Microsoft tests Windows 11 APX toggle for future hardware

Microsoft is testing a new "Advanced Performance Extensions" toggle in Windows 11 Insider Preview Build 29695.1001, released on October 23. The setting, labeled "Let Windows use APX for better performance," appears under Settings > System > Advanced as a developer feature. Enabling the option requires a system restart.

APX is an extension to the x86-64 instruction set developed by Intel. It raises the general-purpose register count from 16 to 32. Intel says this allows compilers to keep more values in registers rather than moving them to and from memory. Intel estimates that code compiled with APX contains 10% fewer loads, more than 20% fewer stores, and about 10% fewer instructions than code built for the existing x86-64 baseline. These figures come from prototype simulations using SPEC CPU 2017 integer workloads and do not guarantee the same performance gains in real applications.

The toggle will not provide any speed increase for current processors because APX requires hardware-level changes. For a performance benefit, users will need both compatible CPUs and software recompiled to use the new instructions. Intel says most code should only require a rebuild without needing source code changes.

Intel's Diamond Rapids Xeon line is expected to be the first target for APX. On the consumer side, Intel's upcoming Nova Lake processors are expected to support the extension. Reports say AMD is also expected to adopt APX, though AMD has not officially confirmed this and no specific Ryzen models have been named. Microsoft has not said when this feature will move to standard Windows 11 releases.