Even when you use 2 cards in SLI or crossfire mode, you don't see the full power of the combined cards, but you might get 30-50% more performance in an application that supports multi-GPU's.
My feeling is that you are always better off with a single, more powerful card, unless money is no object, then you may as well get two of the best.
I wasn't aware that FSX did not support SLI ?
You'll find that dual cpu's are not fully supported under XP and that more than 2 ram slots will usually hinder performance. 8gb of ram is like having a swimming pool full of water to give a fish a drink
Programs use a set amount of ram and that's it, any more is wasted.
If you tie a cat onto a rope and swing the rope around and the cat hits the wall, you haven't got enough room to swing a cat. So you go into a big shed, swing the cat, and the cat doesn't hit the wall, so you can comfortably swing the cat. It doesn't help anything at all if you go out into the rain to swing the cat, (unless you really, REALLY hate cats). RAM is working space for the cpu, it needs enough room to perform it's functions without being restricted, and that's all.
As soon as ram becomes restricted, the software/cpu writes the data to the hard disk where it can later be retrieved as the cpu needs it again.
Because this "virtual ram" area on your hard disk is mechanical, and not magically suspended by electricity as in the system ram itself, the PC will slow down a LOT when it reads or writes to the hard disk virtual memory, (or page file).
Much software writes to the page file regardless of the amount of ram, including some windows functions. It is possible to use huge amounts of ram and run EVERYTHING in ram for a super fast system, but the system will usually crash when an error flag interupts the program because a read or write to the pagefile could not be performed.
If software did not page data when required, the program would crash as soon as the ram was used up.
RAM is expensive to make, the first 1 megabyte sticks were reported to cost about a million bucks here in Australia.... I'm not sure that is a fact, but cost of ram production has caused nearly all large software applications to use the pagefile because people could never afford to buy enough ram and the technology was limited in any case.
Thoeretically, we could all now use ram drives for computing, but the cheaper production of ram led to software coding that uses a lot more ram, you could say that coding has become very inefficient and sloppy because the programmers can waste huge chunks of ram to do very little work, but also, modern coding uses lots of little programs that are held in memory, or subroutines that are held in ram so they can be called up multiple times. The subroutines held in memory use a lot of ram. Program languages are a lot more hefty as well, using more ram in the final compiled programs. Programmers in the old days used very efficient coding languages that were closely tied to the hardware itself, and that was a very difficult thing to do apparently and it had to be done extremely accurately. There are still a few of these guys around, and you'll sometimes see a tiny application (a few kbs) that does a big job.
I'm an enthusiastic novice, not a programmer, so if I haven't explained this well, or made an error, please correct it if you know better.
by rootbeer » Sun Mar 04, 2007 11:05 pm 
Mainboard: Asus P5K-Premium, CPU=Intel E6850 @ x8x450fsb 3.6ghz, RAM: 4gb PC8500 Team Dark, Video: NV8800GT, HDD: 2x1Tb Samsung F3 RAID-0 + 1Tb F3, PSU: Antec 550 Basiq, OS: Win7x64, Display: 24&
