One of the biggest challenges for Microsoft when designing any piece of software is maintaining compatibility for the nearly infinite different configurations of hardware. This is especially true for an operating system, which is why Microsoft worked with hardware partners as closely as possible when developing Windows 7.
Intel, being the largest chip maker in the world, played an important part in optimizing Windows 7 so that it'll run well on Intel CPUs.
Joakim Lialias, Intel's Alliance Manager for Microsoft explained on the new Partner blog some of the optimizations: "Working with Intel, Microsoft implemented a new feature called SMT parking, which provided additional support for the Windows 7 scheduler for Intel Hyper-threading Technology, enabling better performance on hyper-threaded, multi-core Intel processors. This will help users get the maximum benefit from multi-tasking."
"Also, Intel and Microsoft jointly analyzed the boot/shutdown/sleep/resume times on Intel platforms during the development of Windows 7 to identify opportunities to optimize Intel drivers and BIOS as well as Windows 7," Lialias continued. "Our mutual goal was to provide the most responsive compute experience possible. Another key part of the performance and responsiveness was our collaboration to optimize Intel Solid State Drive technology for Windows 7."