[MinnowBoard] 64-bit vs 32-bit UEFI - What you need to know!

[Hawley, John]

So there's been a bunch of questions about 32-bit OSes on the
MinnowBoard MAX, and a fair amount of confusion on what's going on
there.  I've updated the wiki documentation

http://www.elinux.org/Minnowboard:MaxBios#32-bit_vs._64-bit_UEFI

but figured a quick discussion here would be helpful.

When UEFI was designed they made a conscious and explicit design
decision: Firmware's number of bits should match the OSes number of
bits.  Meaning if firmware is 32-bit, the OS has to be 32-bit.  If
firmware is 64-bit, the OS has to be 64-bit.  There's a variety of
reasons why this decision was made, but it was made.

What this means to MinnowBoard MAX users:  The short version is if you
want to run a 64-bit OS, this entire e-mail is a no-op.  If you want to
run a 32-bit OS, you have to jump through some hoops.

If you *REALLY* want to run a 32-bit OS there's some steps you'll need
to follow, and I've outlined them at 

http://www.elinux.org/Minnowboard:MaxBios#Switching_from_64-bit_to_32-bit

Basically you have to re-flash the firmware with a 32-bit firmware.
There's a line in the instructions that may confuse some folks,
specifically using a FirmwareUpdateX64.efi to flash a 32-bit firmware.
This is because when you go to change the firmware you are running a
64-bit firmware, and therefore need a 64-bit EFI program to actually do
the flashing.

If you want to switch back, you'll do the opposite, use
FirmwareUpdateIA32.efi to flash a 64-bit firmware.

If I've missed something, let me know, I'd rather cover everything we
can in our documentation.

- John 'Warthog9' Hawley