iMac Late 2013

iMac Late 2013

The Apple iMac Late 2013 with NVIDIA graphics (iMac14,2 27-inch or iMac14,3 21.5-inch) uses the general ISO, couchliteos-<version>-amd64.iso. It detects the iMac at every boot and loads the right drivers. The NVIDIA ISO also works (it falls back to the same open driver) but only adds size.

The 21.5-inch iMac14,1 has Intel Iris Pro graphics instead; the general ISO supports it like any Intel PC, and the notes below do not apply.

Boot

1. Write the ISO to a USB stick (Install).
2. Plug it into a rear USB port, connect Ethernet if you can, and power on while holding Option (⌥).
3. Choose the yellow EFI Boot entry. This iMac has no Secure Boot, so nothing needs to be turned off.
4. CouchLiteOS starts after three seconds at the panel's native resolution.

Installing to the internal disk erases macOS. Many of these iMacs have a Fusion Drive (a separate SSD and hard disk): choose the target disk carefully.

How the hardware is handled

Part	Handled by
NVIDIA Kepler GT 750M / GT 755M / GTX 775M / GTX 780M	Open nouveau driver. NVIDIA's own drivers cannot be used (the current one does not support Kepler; the last Kepler one does not work with CouchLiteOS's display system).
Panel 2560x1440 or 1920x1080	Native mode by default, marked (NATIVE) in Settings > DISPLAY
Broadcom BCM4360 Wi-Fi	Broadcom wl driver
Broadcom Ethernet	Supported with its firmware
Cirrus Logic audio	Supported
Bluetooth	Settings > BLUETOOTH
Apple keyboard	F1-F12 act as function keys (F12 opens the on-screen keyboard); hold Fn for media keys
Brightness	No reports yet. When the backlight can be controlled, the brightness keys and the quick menu's BRIGHTNESS row change it.
Sensors	Shown in SYSTEM DIAGNOSTICS

To see the drivers chosen, run /usr/libexec/couchliteos-hwdetect report in TERMINAL. sudo couchliteos-hardware-report confirms the exact model, GPU and Wi-Fi chip and saves a copy under /var/log/couchliteos/; attach it when you report a bug.

Wi-Fi

Use Settings > NETWORK > JOIN A WI-FI NETWORK. SYSTEM DIAGNOSTICS shows the driver as wl. On an installed system, keep the packages linux-headers-amd64, dkms and broadcom-sta-dkms installed so Wi-Fi keeps working after kernel updates.

Streaming

• Moonlight decodes H.264 in software on the CPU (Kepler has no HEVC decoder, and the open driver's H.264 decoder needs firmware CouchLiteOS cannot ship). Target 1080p60; 1440p60 may drop frames on the Core i5.
• Experimental: Settings > STREAMING > VIDEO DECODER FIRMWARE fetches NVIDIA's decoder firmware from nvidia.com so Moonlight can try hardware H.264 decoding. See Streaming with Moonlight.
• Changes you make in Moonlight's own settings are kept. Setting codec or decoder in /var/lib/couchliteos/config.ini overrides the automatic choice.

Black screen

• Reboot and choose Start CouchLiteOS (No Persistence).
• Never add nomodeset; CouchLiteOS needs the graphics driver.
• See Troubleshooting.

Limits

• The open driver runs the GPU at its boot clocks, so GPU-heavy work is slow. Drawing the launcher on the 2560x1440 panel works.
• Sleep and resume, fan behaviour under load, the headphone jack and the FaceTime camera have no reports yet.