[MinnowBoard] 64-bit vs 32-bit UEFI - What you need to know!
Darren Hart
dvhart at linux.intel.com
Tue Sep 9 17:13:16 UTC 2014
On 9/9/14, 10:03, "Hawley, John" <john.hawley at intel.com> wrote:
>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.
The only thing I would point out is that instead of OS, you really mean
kernel. For example, it is perfectly valid to run a 64b firmware, 64b
Linux kernel, and a 32b Linux userspace. It's the firmware_efi <->
kernel_efi interface that has to match here.
--
Darren Hart Open Source Technology Center
darren.hart at intel.com Intel Corporation
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