I didn't want to turn this into a Windows bashing thread... The example I'm using is the minimum system specs printed on computer game boxes. They have one minimum spec for Windows XP and another minimum spec for Windows 7/Vista. It is nearly double the CPU and double the RAM for 7/Vista.
Sure, but then again, under 7/Vista you get DirectX11 support. There are two interlinked issues here. Firstly, the minimum requirements for the game always include the minimum requirements of the OS. So, let's put that in context.
XP is over a decade older than 7. The change in machine specs between the two are actually not so bad. Twice the CPU power and twice the RAM? That's nothing. in that 10 years, the average (per core) CPU power has gone up about 8 times and installed RAM has certainly increased my more than a factor of 2.
Second point to consider is that many games these days use 3rd party engines that are designed to scale across different hardware.
If you are running XP with DX9, the chances are you are also running it on older hardware. Game engines will restrict all kinds of performance sensitive features when they run on such a configuration. A side effect of which is that they now require also lot less horsepower to run. If you want to sell as many copies as possible, you are not going to restrict your sales by failing to inform owners of older hardware that it will in fact run in half the RAM and with half the CPU requirements of somebody sporting newer kit where they can crank up the settings past what your machine is capable of (but requires that extra power to do so). That would be very foolish.
Shove the same software into a system with windows 7 / DX11 and the engine is free to use much newer features, some of which require many times more processing power, be it on the CPU or the GPU, than an XP/DX9 class machine had available.
