Frequently Asked Questions (FAQ)

Q1: What is CSMWrap?

A: CSMWrap is a UEFI application that allows you to boot legacy BIOS-based operating systems on modern UEFI-only systems. It uses components from SeaBIOS (specifically its Compatibility Support Module and VBIOS) to emulate a traditional PC BIOS environment.

Q2: Why would I need CSMWrap?

A: You might need CSMWrap if:

• You have an older operating system (like DOS, Windows XP, or older Linux versions) that requires a legacy BIOS to boot.
• Your modern computer's firmware is UEFI-only and does not include a built-in CSM.
• You need to run specific legacy software or use hardware with Option ROMs that only work in a BIOS environment.

Q3: Is CSMWrap a replacement for my computer's UEFI firmware?

A: No. CSMWrap is a UEFI application that runs on top of your existing UEFI firmware. It creates a temporary legacy BIOS environment for the purpose of booting a legacy OS. Your system still fundamentally boots via UEFI to launch CSMWrap.

Q4: Do I need to disable Secure Boot?

A: Yes, Secure Boot MUST be disabled to use CSMWrap. CSMWrap is not signed by Microsoft or any hardware vendor, and it performs low-level operations that are incompatible with Secure Boot's security model.

Q5: What is "Above 4G Decoding" / "Resizable BAR" and why do I need to disable it?

A: These UEFI features allow PCI devices (especially graphics cards) to have their memory (BARs) mapped above the 4GB physical address range. Legacy BIOS, Option ROMs (like VBIOS), and 32-bit operating systems generally cannot access memory beyond 4GB. If these features are enabled, the VBIOS used by CSMWrap won't be able to access the video RAM, leading to display issues or boot failures. Disabling them is crucial.

Q6: My motherboard has a "CSM Support" option. Should I enable or disable it?

A: You should try these:

• Try disabling it first. CSMWrap aims to be its own, self-contained CSM. Having the motherboard's native CSM active might lead to conflicts.
• If CSMWrap fails to work with the native CSM disabled, you can try enabling the native CSM. Some motherboards might require their CSM to be enabled for certain very low-level hardware initializations or to allow any legacy Option ROM execution at all, even if CSMWrap then tries to take over. This requires experimentation.

Q7: CSMWrap boots, but my legacy Windows (XP/7) has display issues or a black screen after the loading logo.

A: This is a known issue related to how legacy Windows interacts with the VESA VBIOS (SeaVGABIOS) after the initial boot phase. The best workaround is to try and slipstream/inject native legacy GPU drivers for your graphics card (if they exist for that OS) into your Windows installation media. This allows Windows to use its own driver for modesetting instead of relying solely on INT 10h VBIOS calls.

Q8: Will CSMWrap work on my specific hardware?

A: Maybe. Hardware and UEFI firmware implementations vary greatly. CSMWrap's success depends on its ability to perform tasks like unlocking the legacy BIOS memory region (0xC0000-0xFFFFF). While it includes workarounds for some common chipsets, it's not guaranteed to work on all systems. See the Limitations and Known Issues page.

Q9: Is using CSMWrap risky?

A: Potentially. You are disabling security features like Secure Boot and modifying low-level system memory accessibility settings. While CSMWrap itself is designed to be non-destructive, incorrect UEFI settings or unforeseen interactions could theoretically lead to system instability. Proceed with caution and ensure you know how to reset your UEFI settings to default if needed.

Q10: Where can I get CSMWrap?

A: You can download pre-compiled .efi files from the project's Releases page on GitHub (if available) or Building from Source.

Q11: How is this different from just enabling CSM in my UEFI settings?

A: Many modern motherboards, especially on laptops or newer desktops, no longer offer a built-in CSM option. CSMWrap is for these systems. If your system does have a robust, working native CSM, that is often a simpler solution. CSMWrap offers an alternative or a way to potentially get more control over the legacy environment.