Microsoft’s long‑promised fix for running legacy PC games and x86 apps on Arm‑based Copilot+ laptops has finally landed in a monthly cumulative patch — and for many users the change could be the difference between a shelfbound novelty and a genuinely useful Windows alternative. The October cumulative (delivered as KB5066835 for Windows 11 24H2 and 25H2) expands Prism — the Windows on Arm emulator — so that it can advertise and emulate important x86‑64 vector extensions such as AVX and AVX2, plus related sets like BMI, FMA and F16C. That single engineering move opens the door for a large swath of games and pro apps that until now simply refused to run on Snapdragon‑powered Copilot+ machines.
Since Microsoft and Qualcomm rolled out the first wave of Copilot+ PCs, adoption has been held back by a compatibility problem baked into the very nature of the hardware: modern Windows software was written for the x86/x64 instruction set used by Intel and AMD, while Snapdragon chips use Arm microarchitecture. Microsoft’s new emulator, Prism, is the company’s answer — a JIT (just‑in‑time) translation layer included with Windows 11 24H2 that translates x86/x64 code to Arm64 at runtime and caches translated blocks for later use. Prism was introduced in Insider channels in 2024 and has been iterated since; the October retail cumulative (KB5066835) is the first broad release that exposes emulated CPU features to applications in a way that bypasses a frequent class of “won’t run” checks.
Why does that matter for gamers? Many modern game engines and multimedia libraries check for and rely on Advanced Vector Extensions (AVX/AVX2) — SIMD instructions that let CPUs perform multiple floating‑point operations in parallel. When a game detects no AVX support it may refuse to launch or pick a disabled code path; without AVX the game’s physics, encoders, or critical math routines might be compiled only for x86 targets and thus fail. Emulating those instruction sets addresses a fundamental compatibility blocker for titles that never received native Arm64 builds.
This update also aligns with Qualcomm’s next‑gen roadmap. Qualcomm has publicly introduced a follow‑up chipset family (the Snapdragon X2 series), promising significant single‑ and multi‑core gains plus much larger NPUs for on‑device AI; those chips — and the first systems built around them — are expected to hit the market in the first half of 2026. Microsoft’s Prism work is optimized to leverage specific hardware features in some Snapdragon X silicon, so Prism improvements and Qualcomm’s silicon roadmap are complementary moves.
Apple has since announced a timeline to scale back Rosetta: Apple told developers at WWDC 2025 that full Rosetta support will be available through macOS 27, and that macOS 28 (expected in 2027) will only retain a subset of Rosetta functionality aimed at supporting some older games. That decision shows how even Apple—and its once‑smooth transition—now plans an eventual hard break as the ecosystem finishes porting to Arm. Microsoft’s task is harder precisely because Windows must support a far wider mix of hardware and third‑party drivers while carrying a much larger legacy application base.
But it is a milestone, not a finish line. Emulation reduces barriers; it does not erase the performance, driver, and anti‑cheat hurdles that define high‑end PC gaming. For those who bought Copilot+ devices and were frustrated by the early limitations, Prism’s new emulation features materially improve the product’s promise. For buyers considering these machines now, the sensible path is to test the specific games and apps you care about, keep expectations realistic about performance, and watch for publisher and anti‑cheat confirmations before treating these laptops as drop‑in replacements for native x86 gaming rigs.
Where Apple’s Rosetta 2 made a clean, user‑friendly transition for many Mac users — at the cost of a tightly controlled hardware and software stack — Microsoft’s route must accommodate a fragmented, heterogeneous Windows ecosystem. Prism’s AVX/AVX2 emulation is the right technical move, and when paired with next‑gen Snapdragon X2 hardware and vendor driver maturity, it could finally make gaming on Copilot+ PCs stop being a compromise and start being a practical option for more people. Until then, this update is best read as a turning point rather than a triumphant finish — a big, welcome step toward usable compatibility that still depends on follow‑through from hardware vendors, publishers, and middleware vendors to realize its full promise.
Source: Gizmodo Gaming Is Gonna Suck a Whole Lot Less on Copilot+ PCs
Background / Overview
Since Microsoft and Qualcomm rolled out the first wave of Copilot+ PCs, adoption has been held back by a compatibility problem baked into the very nature of the hardware: modern Windows software was written for the x86/x64 instruction set used by Intel and AMD, while Snapdragon chips use Arm microarchitecture. Microsoft’s new emulator, Prism, is the company’s answer — a JIT (just‑in‑time) translation layer included with Windows 11 24H2 that translates x86/x64 code to Arm64 at runtime and caches translated blocks for later use. Prism was introduced in Insider channels in 2024 and has been iterated since; the October retail cumulative (KB5066835) is the first broad release that exposes emulated CPU features to applications in a way that bypasses a frequent class of “won’t run” checks. Why does that matter for gamers? Many modern game engines and multimedia libraries check for and rely on Advanced Vector Extensions (AVX/AVX2) — SIMD instructions that let CPUs perform multiple floating‑point operations in parallel. When a game detects no AVX support it may refuse to launch or pick a disabled code path; without AVX the game’s physics, encoders, or critical math routines might be compiled only for x86 targets and thus fail. Emulating those instruction sets addresses a fundamental compatibility blocker for titles that never received native Arm64 builds.
What KB5066835 and Prism actually change
The engineering at a glance
- Prism now advertises AVX/AVX2 and several related x86 extensions to x64 apps running under emulation. That means apps that probe CPU feature bits will see the expected extensions and may proceed to initialize code paths they previously refused to use.
- Emulation is implemented via JIT translation and cached translated blocks. Windows translates hot x86/x64 code to Arm64, caches it per module, and reuses that translation on subsequent launches to reduce overhead.
- Target scope is x64 (64‑bit) applications. 32‑bit apps and installers that rely on 32‑bit helpers or legacy detection logic may still fail to recognize the new emulated features. This is a meaningful limitation in many older titles and tool chains.
- System / per‑executable controls: Windows exposes compatibility toggles — you may see a new checkbox in an app’s Properties > Compatibility page labeled along the lines of “Show the latest emulated CPU features.” Users can enable these per executable if the system hasn’t globally enabled the new features.
What this does not magically fix
- Emulating AVX/AVX2 does not make an ARM laptop as fast as a similarly spec’d x86 laptop running the same native code. Emulation incurs overhead and some high‑frequency vector workloads will be CPU‑bound and slower. Real‑world performance varies widely by title and how much of the work is CPU SIMD versus GPU or other bottlenecks. Independent testing so far shows many games will now launch, but playability and FPS are title‑dependent.
- Anti‑cheat, GPU drivers, and kernel‑mode drivers remain friction points. Some anti‑cheat stacks and vendor drivers expect x86 environment characteristics and can still block or crash. The emulator’s feature expansion reduces one class of blockers but does not eliminate driver or anti‑cheat incompatibilities.
Why this matters for Copilot+ PCs and gaming
Copilot+ PCs were pitched as AI‑forward, battery‑friendly Windows devices — often using Qualcomm’s Snapdragon X family — but early buyers quickly hit a compatibility wall. Many legacy apps and games either didn’t run or were so crippled they were unusable, and early returns and complaints became part of the story. With Prism now able to emulate AVX/AVX2, buyers finally have a path to running titles that were previously blocked; popular, high‑profile games (reported in preview testing) like big AAA releases that used AVX2 could now at least launch under emulation. That immediately widens the software catalog for Arm laptops and reduces the “island” effect that left many Copilot+ devices appealing only on spec sheets.This update also aligns with Qualcomm’s next‑gen roadmap. Qualcomm has publicly introduced a follow‑up chipset family (the Snapdragon X2 series), promising significant single‑ and multi‑core gains plus much larger NPUs for on‑device AI; those chips — and the first systems built around them — are expected to hit the market in the first half of 2026. Microsoft’s Prism work is optimized to leverage specific hardware features in some Snapdragon X silicon, so Prism improvements and Qualcomm’s silicon roadmap are complementary moves.
Apples and oranges: Why the Apple transition looked smoother
Apple’s 2020 transition to M‑series chips included Rosetta 2, a translation layer built into macOS that allowed the majority of Intel apps to run on Apple Silicon with minimal user involvement. The experience often “just worked,” because Apple controlled both OS and hardware, tightly optimized Rosetta early, and curated transition messaging. Microsoft’s Windows ecosystem is vastly broader, multiple OEMs ship wildly different drivers and firmware, and the Windows software base is more heterogeneous — all of which complicated Microsoft’s work in delivering a similarly seamless compatibility story.Apple has since announced a timeline to scale back Rosetta: Apple told developers at WWDC 2025 that full Rosetta support will be available through macOS 27, and that macOS 28 (expected in 2027) will only retain a subset of Rosetta functionality aimed at supporting some older games. That decision shows how even Apple—and its once‑smooth transition—now plans an eventual hard break as the ecosystem finishes porting to Arm. Microsoft’s task is harder precisely because Windows must support a far wider mix of hardware and third‑party drivers while carrying a much larger legacy application base.
Deep dive: How AVX/AVX2 emulation helps — and when it won’t
The good
- Launch blockers removed: Many apps that previously refused to start because of AVX checks will now pass those checks and proceed. That’s a practical win: the program gets further into execution where other compatibility layers or fallbacks can kick in.
- Pro‑app support improves: Professional creative tools that rely on vectorized code paths (e.g., some video encoders and filters) are more likely to run, increasing the usefulness of Copilot+ systems to creators who were previously limited to cloud‑only workflows.
- Per‑app control minimizes surprise: Windows exposes compatibility flags so power users and support teams can enable emulated features on a per‑executable basis while leaving the global default conservative during the wider roll‑out.
The limits and the real‑world caveats
- Performance penalty is unavoidable with emulation. AVX2 operations are vectorized for native x86 silicon and may run substantially slower when JIT‑translated to Arm64, depending on how hot those codepaths are and whether the emulator can optimize the workload well. Until independent benchmarks across a wide library of games appear, precise performance expectations should be conservative. Treat "it runs" as a baseline success, not as a claim of parity with native x86.
- 32‑bit and mixed installers remain a problem. Many older games and installers ship with 32‑bit components or use legacy detection routines; Prism’s AVX emulation targets x64 apps and won’t necessarily fix those scenarios. That means a non‑trivial catalog of titles could still be stuck.
- Anti‑cheat and DRM compatibility is still on publishers and middleware. Some anti‑cheat kernels are highly sensitive to environment mismatches and may fail or block under emulation. Until anti‑cheat vendors explicitly certify compatibility, expect some online titles or competitive games to remain off‑limits.
- GPU and driver ecosystem matters more than ever. GPU driver maturity on Arm Windows devices can be a bottleneck. If an emulator allows a game to launch but the GPU driver lacks feature parity or stable performance, the experience will still be poor.
Practical steps: How to test and enable Prism AVX emulation on your Copilot+ PC
- Install Windows updates: ensure your Copilot+ PC is updated to Windows 11 24H2 or 25H2 and has the October cumulative (KB5066835) installed. (Windows Update will show the cumulative; check Settings → Windows Update.)
- Verify OS build: some guides mention minimum build numbers tied to rollout channels; stay on retail release builds rather than early Canary/Insider channels unless you’re prepared for additional instability.
- Per‑executable enablement:
- Right‑click the app’s .exe → Properties → Compatibility.
- Look for an option such as “Show the latest emulated CPU features” and toggle it on if present.
- If the checkbox reads “Hide latest features,” the system likely has global emulation enabled already.
- Update GPU drivers and vendor control panels: use OEM or silicon vendor driver packages when available (check Qualcomm/OEM driver sites and Windows Update drivers). If the title uses vendor runtime components (Vulkan/DX), update those as well.
- Test with single‑player titles first: avoid competitive or online play until anti‑cheat and publisher statements confirm safe use. Use FPS and telemetry tools to compare performance with and without the new emulation flags.
Cross‑checked facts and what’s verified
- Microsoft released a cumulative update that expands Prism’s emulated CPU features to include AVX and AVX2 (among others) in the October cumulative KB5066835 for Windows 11 24H2/25H2. This behavior was observed rolling out from Insider builds earlier and now into retail channels.
- The change targets x64 applications; legacy 32‑bit detection and mixed 32/64 installers may still fail to see those emulated features.
- Early reporting and community testing show many previously blocked titles will now launch under Prism, but performance and full playability vary by title, and anti‑cheat/driver issues remain potential blockers.
- Apple intends to scale back Rosetta 2 availability after macOS 27; the comparison between Microsoft’s and Apple’s transitions is instructive but not numerically identical given Apple’s tight hardware+software control.
Strategic analysis: strengths, risks and what Microsoft should have done
Strengths of Microsoft’s current approach
- Practical compatibility wins: Emulating AVX/AVX2 removes a deterministic “won’t run” class of bugs and vastly increases the number of titles that will at least reach runtime on Arm laptops. That’s a real win for user experience.
- Incremental deployment: Exposing per‑EXE toggles and keeping the roll‑out inside a cumulative update lets Microsoft test widely while limiting surprise breakage for the general install base.
- Hardware synergy: The work is timed to dovetail with Qualcomm’s second‑generation Snapdragon X2 silicon, which promises higher CPU/GPU and NPU performance; better silicon plus better emulation makes a more compelling overall story.
Risks and execution gaps
- Performance expectations management: Marketing that implies parity with Intel/AMD in gaming will be damaging if community benchmarks consistently show significant slowdowns in AVX‑heavy tasks. Microsoft and OEMs must set realistic expectations.
- Anti‑cheat and driver dependency: Microsoft cannot unilaterally “fix” anti‑cheat problems; publishers and middleware vendors must certify support. Until that happens, many competitive and popular online titles will remain risky.
- Fragmented Windows ecosystem: Unlike Apple’s controlled transition, Microsoft depends on a wide array of driver vendors and OEMs to ship mature drivers and firmware. That fragmentation slows the “it just works” moment that Rosetta 2 delivered for many Mac users.
- Late communications and buyer confusion: Many early Copilot+ buyers felt under‑informed about the practical software limits of Arm Windows devices. Microsoft and OEMs should have communicated clearer compatibility roadmaps and feature gates when devices launched. That reputational hit could dampen adoption even if Prism succeeds technically.
Quick checklist for buyers and IT managers
- If you rely on a specific game or application, wait for a community or publisher confirmation that the title runs acceptably under Prism before switching your primary system to an Arm device.
- For trialists: update to KB5066835, enable per‑app emulation where necessary, update drivers, and run controlled benchmarks comparing native x86 machines.
- For enterprise: treat Copilot+ PCs as a niche/secondary deployment option until anti‑cheat/driver and application vendor compatibility lists are validated for your critical software.
- Keep a fallback plan: make sure your workflows are deployable on both x86 and Arm devices, or use cloud‑hosted instances for heavy tasks until native Arm support matures.
Looking ahead: what to watch next
- Independent benchmarking reports that measure frame rates, CPU utilization, and power consumption for AVX/AVX2‑heavy games under Prism vs. native x86. Those numbers will determine whether Copilot+ is a viable gaming platform or simply a compatibility band‑aid.
- Anti‑cheat vendor statements and publisher compatibility lists. Titles with kernel‑mode anti‑cheat are the ones most likely to remain blocked; any publisher certifications will unlock mainstream gaming viability.
- OEM driver rollouts and firmware updates timed with Snapdragon X2 systems shipping in early 2026. Driver maturity and thermal/power tuning will shape the real gaming experience more than the emulation layer alone.
- Developer engagement: whether major middleware and engine vendors ship optimized Arm64 builds or at least test and certify their Windows titles for Prism emulation. The broader the native/official support, the less emulation will be relied on.
Conclusion
Microsoft’s Prism update in KB5066835 is a significant, pragmatic step toward making Windows on Arm — and specifically Copilot+ PCs using Snapdragon silicon — much more usable for everyday users who want the full catalog of Windows software. For the first time, a common, centuries‑old source of “this won’t run on Arm” errors (AVX/AVX2 checks) can be meaningfully mitigated on retail systems. That’s a milestone worth celebrating.But it is a milestone, not a finish line. Emulation reduces barriers; it does not erase the performance, driver, and anti‑cheat hurdles that define high‑end PC gaming. For those who bought Copilot+ devices and were frustrated by the early limitations, Prism’s new emulation features materially improve the product’s promise. For buyers considering these machines now, the sensible path is to test the specific games and apps you care about, keep expectations realistic about performance, and watch for publisher and anti‑cheat confirmations before treating these laptops as drop‑in replacements for native x86 gaming rigs.
Where Apple’s Rosetta 2 made a clean, user‑friendly transition for many Mac users — at the cost of a tightly controlled hardware and software stack — Microsoft’s route must accommodate a fragmented, heterogeneous Windows ecosystem. Prism’s AVX/AVX2 emulation is the right technical move, and when paired with next‑gen Snapdragon X2 hardware and vendor driver maturity, it could finally make gaming on Copilot+ PCs stop being a compromise and start being a practical option for more people. Until then, this update is best read as a turning point rather than a triumphant finish — a big, welcome step toward usable compatibility that still depends on follow‑through from hardware vendors, publishers, and middleware vendors to realize its full promise.
Source: Gizmodo Gaming Is Gonna Suck a Whole Lot Less on Copilot+ PCs
