UEFI Boot FAQ
What is UEFI?
Section titled “What is UEFI?”UEFI is a modern startup firmware designed to replace the classic BIOS. The old BIOS has limitations in both software and hardware. UEFI is designed to be extensible and more capable.
For technical information, see Unified Extensible Firmware Interface on Wikipedia.
Why do I need BIOS or UEFI?
Section titled “Why do I need BIOS or UEFI?”Before your computer or tablet can connect to its built-in storage device and boot an operating system, it needs to initialize its internal devices and make the system ready for boot. This is done with internal firmware like the legacy BIOS or the more modern UEFI.
Why do I need to build UEFI-specific boot images?
Section titled “Why do I need to build UEFI-specific boot images?”The boot files are specific to the firmware and the processor architecture. When you create a boot image, you select Create Boot Image for 32-bit systems, which is used for legacy BIOS clients and 32-bit UEFI clients, or Create Boot Image for 64-bit UEFI systems, which is used for 64-bit UEFI clients. See Create a boot image.
How can I tell if my device is UEFI-based?
Section titled “How can I tell if my device is UEFI-based?”Most newer computers and devices support UEFI boot. Check the official specifications of your device to see what level of UEFI boot your device supports.
How do I enable UEFI boot from the network on my device?
Section titled “How do I enable UEFI boot from the network on my device?”Vendors present the UEFI options in their firmware in different ways. Refer to the official documentation, and note the firmware version of the device, to find the setting that enables UEFI network boot.
I have enabled UEFI as a boot method, but I can’t boot from the network
Section titled “I have enabled UEFI as a boot method, but I can’t boot from the network”Check if the UEFI setting explicitly mentions network boot. Some early devices support UEFI boot from internal disks or USB, but not from the network interface card.
My device supports network boot over UEFI, but it still won’t boot
Section titled “My device supports network boot over UEFI, but it still won’t boot”UEFI network boot works with Secure Boot enabled, because the UEFI boot files come from the Windows ADK and are signed by Microsoft. If the device reports “Secure Boot Violation, Invalid Signature Detected”, or returns to the firmware menu right after it gets an IP address, see OS Deployment and PXE Boot Issues. Some devices also require the Microsoft UEFI CA key to be enabled in the Secure Boot configuration.
Which network adapters are supported for PXE/UEFI boot?
Section titled “Which network adapters are supported for PXE/UEFI boot?”There is no class driver for USB network adapters, and individual chips have notable functional differences. Support for USB network adapters is therefore left to the manufacturer of the motherboard, who must build support for the individual chips into the firmware.
The BIOS/UEFI on the motherboard must natively support the chip used in the USB network adapter. The answer always depends on the motherboard, and requires research into both the chipset of the USB network adapter and whether the BIOS/UEFI of the motherboard supports this chip.
Most legacy systems can’t PXE boot from a USB network adapter. On more modern systems, this varies from model to model.
Newer USB 3.0 network adapters are less likely to work than USB 2.0 adapters. USB 2.0 adapters are based on chips that have been around longer, which has given motherboard manufacturers time to add support for them.
Why does the transfer of boot.wim fail or run very slowly?
Section titled “Why does the transfer of boot.wim fail or run very slowly?”The time it takes to download the boot image depends on your network card and the size of the boot image.