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We had a server running Big-IP and we through out the server hardware and (many years latter) I'm trying to wipe the hard disk. I was trying to boot in to a System Rescue CD so I can run Darik's Boot And Nuke from it and it wouldn't boot from the CD. The first time I turned on the machine there was an error saying no keyboard detected. I unplugged the USB keyboard from the front and plugged it into the back and restarted the machine. This error didn't come back but an prompt saying "Boot: " came up where I could type stuff but couldn't get any commands to run. I tested the keyboard on another computer and it worked. Just to see what happened, I tried a PS/2 keyboard to see what would happen and low and behold I was able to get into the boot menu, boot from the CD and launch DBAN.

Someone was telling me this has happened before with Ghost images and other times we've tried booting from disks. He said the BIOS interface isn't always compatible with the USB ports. Is this true and is there any way of telling in advanced if a machine isn't compatible with a USB keyboard even though the keyboard appears to work?

Note: I was unable to get into the boot menu with the USB keyboard but I was able to type stuff into t "Boot: " and reboot the computer with ctrl+alt+delete so at least the keyboard was detected. But with the PS/2 I was able to press F12 and get to the boot menu. Does this mean USB devices aren't registered until after the system has finished booting?

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Do you have legacy usb support enabled in the bios? – spuder Aug 8 '13 at 18:27

It most likely has to do with the Legacy USB Support setting in your BIOS. Hopefully it's exposed to you in the UI and you can change it.

Legacy USB Support is often required for USB KB's to work in the BIOS (and in legacy OS's like DOS) -- at least on older motherboards.

For more information perhaps check out this other SU question:

What does "Legacy USB Mouse" support in a BIOS mean?

So, if the USB keyboard isn't detected by the BIOS, then (depending on other BIOS settings) the POST will often stop and tell you there's no keyboard, and wait for you to correct it -- causing the Boot to not happen.

enter image description here

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