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primemixxx targets the Denon Prime Go and Prime 4, both of which share a Rockchip RK3288 ARMv7 SoC running a stripped-down Buildroot Linux environment beneath Engine OS. The two devices are nearly identical at the hardware level, but their display controllers differ in a way that currently limits Prime 4 support. This page covers the compatibility status, shared hardware specifications, and the display differences that determine what works on each device.

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Compatibility Summary

Prime Go

✅ Fully VerifiedDisplay, audio, touchscreen, and all MIDI controls are functional. MIXXX runs natively on the LVDS-1 display at 1280×800. Audio latency: 5.8 ms.

Prime 4

⚠️ Partial SupportMIXXX boots and all audio/MIDI controls work. The DSI-1 display causes a GPU crash on EGL initialization — MIXXX currently runs in offscreen mode with no on-device display output.
FeaturePrime GoPrime 4
MIXXX boots✅✅
Audio output✅✅
MIDI controls (platters, faders, pads)✅✅
Touchscreen input✅✅
On-device display✅⚠️ Offscreen only
Verified stable at 5.8 ms✅Not tested

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Shared Hardware Specifications

Both devices use the same core hardware platform.
ComponentDetail
SoCRockchip RK3288 ARMv7 (Cortex-A17, 4 cores)
GPUMali-T76x (4 cores, r1p0 0x0750)
Kernel6.1.111-inmusic-2024-09-19-rt41 with PREEMPT_RT
OSStripped Buildroot Linux — no X11, no Wayland
Display7-inch touchscreen, 800×1280 portrait physical framebuffer, rotated to 1280×800 landscape by display controller
TouchscreenILI2117 on /dev/input/event0
AudioXMOS XS1-U6A USB audio controller → AKM AK4621 CODEC + AK4413 DAC
MIDIInternal USB MIDI — platters, faders, pads, encoders, crossfader all exposed

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Why PREEMPT_RT

The kernel ships with full real-time preemption (CONFIG_PREEMPT_RT), which guarantees that audio threads cannot be blocked by kernel syscalls. MIXXX’s audio engine threads run at SCHED_FIFO priority 98, pinned to CPU cores 2–3. Without PREEMPT_RT, any syscall in the kernel path could block the audio thread and cause dropouts. The result is a stable 5.8 ms (256/512 ALSA buffer) on the Prime Go.

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CPU Shielding

primemixxx applies aggressive CPU isolation at launch time:
  • Audio-critical threads (EngineWorkerSch, EngineSideChain): SCHED_FIFO priority 98, pinned to cores 2–3
  • Non-audio threads (Mali GPU, touchscreen, CachingReader, Qt thread pool, GLib): SCHED_OTHER, banished to cores 0–1
  • Main thread: SCHED_FIFO priority 1 on cores 2–3 (low-RT for MIDI and UI events)
  • IRQ affinity: all non-audio IRQs (GPU, USB, MMC) pinned to CPU 0 at boot

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Per-Device Details

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Prime Go

The Prime Go is the fully verified target. All hardware features work with primemixxx.
  • Display connector: LVDS-1
  • Native resolution: 800×1280 portrait framebuffer, rotated to 1280×800 landscape by the display controller
  • EGLFS rotation: 90°
  • Touchscreen: ILI2117 on /dev/input/event0, calibrated to the rotated landscape orientation
  • Audio latency: 5.8 ms (256/512 ALSA buffer) with CPU shielding enabled
  • MIDI: All controls exposed — platters, channel faders, EQ knobs, trim, pads, transport buttons, crossfader, browse encoder, DJ FX section
  • USB Ethernet gadget: auto-starts at boot, device accessible at 192.168.42.1
The Prime Go’s LVDS-1 display is directly compatible with the Mali EGLFS integration plugin compiled into the SD card bundle. Qt 5.15.8 takes over the display from fbcon cleanly, and the custom libqeglfs-mali-integration.so renders MIXXX’s UI at full resolution without tearing.

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Prime 4

The Prime 4 shares the same SoC, audio hardware, and MIDI layout as the Prime Go, but uses a DSI-1 display interface instead of LVDS-1.
DSI display causes GPU crash on EGL init. The Prime 4’s DSI-1 display is not compatible with the current Mali EGLFS stack. MIXXX segfaults during EGL initialization when run with the standard eglfs platform. To verify that MIXXX itself works, run it with -platform offscreen. Audio and MIDI are fully functional in offscreen mode — only the display output is missing. Native DSI display support requires further investigation into the DDK/DSI interface.
  • Display connector: DSI-1
  • Current display support: Offscreen mode only (-platform offscreen)
  • Audio: Functional (same XMOS/AKM hardware chain as Prime Go)
  • MIDI: Functional (same internal USB MIDI layout as Prime Go)
  • EGLFS rotation: 270° (differs from Prime Go)

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Prime Go vs Prime 4 Differences

PropertyPrime GoPrime 4
Display interfaceLVDS-1DSI-1
EGLFS rotation90°270°
Display vsyncStandardIncompatible with current EGL stack
MIXXX display output✅ Native 1280×800⚠️ Offscreen only
Audio✅ Functional✅ Functional
MIDI✅ Functional✅ Functional
Touch✅ Functional✅ Functional
Verified latency5.8 msNot yet tested
Engine OS internal IDPRIMEGO (JP11)PRIME4 (JC11)

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Audio Hardware Chain

Both devices route audio through the same hardware stack: 
MIXXX (ALSA) → XMOS XS1-U6A USB audio controller
                  → AKM AK4621 CODEC    (ADC + DAC, main outputs)
                  → AKM AK4413 DAC      (additional output channels)
The XMOS controller presents as a standard USB audio device to the Linux kernel, which means ALSA sees it as a class-compliant interface. No custom kernel driver is required.

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Mali GPU Notes

The device’s Mali-T76x GPU is hardware revision r1p0. Buildroot’s default Mali DDK ships as r0p0, which causes EGL initialization to fail with: 
DDK is not compatible with hardware: DDK version r0p0 0x0720, hardware version r1p0 0x0750
primemixxx works around this by symlinking the bundle’s libEGL.so, libGLESv2.so, and libGLESv1_CM.so to the device’s native /usr/lib/libmali.so.14.0 (r1p0). This is done automatically by the SD card bundle — no manual intervention is required on the Prime Go. On the Prime 4, the same symlinks are applied, but the DSI-1 display interface introduces a second incompatibility that is not yet resolved.

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