I am new to this forum so hello everyone. And special thanks to ******* who's advice has helped a lot with FSX. I have been experimenting a bit with teh Affinitymask entry and here is my observation (no definitive advice, just what I have seen on my system, Core 2 Quad Q8400 @2.7, 8800GTS 320MB, 8GB DDR2 800, Win7 64 and SSD):On my Quad Core, I use affinitymask 11 which enables Cores 0,1,3. While I know that FS will always use Core 0 even if disabled, it appears that add-ons such as PMDG 737 benefit from being able to use Core 0 and otherwise have to "fight" with the texture engine for time on the other cores. Not enabeling Core 2 also appears to leave room for other FS-activity because Core 2, though disabled by this setting, does show between 13 adn 40% usage (no other applications open). Flying the PMDG, in cockpit view, Core 0 has a 100% load, in outside view, Core 0 load goes down to between 60% and 80%.Since settign affinity mask to 11, sim runs smooth as silk, no micro or other studders.Regards,Michael