One of the things that caused the most complaints Windows 11 are its high feature-level system requirements, although unofficially (supposedly) they can be skipped. However, the change introduced in the future Windows 11 24H2 aims to make it impossible to install on very old computers, since the latest major version of the system officially works even on Pentium 4 (Microsoft and its stuff).

The reason Windows 11 24H2 may not work on very old computers is because Microsoft included a requirement that the processor support the POPCNT instruction if the operating system is to be booted. This was posted by X Bob Ponywho, according to his version, found that the said instruction was required in build 25905.

Without going into depth, POPCNT is an instruction that calculates the number of bits set 1 to 16, 32, and 64-bit unsigned integers. When a variable of type integer is unsigned, it means that all bits of the string are used to represent numbers that are zero or positive, resulting in a larger maximum amount that can be represented positively (from 0 to 4,294,967,295 in programming language C with a 32-bit integer).

AMD introduced POPCNT instruction support in 2006-2007 with its Barcelona architecture, while Intel did the same with Nehal.the first generation of the family Core i. This requirement makes it impossible to run Windows 11 build 25905 on older processor models, such as those from the AMD Turion II and Intel Core 2 Duo families, even when using steps to bypass the official requirements. Microsoft’s reasons for this move are not yet known, but information circulating suggests that some operating system functions rely on POPCNT instructions.

Given the precedents set by Windows 11, this new restriction will have a tail, even if it does not apply to any officially compatible computer and only hurts very old computers that require tricks to make the system work (come on, they are officially not compatible). What’s more, if the intention is to use these computers for production, the most sensible thing to do would be to use a Linux distribution with optimized software, such as Debian or MX Linux.

Another debate that can be raised is whether supporting very old processors will cause the most modern ones to not be properly used.