Welcome to the CSMWrap Wiki!

CSMWrap is a UEFI application designed to enable legacy BIOS booting on modern UEFI-only systems. It achieves this by leveraging the Compatibility Support Module (CSM) and VESA VBIOS components from the SeaBIOS project, effectively emulating a traditional PC BIOS environment.

This project aims to bridge the gap for users and developers who need to run operating systems or software that strictly require a legacy BIOS, on hardware that no longer provides one natively.

Features

• Legacy BIOS Emulation: Provides INT 10h (video), INT 13h (disk), and other essential BIOS interrupts.
• SeaBIOS CSM Integration: Utilizes a specially compiled SeaBIOS CSM (Csm16.bin) for core compatibility logic.
• SeaVGABIOS for Video: Includes SeaVGABIOS for VESA VBE support, initialized using information from EFI GOP.
• E820 Memory Mapping: Constructs an E820 memory map compatible with legacy OSes, derived from the UEFI memory map.
• ACPI & SMBIOS Passthrough: Attempts to provide necessary ACPI tables (RSDP) and SMBIOS information to the legacy environment.
• Coreboot Table Generation: Can generate a Coreboot table for payloads that might expect it.
• Cross-Architecture Support: Builds for both IA32 (x86) and x86_64 UEFI systems.
• Open Source: Based on Nyu-EFI, uACPI, and other open components.

Current Status

CSMWrap has been successfully tested to:

• Boot FreeDOS.
• Boot Windows XP and Windows 7 in QEMU (q35 and PIIX4 machine types).
• Run on some real hardware (compatibility varies).

Navigation

• Building from Source
• Usage Guide
• Partitioning and Boot Scenarios
• Platforms
• Compatibility
• How CSMWrap Works
• Limitations and Known Issues
• Troubleshooting
• Contributing
• FAQ

Quick Start

1. Get CSMWrap:
   • Download a pre-compiled .efi file from the Releases page.
   • Or, Building from Source.
2. Prepare your UEFI System:
   • Disable Secure Boot.
   • Disable Above 4G Decoding (and/or Resizable BAR/SAM). This is crucial for legacy VBIOS compatibility.
   • If your firmware has a "CSM Support" option, try disabling it first. If CSMWrap fails, you might need to enable it, but this can conflict.
3. Boot:
   • Copy the appropriate csmwrapx64.efi or csmwrapia32.efi to your EFI System Partition (e.g., EFI/BOOT/BOOTX64.EFI or EFI/BOOT/BOOTIA32.EFI).
   • Boot from the EFI file.

For more detailed instructions, please refer to the Usage Guide and Partitioning and Boot Scenarios.

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This project is a work-in-progress. While it aims to provide robust legacy support, hardware and firmware variations can impact its functionality.