GlouOSAMD X3D cache mode
On dual-CCD Ryzen X3D processors, GlouOS steers games onto the 3D V-Cache cores automatically, the moment a game starts, and gives the high-clock cores back when it ends. No daemon, no settings page, nothing to configure.
Two kinds of cores on one chip
AMD's dual-CCD X3D processors, the Ryzen 9 7900X3D, 7950X3D and 9950X3D, have two different halves. One CCD carries 96 MB of stacked 3D V-Cache at slightly lower clocks; the other has normal cache but higher boost clocks.
| CCD | What it has | Best for |
|---|---|---|
| CCD 0 | 96 MB of stacked 3D V-Cache, slightly lower clocks | Games (cache-hungry) |
| CCD 1 | Higher boost clocks, normal cache | Rendering, compiling, general work |
Games love the giant cache: when a game's threads land on the V-Cache CCD they can gain 10–20% FPS over running on the frequency CCD. On Windows, AMD ships a chipset driver and a "3D V-Cache Performance Optimizer" service to steer games there. On Linux, the kernel exposes the same choice through a sysfs knob:
/sys/bus/platform/drivers/amd_x3d_vcache/<device>/amd_x3d_modeIt accepts cache (prefer the V-Cache CCD) or frequency (prefer the fast CCD). Most distros leave it at the firmware default and never touch it, so games can end up scheduled on the wrong half of the chip.
Switched automatically, per game session
GlouOS flips the mode using the same event-driven hook chain that powers the rest of Game Mode. GameMode's D-Bus signal fires the hooks; there is no polling and no background service.
- Game starts → the
glou-gamemode-starthook writescache, steering the game onto the V-Cache CCD. - Game exits → the
glou-gamemode-endhook writesfrequency, giving desktop work the high-clock cores back.
You get the Windows-style V-Cache optimizer behaviour with zero configuration, and your non-gaming workloads still enjoy the frequency CCD. The hooks run as your user, not root: a small tmpfiles.d rule grants the gamemode group write access to the sysfs knob at boot, and the installer puts every user in that group.
Only on the hardware that needs it
The amd_x3d_vcache sysfs device only exists on dual-CCD X3D parts with a recent kernel (the GlouOS gaming kernel includes the driver). On every other CPU the hooks match nothing and do nothing. There is nothing to configure and nothing to turn off.
Single-CCD X3D chips need no steering
Chips like the 7800X3D and 9800X3D have V-Cache on their only CCD, so every thread already lands on it. On those machines this feature is inert by design, and that is correct behaviour.
Verifying it works
On a dual-CCD X3D machine, you can watch the mode flip from a terminal:
cat /sys/bus/platform/drivers/amd_x3d_vcache/*/amd_x3d_mode # frequency (idle)
gamemoderun sleep 5 & # pretend a game is running
cat /sys/bus/platform/drivers/amd_x3d_vcache/*/amd_x3d_mode # cache (during)How the pieces fit
| File | Role |
|---|---|
/usr/local/bin/glou-gamemode-start | writes cache on game start |
/usr/local/bin/glou-gamemode-end | writes frequency on game exit |
/etc/tmpfiles.d/glouos-gaming.conf | grants the gamemode group write access to the sysfs knob at boot |
| Installer users module | puts every user in the gamemode group |
GlouOS applies the same care to AMD graphics cards: see CoreCtrl GPU tuning for how fan, clock and power controls are unlocked out of the box.