 4xAA 8xAF 2.5GHz with 192MHz memory 1T: 92FPS 2T: 90FPS So, when playing, the more you put a load on your snazzy video card, the less you feel the hit. This is to be expected, so don't fret too much. However, let's see what framerate I'd be getting with a full 10x250MHz 1:1 1T: 109 FPS 2T: 108 FPS So there you have it. Memory speed can get you more performance in games. So it comes down to what you'll be doing with the system, at this point. For gaming, you'll probably want to go with 4x512 of memory that is known to hit good speeds (240MHz or so) and keep decent 2.5-2-2 or 2-2-2 timings. As you can see, you don't have to worry about the 2T performance hit because the memory speed will more than compensate that. Crucial Ballistix fits this bill and is much cheaper than the alternative of GSkill TCCD. Or, you could try your luck with 2 gigs of TwinMOS SP or Mushkin Redline. For basically all else, it would probably be quite a bit cheaper to get 2x1024mb sticks. Some, such as Crucial or Patriot, can have very tight timings at between 200 and 220mhz. So those would be a good choice. Another advantage of 2x1024 is that it leaves some slots empty for future expansion. I hope that you are now a more informed forum in this regard. To those wondering why the A64 memory controller does this, here is the (highly simplified) answer. When it tries to access 4 sticks of double sided ram, it simply cannot run at a quick enough pace. So it turns down to 2T in order to "ease" the "work load." However, this applies to doubled-banked dimms. There are, in fact, single sided 512MB sticks! Yes, there are! http://www.newegg.com/Product/Product.asp?Item=N82E16820146541 That is singled sided. Note the .8T at the end. It means that there are 8 chips total. The memory chips on this dimm are normally used in 1 gig sticks, so think of this as a one gig stick with one side blank. I have no experience with this stick, but I have no reason to believe that on RevE, it can run at full speed with 1T. On pre-RevE, it will definately run at full speed with 2T.