Home windows 11 24H2 goes from “unsupported” to “unbootable” on some older PCs

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By Calvin S. Nelson

Enlarge / We have put in Home windows 11 on techniques as previous as this Core 2 Duo Inspiron tower. As of model 24H2, the OS could now not be bootable on these techniques.

Andrew Cunningham

Formally, Home windows 11 has increased system necessities than Home windows 10. However so far, as soon as you’ve got bypassed these requirement checks, there have been few penalties to operating Home windows 11 on previous {hardware}. Unsupported or not, Home windows 11 would run on just about any 64-bit PC that might boot Home windows 10—we have run it on PCs as previous as a Home windows XP-era Core 2 Duo desktop.

That is apparently altering a bit in Home windows 11’s 24H2 replace, which Microsoft started testing earlier this month. In accordance with posts from a person named Bob Pony on X, previously Twitter, the newest Home windows 11 builds refuse besides on older processors that do not help a comparatively obscure instruction referred to as “POPCNT.” Brief for “inhabitants depend,” it is used for “counting the variety of bits in a machine phrase,” in accordance with an explainer by programmer Vaibhav Sagar.

It is unclear why POPCNT has grow to be the load-bearing CPU instruction for an entire bunch of Home windows elements, however it appears like the Home windows kernel, the system’s USB and community drivers, and different core system information now require the instruction as of Home windows 11 24H2.

In trendy x86 CPUs, POPCNT is carried out as a part of the SSE4 instruction set. For Intel’s chips, it was added as a part of SSE4.2 within the authentic first-generation Core structure, codenamed Nehalem. In AMD’s processors, it is included in SSE4a, first utilized in Phenom, Athlon, and Sempron CPUs based mostly on the K10 structure. These architectures date again to 2008 and 2007, respectively.

That successfully bars mid-2000s Intel Core 2 Duo techniques and early Athlon 64-era PCs from booting Home windows 11 in any respect, not that they formally supported it within the first place. This implies the change ought to primarily have an effect on retro-computing fans who spend their days making YouTube movies within the “we put in Home windows 11 on a potato, let’s have a look at the way it runs” style slightly than customers of precise techniques. Even in the event you upgraded these PCs with 4 or 8GB of RAM and adjusted out the creaky previous laborious drives for SSDs, these are usually not PCs that can run Home windows 10, Home windows 11, or any trendy apps notably properly.

These similar retro-computing fans may discover a means round this requirement finally. Home windows 10 and 11 will not boot on techniques with out SSE2 help, for instance, however that hasn’t stopped individuals from discovering a solution to do it anyway.

Although Home windows 11’s system necessities counsel CPU clock pace and the quantities of RAM and storage your PC has, system necessities within the trendy period have grow to be extra granular and esoteric. For instance, it appears as if Home windows 11’s CPU requirement (an Eighth-gen Intel Core CPU or newer, or an AMD Ryzen 2000-series CPU or newer) is pushed not less than partly by help for “mode-based execution management” (MBEC), a safety function that accelerates a number of the working system’s reminiscence integrity protections. No CPU producer is together with stuff like POPCNT or MBEC of their advertising supplies, however trendy Home windows help is more and more dictated by these sorts of options.

Itemizing picture by Microsoft

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