The POP4.2 application bypasses Windows 11 processor checks, allowing installation on many older, unsupported processors.
Earlier this week, Microsoft released the latest feature release of Windows, Windows 11 build 26H2, to the general public. You can get ISO files for a clean install or upgrade of your existing system, or jump straight to the new version using the necessary activation package in just a few minutes.
For those running unsupported systems, there is the option to upgrade to Windows 11 26H2 using third-party applications such as Rufus . However, Microsoft had completely blocked certain processors from running on Windows 11 when it released version 24H2 two years ago. The company made SSE4.2 and PopCnt instructions mandatory for processors (otherwise the installation stops from the beginning), and until now there was no way to bypass this restriction.
But now a third-party utility called POP4.2 has been released. The application allows systems to bypass this limitation on Windows 11 24H2 and 25H2, and has been updated to work on Windows 11 26H2. The application's creator says that the tool works on processors that have PopCnt but lack SSE4.2.
Because the SSE4.2 instruction does not appear to be utilized in most Windows files, the tool allows the installation of Windows 11 26H2 on processors that support at least the PopCnt instruction (which is part of the SSE4a instruction set).
Here is a picture of Windows 11 25H2 running on an Athlon II X2 M320:
The developer states:
“Although Windows 11 checks for both POPCNT and SSE4.2, it doesn’t actually require SSE4.2 for 99% of its files, with a few exceptions that can be bypassed (read below). To enforce this restriction, Microsoft uses the undocumented RtlDetectProcessorFeatures function and checks for the requirements by reading data from the .rdata section. In kernel 26100.7171, this is located at offset 00000001400088C0 and contains the bytes 01 00 00 00 00 00 00 00 00 00 00 10 00 02 00 00 00 0D 00 00 00 in the IDA. To bypass this, we simply change 0D to 0C, instructing Windows to essentially skip the check and continue the boot process."
Essentially, the developer used the Interactive Disassembler (IDA) for reverse engineering in order to understand Microsoft's blocking mechanism. The developer loaded the Windows kernel (ntoskrnl.exe) into IDA to convert the raw machine code into human-readable assembly language.
This allowed him to map the file's memory structure, pinpoint the exact point where Windows verifies the processor's hardware requirements, and then modify specific bytes to bypass the strict compatibility checks. POP4.2 creator Smu1zel teamed up with X user and Windows friend Bob Pony to test the application on the latter's AMD Phenom X4 9600 processor, a 2008 quad-core processor based on AMD's K10 microarchitecture.
Watch the video guide below from Bob Pony (be careful with the volume):
You can find the POP4.2 tool in its official GitHub repository . The page includes detailed instructions for your convenience.
However, the application has some known limitations that the developer warns about. In particular, Nvidia nForce chipsets, which were very widespread at the time, may experience "freezing" or malfunctioning. Also, the popular Intel Core 2 processors are unfortunately not supported, as they lack support for the SSE4a instruction set.
Although the press releases will range from very select to rare, I said I'd pass...because sometimes the editors hide.
