Disable RAM RGB (G.SKILL Trident Z RGB, DDR4)

A quick note-to-future-me for turning off RAM LEDs from Linux using the crgb.cc approach.

---

What this program does (summary of the script)

• Enumerates Linux I²C adapters under /sys/bus/i2c/devices/, resolves each adapter’s PCI vendor/device IDs, and opens the matching /dev/i2c-*.
• Filters for AMD FCH SMBus adapters (vendor 0x1022, device 0x790B).
• Probes I²C address 0x77 (typical ENE/Aura RAM LED controller on DDR4 G.SKILL Trident Z RGB).
• If the device at 0x77 ACKs, it performs ENE controller writes to switch LEDs off and apply the change.
• Uses Linux SMBus ioctls for safe access (no raw bit-banging).

Result: RAM LEDs turn off at boot (you’ll re-run it via cron so it always applies).

---

My local filenames & layout

• Source file: disable_ram_rgb.cc
• Executable: disable_ram_rgb

These replace the original author’s filenames; functionality stays the same.

---

Dependencies (my install)

Debian/Ubuntu:

sudo apt update
sudo apt install -y g++ i2c-tools

---

Build & run

# build
sudo g++ disable_ram_rgb.cc -o /root/disable_ram_rgb

# run once now (needs root to open /dev/i2c-*)
sudo /root/disable_ram_rgb

If it runs without error and the LEDs go dark, you’re set.

---

Auto-run at boot (cron)

sudo crontab -e
# add:
@reboot /root/disable_ram_rgb

Cron runs it at every boot so LEDs stay off without manual steps.

---

Quick verification / sanity

List I²C buses:

i2cdetect -l

On systems like this one you’ll typically see an AMD PIIX4 SMBus (e.g. i2c-13). You can (read-only) probe a controller address if you need to troubleshoot:

sudo i2cdetect -y -r 13 0x70 0x77
# A hit at 0x77 means the ENE controller is visible on that bus.

---

Notes & gotchas

• The program is deliberately conservative: it only acts on AMD FCH SMBus and address 0x77. If you move platforms (e.g., Intel) or your RAM maps the controller elsewhere, it’ll safely do nothing until you adapt the filter/addr.
• Running as root is required to access /dev/i2c-*.
• Some boards gate SMBus via ACPI; if you ever can’t see 0x77, that’s likely why (not a program bug).
• This approach does not write a persistent LED profile into the module; using cron @reboot is the right pattern.

---

Credits

• Based on aditya-r-m’s crgb.cc script (GitHub Gist).
• Hardware: G.SKILL TridentZ RGB Series 64GB (4×16GB) DDR4-3600, F4-3600C16Q-64GTZRC.
• Chipset path: AMD FCH SMBus [1022:790B] → I²C 0x77 (ENE/Aura).

---

TL;DR

1. Save the script as disable_ram_rgb.cc.
2. sudo apt install g++ i2c-tools
3. sudo g++ disable_ram_rgb.cc -o /root/disable_ram_rgb
4. sudo /root/disable_ram_rgb (watch LEDs turn off)
5. Add @reboot /root/disable_ram_rgb to root crontab.