Steve's blog

You might have seen some of the posts I've written in the last few months about adding support in Debian for so-called Mixed-EFI systems like the Intel Bay Trail: a 64-bit processor shipped with a 32-bit EFI implementation.

I've finally seen a public justification from Intel evangelist Brian Richardson as to why these systems are crippled^Wconfigured this way, and it's nice to see our guesses confirmed. The reason is simply cost - like most consumer PCs shipped today, they come with Windows. In terms of system design, it's cheaper to just include the limited memory and storage needed for 32-bit Windows. 64-bit Windows takes a lot more storage in particular. And on modern systems 32-bit Windows can only boot using 32-bit UEFI. Fair enough...

However, Brian goes on to state some more things that are simply out of date, saying that "Linux support for UEFI IA32 is still an unanswered question". Ummm, Brian: we've got working 32-bit x86 UEFI support in our standard Jessie (and newer) installation images already, and they work just fine on CD/DVD or USB stick. We've even gone one stage further than anybody else (thus far!) in adding easy support for running a full 64-bit Linux system on top of those 32-bit UEFI implementations.

I say "thus far" here because all the work here here is Free Software. Other folks added the support in Linux for making a 64-bit kernel work with a 32-bit UEFI; I added code in Linux to expose some of the details to userspace, and code in Grub to work with it. My changes have gone upstream already, so I'd expect to see other distros like Fedora or Ubuntu also using them soon.

00:40 :: # :: /debian/efi :: 1 comment

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Re: Justifying 32-bit UEFI on 64-bit Intel hardware, and tracking broken UEFI implementations
Christopher Price wrote on Fri, 07 Aug 2015 03:45

I posted some expanded commentary on the history of UEFI 32-bit and why we got to here with Bay Trail over on Brian's article.

I will say typically this boils down to kernel lag. The latest kernels handle Mixed Mode really well. The problem is most Linux distributions (even Intel-maintained ones like Tizen and Android-IA) suffer from kernel lag.

We all have to play a part in reducing kernel lag to make the latest hardware innovations (next up, USB-C for example) run well on Linux distributions.

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