add amdvbflash tool and README with BIOS extraction guide

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -0,0 +1,56 @@
+# GPU BIOS Collection
+
+A collection of GPU BIOS ROM files and tools for extracting/flashing them.
+
+## Extracting GPU BIOS on Linux (AMD)
+
+### Prerequisites
+
+- Root/sudo access
+- `amdvbflash` (included in `bin/`)
+
+### Steps
+
+1. **Identify your GPU adapter index:**
+
+   ```bash
+   sudo ./bin/amdvbflash -i
+   ```
+
+   This lists all detected AMD GPUs with their adapter numbers (e.g., `0`, `1`, etc.).
+
+2. **Extract (save) the BIOS to a ROM file:**
+
+   ```bash
+   sudo ./bin/amdvbflash -s 0 output.rom
+   ```
+
+   Replace `0` with your adapter number from step 1, and `output.rom` with your desired filename.
+
+3. **Verify the saved file:**
+
+   ```bash
+   ls -la output.rom
+   ```
+
+   A valid ROM file is typically 256KB-512KB for most AMD GPUs.
+
+### Notes
+
+- `amdvbflash` must be run as root (`sudo`).
+- The tool supports AMD Radeon GPUs. For NVIDIA GPUs, use `nvflash` instead.
+- Always save a backup of your stock BIOS before flashing any modifications.
+- The included `amdvbflash` binary is v4.71 for Linux x86_64.
+
+### Quick Reference
+
+| Command | Description |
+|---|---|
+| `sudo ./bin/amdvbflash -i` | List detected AMD GPUs |
+| `sudo ./bin/amdvbflash -s <adapter> <file.rom>` | Save BIOS to file |
+| `sudo ./bin/amdvbflash -p <adapter> <file.rom>` | Flash BIOS from file |
+
+## Files
+
+- `bin/amdvbflash` - AMD VBIOS flash tool v4.71 (Linux), downloaded from [TechPowerUp](https://www.techpowerup.com/download/ati-atiflash/)
+- `amd-rx5600xt.rom` - AMD RX 5600 XT BIOS dump