:) Except, the actual systems on the actual aircraft doing the actual calculations rely on 286, 386, 486 and sometimes lesser CPUs. (that was fun to write).
The Space Shuttle uses 5 APA-101S computers (5 for redundancy) at about 1.2 MIPs with a couple of megs of Ferrite Core memory (defense against radiation). The entire control for the shuttle is <1 MB of program. The updated, state of the art (heh) glass cockpit shuttle got an upgrade to a... wait for it… Intel 386.
The DFCS and FCS of an F-16 CPU runs at about .5 to 1 MIP comparable to a Motorola 68000 processor.
Today’s processors like the ones sitting on your desk push 55,000 to 175,000 MIPs never mind the gigaflops for the required math.
Math just isn’t the issue in modeling these systems on modern CPUs. Which means we’re left with world physics such as gravity, wind, pressure, motion... flight model.. but that is just more of the same math calculations-- something that processors since the incarnation of the math coprocessor (now integrated into any modern cpu) have dealt with like a sledgehammer on an anthill. Then there’s the graphics.
The developer of X-Plane (as well as one of the leads of Aces) put it best and to paraphrase, it mostly comes down to the graphics engine. Graphics, graphics, and graphics. Until sim engines are developed to make better use of today's multicore systems, we’ll have to deal with throwing clock cycles and heat at it (read, gigahertz)—that and moving towards modern graphics APIs such as DirectX11 and OpenGL 4.3. Quite frankly it’ll be much easier to implement support of newer graphics APIs rather than to make revolutionary strides in polycore. Incidentally, this is what Lockheed Martin and Laminar Research are doing with their sims while they make iterative improvements on multicore support. Multicore is doable (Playstation 3), it’s just that it’s damn hard.
BF3 runs as well as it does because DICE has a very good dev team that spent a lot of time, intellectual capital, and fiscal expense in developing their Frostbite engine. They know their way around DirectX and the popular gfx architectures that run them. You can read some of their dev blogs that mention the obstacles they had to overcome as they developed what they have now.
I’ll close with this question. How fast do you think Falcon, FSX, and DCS products would run if it didn't have to render the outside world-- just its panels, flight models, and systems?