I managed to get around it using a rEFInd CD with the Arch install ISO written on to my USB stick. The archiso boot menu was detected by rEFInd and worked right away, with gummiboot appearing.
]]>Press ESC in X seconds to skip startup.nsh or any other key to continue.
then
2.0 Shell >
Whether I skip it startup.nsh or not, I get the same result.
I've cruised all the EFI documentation, and I was expecting to see gummiboot or at least something that would start the Arch ISO.
I thought maybe it was motherboard, but I get the same thing through Virtualbox and using both the ISO as a CD, or writing it to a USB disk.
Any help appreciated.
]]>