Basically the title says it all.This is my situation. I got a FX55 and a Gigabyte GA-K8NSC-939. The problem is that I have 2x512Mb and 1x1Gb Ram sticks. All PC3200, 400Mhz. The Mainboard only allows me to use the sockets (4) this way:1 Stick only: in the #1 socket.2 Sticks: in #1 + #2 which enables the dual, or #1 + #3 which keeps the memory as single chanel.3 sticks: No possible configuration (unbootable system)4 sticks: duh!You would say that the best answer is #1 + #2, with the 1G + 1 512. The problem is that for some reason the 1G overrides the 512 and the system only sees the 1G (either in socket 1 or 2) and ignores the 512 one (in either socket too). So my guess is that the only way to enable dual is to install 2 identical 512s or 2 1Gs.So here comes the question again: If the only way to enable dual channel is by installing 1G (2x512) and otherwise, if I install 1.5 I have to keep it as single channel, what gives the best performance?Sorry for the puzzle ;).Thanks,LeoPS I know I must get at least another 2x512 or a 1G stick/s, but have spent a lot already, so I will hold some days until I am sure this thing is 100% worth.

So my guess is that the only way to enable dual is to install 2 identical 512s or 2 1Gs.This is correct. Most motherboard manufacturers recommend memory of the same size, brand, and speed in order to achieve a dual channel config.So here comes the question again: If the only way to enable dual channel is by installing 1G (2x512) and otherwise, if I install 1.5 I have to keep it as single channel, what gives the best performance?Sorry, but there's no simple answer here. It depends upon things like OS config, software application, hardware, etc. For some testing of dual vs. single channel check this out. I've not found any data comparing single and dual in FS9, but this sim is getting a bit aged and might not care much about the single vs. dual channel issue. Unless someone can offer test results in this sim you'll probably have to do the benchmarking yourself. Depending how you have your OS and FS9 configured, and how many and what types of add-ons you sim with, you may prefer 1Gb of dual channel or the larger 1.5Gb in single channel.With regard to your "PS", of course adding a second 1Gb stick is preferred. Just be certain that it is exactly the same stick you already have. This will take careful checking (to the extent of contacting the memory manufacturer to insure that what you are about to buy is precisely the same as what you already have). Try not to wait too long... most memory manufacturers tend to change their line-ups almost as fast as a gambler can shuffle a deck of cards. :-) Good luck,Greg

Like Greg said, you have to be very careful when trying to configure memory. Almost ALL motherboard manufacturers advise against using memory from different manufacturers that isn't "matched." You say that they are all PC3200 DDR 400 but do they all run the same timings, are they 2 3 2 6 or 3 3 3 8, is it 1T or 2T. There are just a lof of variables here. Are you running a socket 754 processor instead of a 939 if it is AMD. The 754 don't support dual channel. Like I said, a lot of variables but if you give us ALL of the specs we MIGHT be able to help.We just need to know more before we can really answer that correctly...-PaulLiquid CooledAMD 4000 San Diego2 Gigs Kingston Corsair XMS CL2Dual 7800 GTX 24 inch widescreen dual 19 inch LCDRaid-0