I currently have an i7 2600k turbo'd at 3.5 GHz. I use my PC for work as well and I don't want to overclock a PC that I do my work on. I already have a GTX 580 video card, so my video card is way more than enough for FSX at 1080p. If I upgraded to an i7 3930k would I lose performance in FSX since the 3930k is 200 MHz slower even if it has more L3 cache and more RAM bandwidth than the 2600k?

I would keep the i7 2600K. It handles FSX very extremely well w/o overclocking and I cannot see any justification whatsoever to 'upgrade' to a CPU costing hundreds more.Best regards,Jim

Stick with the 2600K. Useless really to get a 3930. They dont show a big enough improvement for the price.