Understanding Boot Override Issues on Modern Motherboards: A Case Study
Building a new PC is an exciting endeavor, but it can also present unexpected technical challenges. Recently, I encountered an intriguing boot-related anomaly that highlights some of the complexities associated with UEFI firmware and USB booting procedures. Here, I’ll share my experience and insights to help others troubleshoot similar issues.
The Scenario
After assembling a high-performance rig featuring a CPU, motherboard, RAM, and other components, I installed Windows 11 and conducted preliminary tests using tools such as Cinebench and MemTest86. During this process, I observed an unusual behavior concerning how certain bootable USB drives are recognized by my system’s BIOS.
The core issue involves the discrepancy between booting from USB drives via boot order settings versus boot override options within the BIOS.
What Works
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Boot from USB via Boot Order: Setting the USB drive as the primary boot device in BIOS, saving, and rebooting allows the system to successfully load the desired environment—be it MemTest86 or other bootable tools.
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Boot from USB via Boot Override: Selecting the USB drive directly in the “Boot Override” menu (from within BIOS) also results in successful boots for certain images like Windows 11 installer and Ubuntu 24.04.
What Doesn’t Work
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Boot from USB via Boot Override: Attempting to select the same bootable drives, such as MemTest86 or Ubuntu 22.04, directly in the Boot Override menu causes the system to display a blank screen after initiation. The monitor light indicates activity, but no display output occurs.
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Boot from USB using the same images consistently through saved boot order suggests there’s an inconsistency between the two boot methods.
Key Observations
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The discrepancy appears specific to USB drives with certain bootable images (MemTest and Ubuntu 22.04). These images boot perfectly when configured in the boot order but fail to load via Boot Override.
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Conversely, bootable images like Windows 11 installer and Ubuntu 24.04 bypass this issue, working flawlessly in both methods.
Potential Causes and Considerations
Initially, I suspected issues related to UEFI Secure Boot, GPT partitioning, or EFI boot modes. However, since these images boot correctly via the saved boot order, these factors seem less likely to be the root cause.
Some possibilities include:
- Bootloader Formatting and Compatibility: Variances in how different bootable
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