AMD RadeonSI Driver Advances: Medium Precision ("mediump") Support Nears Completion

 

AMD RadeonSI driver progresses toward 16-bit medium precision (mediump) support with critical Mesa 25.3 fixes. Learn how these GPU optimizations impact gaming, AI workloads, and high-performance computing. Expert analysis on Marek Olšák’s latest contributions.

Key Developments in RadeonSI’s Mediump Support

Prominent AMD Mesa developer Marek Olšák has merged 13 critical patches into Mesa 25.3, bringing the open-source RadeonSI Gallium3D driver closer to full 16-bit medium precision ("mediump") support. 

This optimization targets improved shader efficiency, benefiting gaming, machine learning inference, and real-time rendering workloads.

Technical Breakdown: Fixes & Workarounds

• 16-bit I/O Precision: Patches address mediump handling in shader pipelines, including fixes for:

  • Transform Feedback (XFB) data lowering to 16-bit.

  • Edge cases in linked shaders (non-XFB scenarios).

• RADV Workaround: A temporary fix for AMD’s Vulkan driver (nir_opt_vectorize_io) was included.

• Shader Pipeline Flexibility: New shader_info fields allow selective 32-bit fallback for unstable cases.

*"These fixes allow drivers to support mediump IO for non-XFB linked shaders while keeping 32-bit precision where needed."*
— Marek Olšák, AMD Mesa Developer

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Why This Matters for High-Performance GPUs

1. Gaming & Real-Time Rendering

Mediump support reduces memory bandwidth usage, potentially boosting FPS in titles leveraging shader-heavy effects (e.g., ray-traced shadows).

2. AI/ML Workloads

16-bit precision is critical for lightweight AI inference, aligning with AMD’s push for Radeon GPUs in edge computing.

3. Competitive Benchmarking

With NVIDIA’s DLSS and Intel’s XeSS relying on similar optimizations, this update keeps RadeonSI competitive in the premium GPU market.

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Roadmap & Remaining Challenges

While mediump support isn’t finalized, Olšák confirmed progress:

• Pending Fixes: gl_nir_lower_packed_varyings requires adjustments for XFB compatibility.

• Target Release: Mesa 25.2 (next quarter) or later.

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Frequently Asked Questions (FAQ)

Q: How does mediump improve GPU performance?

A: By reducing precision from 32-bit to 16-bit, shaders execute faster with lower memory overhead.

Q: Will this benefit professional workloads like Blender or DaVinci Resolve?

A: Indirectly—optimized shaders improve overall driver stability, but app-specific optimizations are still needed.

Q: Is this relevant for budget GPUs like the RX 7600?

A: Yes! Efficiency gains are especially valuable for mid-range hardware.