I am the professional software developer with experience either in C/C++, Java and (unfortunatelly mostly in) .Net. No, the clock speed is absolutely not on par with the performance, not anymore :-( (used to be 10 years ago). I have AMD Vishera with 4.5 GHz, which is roughly on par with 3.5 GHz Intel Ivy Bridge. Very roughly. I3s have no less single-core performance than i5 or i7 - they are the same chips*. Memory sizes, which can affect the overall performance a lot, vaires, so most expensive i3 can be more single-core performant than cheaper i5 or i7 (with same amounts of L1 L2 and L3 cahe). What varies is the number of cores, i3 being dual core, i5 quad and i7 quad but to the operating system the i7 will announce they are 8 core. Having i7 has no advantage in X-Plane over i5, so save your money ;-) . The "virtual" cores (called hyper-threading in the Intel's slang) is great for office/server use, but pointless for number-crunching. And heavy number-crunching is what the X-Plane does. It's a simulation and every simulation is about math. Very advanced math. Intel processors could be a bit better for X-Plane - they have better single-core performance and have the L3 cache. L1 and L2 caches are tied to a processor core, they are small but very fast memories. L3 is shared between cores, a lot slower than L1 and L2, but way faster than RAM. If a processor needs to acces a value in L1, it's almost immediate. L2 is a bit slower. L3 is slow. But to get it from RAM ... the processor can walk to India, select a tea plantage, collect the best leaves, dry them, return back to Europe and make a very good tea before the RAM will provide the value. So having money, opt for i5 with newest architecture (not Sandy Bridge, but Ivy Bridge) and biggest caches. If you can't afford i5 (or don't want to spend the money), I'd go for AMD Vishera, the faster, the better. Get the black edition (unlocked multiplier) + aftermarket cooling (if you are from Czech Republic or Slovakia, you can shop for this one http://www.alfacomp.cz/php/product.php?eid=1051400000000002MYM or get it from your local reseller if you are lucky enough not living in our little afghanistan - in EU it's roughly 18-20 GBP) and overclock it as hard as you can. I'd definetely choose 4 core Vishera over 2 core Ivy - Windows and other programs just don't understand you are playing a game and want best performance from you computer. Even X-Plane can use more cores than only one, that's different from MS Flight Sim. But ... asking questions on the internet is something like asking questions on the streets of London. You never know who will answer. I'm not developing X-Plane and I have it solely for entertainment, because getting pilot license is not cheaper here than in western europe, but GBP 7k yearly is average salary here. May be it would be not bad asking the X-Plane developers directly - and if you do and they tell you something different than I did, please let me know - you will help stop spreading bullshit over internet :-D . * There's a joke that they make i3 form the exactly same silicon as i5 and i7. But the natural silicon is not perfect, so if some of the cores are FUBAR level one (FUBAR lvl1 = f***ed up beyond any repair, FUBAR lvl2 = f***ed up beyond any recognition), they just disable two most FUBAR cores and sell it as i3.