Writing sel4.iso on a CD/DVD vs. on an USB key

[Paul Dufresne]

At first I had burned sel4.iso on a CD, but no computer was able to
boot from it.

Then rereading the instructions, I saw it was asked to DD it to an USB
key, which I did,
and was getting much better results: a grub menu that disappears so
fast that it only goes
to loading the first module, then the boot module.

I kind of know that sectors on CD are supposed to be 2k in size, and
0.5k on most other
mediums, like USB key normally... I think.

I know Linux distribution can often be put on both DVD and USB keys
without thinking much.

Why (is?) Genode would be different?