1. When hyperthreading is enabled on Sandy Bridge, are the entries in the ITLB, DTLB and STLB shared based on the dynamic activity of each thread or are they partitioned evenly so each thread gets exactly 50% of the entries?
2. Does hyperthreading on Sandy Bridge have any improvements compared to previous processor generations? In particular, does Sandy Bridge reduce the cases where enabling hyperthreading reduces performance?
3. Is there any operating system that lets an administrator enable or disable hyperthreading without going into the BIOS and rebooting the machine? Is there something about the hardware that makes this impossible?