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I'm having an issue with my pc. I want to boot from USB flash drive. I enter BIOS and select the first boot device and select my USB flash drive. The changes do not reflect on the screen. If I just press F12 after post, and select my USB flash drive, it doesn't boot.

I disconnected two of three new HDD I've added to my array pool. I can now select and apply my boot order changes and boots properly. I have a total of 10 hdd (2tb each) but can only use 8 hdd to boot correctly. Is this a PSU issue? I'm currently running a 750w PC Power and Cooling PSU. No discrete gpu, only acting as a NAS.

I've tried clearing CMOS but no luck either. Should I start with replacing the PSU or mobo first?

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Are you asking about saving in the BIOS, ensure a partition is bootable or possible PSU issues? Focus on one problem and fix that; anything other than working systematically is just guessing. – Richard Nov 22 '12 at 9:26

This is likely to be a bug in the BIOS of your motherboard. Developers of the BIOS probably did not prepare for more than 8 devices to choose from at boot.

I would advise to check if there is a new BIOS version available for your motherboard. If there is no update, your most easy option is to replace the motherboard, preferably for one that you can verify will accept more than eight boot devices.

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