I am trying to run Ubuntu 12.04.05 via USB. It shows the option to run via USB on one of my computers, but not the other 2. How can I get it to display on these other computers?
1) On my oldest computer (32 bit Intel), it shows the following screen which is fine:
2) On my 2 newer computers (which are both barebones / nuc computers, one is 64 bit Intel, another is AMD 32 bit) I get the following GRUB screen which doesn't offer the option to run from USB: