Environment Variables Guide¶

This guide covers all environment variables for BC-250 graphics configuration, performance tuning, and debugging.

Critical Environment Variables¶

RADV_DEBUG=nocompute¶

Status: Required for most games (Mesa < 25.1)

The most important environment variable for BC-250 gaming. Forces games to use the graphics queue instead of the broken compute queue.

What it does: The BC-250's compute queue has hardware issues that cause graphical artifacts and rendering problems. This variable forces all workloads through the graphics queue instead.

When to use:

Always set for gaming on Mesa versions before 25.1
May not be needed on Mesa 25.1+ due to MR #33116 which disables the compute-only queue by default

How to set:

# Steam launch options
RADV_DEBUG=nocompute %command%

# System-wide (add to /etc/environment)
RADV_DEBUG=nocompute

# Per-application
RADV_DEBUG=nocompute ./game

RADV_DEBUG=nohiz¶

Purpose: Fixes additional graphical artifacts

Some games experience rendering issues even with nocompute. This variable disables hierarchical Z-buffer optimization.

When to use:

If you see visual artifacts or glitches in games
Can be combined with other RADV_DEBUG options

How to set:

# Combine multiple RADV_DEBUG flags with commas
RADV_DEBUG=nocompute,nohiz %command%

RADV (Vulkan Driver) Variables¶

VK_ICD_FILENAMES¶

Purpose: Explicitly specify Vulkan driver location

Required for hardware acceleration in some applications, particularly Steam Big Picture mode.

Usage:

export VK_ICD_FILENAMES=/usr/share/vulkan/icd.d/radeon_icd.x86_64.json:/usr/share/vulkan/icd.d/radeon_icd.i686.json

When needed:

Steam Big Picture hardware acceleration
Applications not finding Vulkan driver automatically
Flatpak applications (different path)

radv_enable_unified_heap_on_apu¶

Purpose: Workaround for memory allocation issues

Enables unified memory heap on APU systems. Helps with out-of-memory errors on some games.

Configuration:

Add to /etc/drirc:

<driconf>
    <device>
        <application name="Default">
            <option name="radv_enable_unified_heap_on_apu" value="true" />
        </application>
    </device>
</driconf>

When needed:

Games crashing with memory errors
Applications not utilizing full VRAM
Mesa versions before full BC-250 memory support

AMD GPU Variables¶

AMD_LOG_LEVEL¶

Purpose: Debugging AMD driver issues

Controls verbosity of AMD GPU driver logging.

Values:

0 - Errors only
1 - Warnings
2 - Info
3 - Verbose
4 - Debug (very verbose)

Usage:

AMD_LOG_LEVEL=4 ./application

When to use:

Troubleshooting driver issues
Debugging ROCm/compute problems
Investigating crashes or hangs

HSA_OVERRIDE_GFX_VERSION¶

Purpose: Override GPU architecture detection

Forces applications to treat the BC-250 (gfx1013) as a different architecture.

Common values:

10.1.0 - Pretend to be gfx1010 (RDNA 1.0)
10.3.0 - Pretend to be gfx1030 (RDNA 2.0)

Usage:

HSA_OVERRIDE_GFX_VERSION=10.1.0 ./rocm-application

When to use:

ROCm applications that don't support gfx1013
Getting limited support in compute workloads
LLM inference with llama.cpp (limited success)

Warning: This is a workaround and may cause instability or incorrect results.

LLM/Compute Variables¶

GGML_VK_FORCE_MAX_ALLOCATION_SIZE¶

Purpose: Limit Vulkan memory allocation size for llama.cpp

Prevents out-of-memory errors by limiting single allocation size.

Value:

GGML_VK_FORCE_MAX_ALLOCATION_SIZE=2000000000  # 2GB in bytes

When to use:

Running llama.cpp with Vulkan backend
Out-of-memory errors with large models
Memory fragmentation issues

Performance:

Enables 4-bit quantized 8B models at ~60 tokens/sec
Vulkan sees only ~10GB of 12GB VRAM split (limitation)

TTM Module Configuration¶

Purpose: Control GPU shared memory management

The TTM (Translation Table Manager) module manages shared memory between CPU and GPU.

Configuration:

Create /etc/modprobe.d/ttm-mem-limit.conf:

options ttm pages_limit=3959290 page_pool_size=3959290

What it does:

Sets available memory pages for GPU (value in 4KB pages)
Default may only allow 8GB even with 12GB VRAM split
Allows full RAM to be available for VRAM if necessary

Calculate pages_limit:

# For 15GB available to GPU (3959290 pages × 4KB)
# (Total RAM - 1GB) / 4096 bytes per page

Performance Variables¶

mitigations=off¶

Type: Kernel boot parameter (not environment variable)

Disables CPU security mitigations for better processor performance.

How to set:

Edit /etc/default/grub:

GRUB_CMDLINE_LINUX_DEFAULT="... mitigations=off"

Then update GRUB:

# Fedora/RHEL
sudo grub2-mkconfig -o /boot/grub2/grub.cfg

# Debian/Ubuntu
sudo update-grub

Performance gain:

5-10% CPU performance improvement
Particularly helps with emulation and CPU-bound games

Security trade-off:

Disables Spectre, Meltdown, and other vulnerability mitigations
Only use on trusted/isolated systems

Flatpak Variables¶

FLATPAK_GL_DRIVERS¶

Purpose: Force Flatpak to use specific Mesa drivers

Enables mesa-git drivers in Flatpak applications.

Setup:

sudo mkdir -p /etc/systemd/system/service.d
sudo bash -c 'echo -e "[Service]\nEnvironment=FLATPAK_GL_DRIVERS=mesa-git" > /etc/systemd/system/service.d/99-flatpak-mesa-git.conf'

flatpak remote-add --if-not-exists flathub-beta https://flathub.org/beta-repo/flathub-beta.flatpakrepo
flatpak install --system flathub-beta org.freedesktop.Platform.GL.mesa-git//24.08
flatpak install --system flathub-beta org.freedesktop.Platform.GL32.mesa-git//24.08

ROCm Variables (Limited Support)¶

GGML_HIP_UMA¶

Purpose: Enable Unified Memory Architecture for HIP

Used when compiling llama.cpp with ROCm support.

Usage:

HIPCXX="$(hipconfig -l)/clang" HIP_PATH="$(hipconfig -R)" \
cmake -S . -B build \
  -DLLAMA_CURL=ON \
  -DGGML_HIP=ON \
  -DAMDGPU_TARGETS=gfx1013 \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_HIP_COMPILER_ROCM_ROOT=/usr \
  -DGGML_HIP_UMA=ON

Current status:

ROCm support is very limited on BC-250
rocBLAS missing gfx1013 binaries (TensileLibrary_lazy_gfx1013.dat)
Workarounds produce gibberish output
Vulkan backend recommended instead

Setting Variables¶

Per-Game (Steam)¶

Right-click game > Properties > Launch Options:

RADV_DEBUG=nocompute %command%
RADV_DEBUG=nocompute,nohiz DXVK_HUD=fps %command%

System-Wide (All Applications)¶

Edit /etc/environment:

RADV_DEBUG=nocompute
VK_ICD_FILENAMES=/usr/share/vulkan/icd.d/radeon_icd.x86_64.json:/usr/share/vulkan/icd.d/radeon_icd.i686.json

Per-Session (Terminal)¶

export RADV_DEBUG=nocompute
export AMD_LOG_LEVEL=2
./your-application

systemd Service Files¶

For services like game servers:

[Service]
Environment="RADV_DEBUG=nocompute"
Environment="VK_ICD_FILENAMES=/usr/share/vulkan/icd.d/radeon_icd.x86_64.json"

Proton/Wine Variables¶

DXVK_HUD¶

Purpose: Display DXVK performance overlay

DXVK_HUD=fps,gpu,cpu %command%

PROTON_LOG¶

Purpose: Enable Proton debug logging

PROTON_LOG=1 %command%

PROTON_USE_WINED3D¶

Purpose: Use OpenGL instead of Vulkan

Fallback if Vulkan has issues:

PROTON_USE_WINED3D=1 %command%

Debugging Variables¶

RADV_PERFTEST¶

Purpose: Enable experimental RADV features

RADV_PERFTEST=nggc,sam  # Example: NGG culling, Smart Access Memory

Warning: Experimental features may cause instability.

MESA_DEBUG¶

Purpose: Mesa driver debugging

MESA_DEBUG=1  # Enable debug output

OpenCL Variables¶

RUSTICL_ENABLE¶

Purpose: Enable Rusticl OpenCL implementation

RUSTICL_ENABLE=radeonsi

Note: OpenCL support on BC-250 is limited. The GPU may not be recognized as a GPU device.

Complete Gaming Setup Example¶

Recommended launch options for Steam games:

RADV_DEBUG=nocompute mangohud %command%

With additional debugging:

RADV_DEBUG=nocompute,nohiz DXVK_HUD=fps,gpu MANGOHUD=1 %command%

Environment Variable Precedence¶

Variables are applied in this order (later overrides earlier):

System-wide /etc/environment
User profile ~/.profile or ~/.bashrc
systemd service files
Steam launch options
Direct command line VARIABLE=value ./app

Verification¶

Check if variables are set:

# Show all environment variables
env | grep -i radv
env | grep -i amd

# Test Vulkan
vulkaninfo | grep -i "device name"

# Check if driver found
glxinfo | grep -i "opengl renderer"

Mesa 25.1+ Changes¶

With Mesa 25.1 and later:

RADV_DEBUG=nocompute may no longer be needed (compute queue disabled by default)
Test without the variable first
If issues persist, re-enable it
Monitor Mesa MR #33116 status

Troubleshooting¶

Games not using GPU¶

Check:

VK_ICD_FILENAMES=/usr/share/vulkan/icd.d/radeon_icd.x86_64.json vulkaninfo

Still getting artifacts¶

Try:

RADV_DEBUG=nocompute,nohiz %command%

Memory errors¶

Add to /etc/drirc:

<option name="radv_enable_unified_heap_on_apu" value="true" />

ROCm not working¶

ROCm support is experimental and very limited. Use Vulkan instead.

/etc/environment - System-wide variables
/etc/drirc - Mesa driver configuration
/etc/modprobe.d/ - Kernel module options
~/.bashrc - User environment variables
~/.config/MangoHud/MangoHud.conf - MangoHud settings

Summary Table¶

Variable	Purpose	Required	Value
`RADV_DEBUG=nocompute`	Fix compute queue	Yes (Mesa < 25.1)	`nocompute`
`RADV_DEBUG=nohiz`	Fix artifacts	Sometimes	`nohiz`
`VK_ICD_FILENAMES`	Vulkan driver path	For Steam Big Picture	See above
`AMD_LOG_LEVEL`	Debug logging	Debug only	`0-4`
`HSA_OVERRIDE_GFX_VERSION`	ROCm compat	ROCm only	`10.1.0`
`GGML_VK_FORCE_MAX_ALLOCATION_SIZE`	llama.cpp memory	LLM inference	`2000000000`
`mitigations=off`	CPU performance	Optional	kernel param

Best Practices¶

Start with minimal variables (RADV_DEBUG=nocompute only)
Add variables only when needed for specific issues
Test changes one variable at a time
Document working configurations per game
Remove variables when no longer needed (e.g., Mesa 25.1+ may not need nocompute)
Use per-game settings in Steam rather than system-wide when possible

Environment Variables Guide¶

Critical Environment Variables¶

RADV_DEBUG=nocompute¶

RADV_DEBUG=nohiz¶

RADV (Vulkan Driver) Variables¶

VK_ICD_FILENAMES¶

radv_enable_unified_heap_on_apu¶

AMD GPU Variables¶

AMD_LOG_LEVEL¶

HSA_OVERRIDE_GFX_VERSION¶

LLM/Compute Variables¶

GGML_VK_FORCE_MAX_ALLOCATION_SIZE¶

TTM Module Configuration¶

Performance Variables¶

mitigations=off¶

Flatpak Variables¶

FLATPAK_GL_DRIVERS¶

ROCm Variables (Limited Support)¶

GGML_HIP_UMA¶

Setting Variables¶

Per-Game (Steam)¶

System-Wide (All Applications)¶

Per-Session (Terminal)¶

systemd Service Files¶

Proton/Wine Variables¶

DXVK_HUD¶

PROTON_LOG¶

PROTON_USE_WINED3D¶

Debugging Variables¶

RADV_PERFTEST¶

MESA_DEBUG¶

OpenCL Variables¶

RUSTICL_ENABLE¶

Complete Gaming Setup Example¶

Environment Variable Precedence¶

Verification¶

Mesa 25.1+ Changes¶

Troubleshooting¶

Games not using GPU¶

Still getting artifacts¶

Memory errors¶

ROCm not working¶

Related Configuration Files¶

Summary Table¶

Best Practices¶