Metal on AMD Radeon 780M for macOS Tahoe.
GPU bring-up, a display driver WindowServer composites on, and Metal over Vulkan (Mesa RADV)
for Phoenix / Hawk Point APUs (RDNA 3, GC 11.0.1, gfx1103).

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Status

Measured on the reference machine — Firebat U6C, Ryzen 7 H 255, Radeon 780M, 2560×1600 120 Hz eDP, macOS Tahoe 26.6.2 — in October 2026:

Desktop	WindowServer composites on the 780M at the panel's 120 Hz. CoreAnimation runs at 119–120 fps; dragging a window, 116 fps.
Liquid Glass	Dock, widgets, Control Center and in-app glass are drawn by the GPU with Apple's own compositor shaders (translated).
Metal in apps	Every process gets the Metal device, sandboxed WebKit GPU processes included. About 46 apps checked with no crashes, Safari, Chess and Spotify among them.
Display sleep / wake	Works.
First use of a new effect	A one-time pause of about 1–3 s while its shader is translated and compiled. After that it comes from the disk cache.
Not yet	External displays (HDMI, USB-C), hardware video decode/encode, backlight control.

Other Radeon 780M / 760M machines (Phoenix, Hawk Point) are untested.

How it works

flowchart TD
  apps["Apps · WindowServer"] -->|Metal| plugin["NVMTLDriver.bundle<br/>Metal objects on Vulkan"]
  plugin -->|"AIR → SPIR-V"| xlate["libnvmtl_translate"]
  plugin -->|Vulkan| radv["Mesa RADV<br/>libvulkan_radeon.dylib"]
  plugin -->|IOAccelerator| accel["PhxAccel.kext<br/>NMXAccel · PhxAMDFB · PhxAGDC"]
  radv -->|"IOKit user client"| bringup["PhxBringup.kext<br/>PSP · MES · GPUVM"]
  bringup --> gpu[("Radeon 780M")]
  accel -->|scan-out| panel["eDP panel · DCN 3.1.4"]

Loading

Component	Installed in	Source	Role
PhxBringup.kext	OpenCore EFI/OC/Kexts	src/phxbringup	Loads firmware through the PSP, powers up GFX (SMU/IMU), starts the MES scheduler and the compute and graphics queues, gives every process its own GPUVM address space, implements the BO/submit ABI RADV uses.
PhxAccel.kext	Auxiliary kernel collection	src/phxaccel	NMXAccel IOAccelerator, the PhxAMDFB framebuffer (VRAM pool, 120 Hz vblank, frame copy to scan-out) and PhxAGDC display control.
NVMTLDriver.bundle	/System/Library/CoreServices/CoreTypes.bundle/Contents/Library/PhxGPU, linked from /Library/GPUBundles	src/nmplugin	The Metal driver plugin: Metal on Vulkan, zero-copy IOSurfaces, shader caches.
libvulkan_radeon.dylib	PhxGPU/nvmtl	Mesa + mesa-patches-phoenix	RADV for gfx1103 with a Darwin winsys.
phxboot	LaunchDaemon local.phxboot	tools/phxctl/phxboot.sh	Brings the GPU up at boot before WindowServer opens the panel, with fail-safes that fall back to the firmware framebuffer.

libnvmtl_translate.dylib (Metal AIR → SPIR-V, LGPL-3.0, based on metal2vulkan) ships prebuilt with NullMoth's plugin; its source is attached to every release. The NVMTL prefix is NullMoth's too: none of this is an NVIDIA driver.

Installing

Download nullarc-<version>.zip from the releases page and follow docs/INSTALL.md. In short: add PhxBringup.kext and the boot-args to OpenCore, reboot, run sudo ./install.sh --windowserver from the release folder, reboot twice.

Warning

WindowServer only loads an ad-hoc signed driver with AMFI relaxed (amfi=0x80, amfi_get_out_of_my_way=0x1). That turns library validation off system-wide and FairPlay playback (Apple TV+, Netflix in Safari) stops working. uninstall.sh and the guide's last section undo everything.

Building

On the Mac (Command Line Tools, MacKernelSDK):

sh src/phxbringup/build.sh /path/to/MacKernelSDK      # PhxBringup.kext
sh src/phxaccel/build.sh /path/to/MacKernelSDK        # PhxAccel.kext

The plugin builds from src/nmplugin/NVMTLDevice.m, which includes the rest of src/nmplugin. RADV: Mesa f5cb8ee0 + Cobalt64's Darwin patches + mesa-patches-phoenix.

Unit tests (firmware parsing, IP discovery) run on Linux or macOS and in CI:

make fixtures   # Phoenix firmware from linux-firmware
make test

Notable fixes

• Zero-copy IOSurfaces — textures are linear images over the surface's own pages; WindowServer CPU 77 % → 36 %.
• Surface keep cache — CoreAnimation re-wraps the same IOSurfaces every frame; keeping their imports took a dragged window from 64–69 to 116 fps.
• VRAM pool — per-allocation contiguous memory fragmented after hours and display wake froze; one 512 MB pool now.
• RADV mutable descriptor lists — indexed by the sorted binding order instead of the original one; broke CoreImage blurs and Tahoe's layered icons.
• Nested loop unrolling (Mesa 0006) — a new compositor shader variant compiled ~2 s in RADV, one loop level per optimisation round; now ~1 s with identical code.

The name

null + arc: the empty-set sign of a driver that did not exist, its ring opened into an arc. See the brand guide.

License and credits

Several licenses apply; see LICENSE, THIRD_PARTY_NOTICES.md and LICENSES/.

• Code written for nullarc (src/phxbringup, tools/phxctl, …): MIT, or GPL-2.0-only at your option.
• src/phxaccel, src/nmplugin, tools/nvmtl-patches: derived from NullMoth's macOS driver, PolyForm Noncommercial 1.0.0 — no commercial use.
• mesa-patches-phoenix: MIT, as Mesa. Release packages also carry LGPL-3.0 (shader translator), LLVM and AMD firmware; see the notices.

Built on the work of the Linux amdgpu team, Mesa, NullMoth, Cobalt64, Acidanthera and the AMD-OSX community.