Steam Deck Mode on Cachy OS – Full GameScope Launcher for NVIDIA & AMD (No Desktop Overhead)

In this video, I release a pure GameScope launcher for CachyOS (KDE Plasma edition) — built so I can benchmark CachyOS properly against Omarchy and my hybrid “FrankenOS” build using the exact same gaming environment.

website : https://www.no-signal.uk

This is essentially the same GameScope launcher I built for Omarchy — but adapted specifically for CachyOS running KDE Plasma, so performance comparisons are fair and consistent.

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🔹 Why This Exists

As many of you know, I’ve been experimenting with a hybrid system:
• Omarchy front end
• CachyOS repositories underneath
• Trying to squeeze a few extra FPS out of the system

To test that properly, I needed:
• A clean base CachyOS install
• The exact same GameScope workflow
• Identical Proton, Vulkan and overlay setup
• Same benchmark conditions

So this launcher is basically a by-product of that testing.

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🔹 Important Installation Notes

This version is built specifically for:
• KDE Plasma
• GRUB bootloader
• NVIDIA or AMD dGPUs

You must:
• Select GRUB during CachyOS install
• Install KDE Plasma
• Reboot after the script modifies GRUB (modset requirement)

It will not work correctly if you use systemd-boot or rEFInd — this version is GRUB-only.

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🔹 What It Does

The script installs:
• Steam
• GameScope
• Vulkan
• Proton GE
• MangoHud
• Required input group permissions
• GRUB kernel parameters

Once installed:
• Super + Alt + S → Launch full GameScope session
• KDE shuts down
• Steam launches in Deck-style mode
• Super + Alt + R → Exit cleanly back to desktop

No compositor conflicts.
No nested sessions.
No Wayland mouse issues.

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🔹 NVIDIA Limitation

GameScope UI is locked to:

2560×1440

This is an NVIDIA limitation.

You can still run games at 4K inside the stream, but the interface itself must stay at 1440p or below or it will corrupt.

HDR should also be disabled.

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🔹 Benchmark Results (Real Numbers)

Benchmarks were run across:
• Vanilla Omarchy
• CachyOS Deck mode
• Hybrid Omarchy + Cachy
• Base CachyOS + this GameScope launcher

Results:

Cyberpunk → All within 1 FPS
Homeworld 3 → Base Cachy slightly ahead
Doom → Hybrid slightly ahead
Overall → Differences are tiny

On high-end GPUs, you’re chasing 1–4 FPS.
On lower-end hardware, gains are slightly more noticeable.

Vanilla Arch is already extremely fast.

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🔹 GPU Support
• ✅ AMD – Supported
• ✅ NVIDIA – Supported (1440p UI limit)
• ❌ Intel – Not supported (requires Mesa Git, destabilises system)
• ⚠️ APUs – Untested
• ⚠️ Laptops – Limited testing

If you install without the dGPU active, detection can fail.

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🔹 Why You’d Use This

If you already run CachyOS and want:
• Steam Deck–style gaming
• Clean GameScope isolation
• No compositor overhead
• Simple keybind launch
• Automatic Steam library detection

This gives you that — without reinstalling into a Deck-mode OS.

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💬 Final Thoughts

Performance differences are tiny.

This isn’t about magic FPS boosts.
It’s about having a consistent, clean GameScope workflow across:
• Omarchy
• CachyOS
• Hybrid builds

So I can benchmark properly — and so you can too.

The hybrid ISO project continues…