I don't have a 790 or 980, but do have 780's, 990's and 9010's (along with others, but it'll take a while to test them all). So far, I've tested it successfully on a 780 (BIOS Rev. A03.)
When you hit F12 for the boot menu, select "Onboard or USB CD-ROM Drive". It will likely give the "Selected boot device not available - Strike F1 to retry boot, F2 for setup utility, Press F5 to run onboard diagnostics" error. If you press F1, it will then boot to the ISOStick. The first time you boot to it, it will bring up the ISOSel boot menu. Select the ISO you want to boot. It will then reboot. Press F12 for boot menu again, select the "Onboard or USB CD-ROM Drive" again. It will throw that same error, press F1 and it should then begin booting into the ISO you had selected.
I'll see about testing on additional systems. Currently, my issue is that it seems to be quite slow (Like, optical drive slow if not slower). Not sure if it's something with the 780 I'm testing on or what. I'll test on another system and if it's still slow, I'll try re-formatting the drive with Rufus. I originally formatted it with Fat32format.exe.
Ok, currently testing on a 755. Same deal. It has the same issue of having to hit F1 in order to boot from the stick and it's slow. I'm going to try a re-format to see if that clears up the speed issue.
Edited by TWBalls, 04 October 2013 - 11:13 PM.