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64-bit desktop ISO vs 32-bit desktop ISO: EFI vs legacy boot mode

rated 0 times [ 1] [ 0] / answers: 1 / hits: 2757 / 2 Years ago, sat, april 9, 2022, 7:55:11

So my understanding is that Ubuntu desktop 13.04 ISO comes in two flavors:

32-bit (supporting only legacy boot mode)

64-bit (supporting only EFI boot)

Is this correct? What I want is a single bootable image that will boot on both my legacy computer and my newer computer. They both currently run 64-bit software, but I can't get the 64-bit image to boot on my older computer.

I don't really care if I run 32-bit or 64-bit Ubuntu, what I do care about is using the same USB stick for either computer. Is there an easy way to get the 64-bit image bootable in legacy boot mode for my older computer? Or is there an easy way to get the 32-bit image bootable under UEFI on my newer computer?

Or, if the 64-bit image should just work in legacy boot mode, please let me know.

Thanks.

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antebrow

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answered 2 Years ago looweets · Accepted Answer

The 32-bit Ubuntu is BIOS (legacy) only, whereas the 64-bit Ubuntu supports both BIOS and EFI boot modes. Thus, the 64-bit image should work on your older computer, provided that computer has a 64-bit CPU. The x86-64 (aka AMD64, x64, or EM64T) architecture dates to 2003 (with AMD's Opteron line), but it started to become popular a couple of years after that. Even today, some computers still use 32-bit CPUs, although they're mostly low-end or embedded devices. Thus, without further details, it's unclear whether your older computer is 32- or 64-bit.

The 32-bit Ubuntu should run on 64-bit computers, including most EFI-based systems; however, to boot on an EFI-based computer, a BIOS-based OS (including standard 32-bit Ubuntu live CD/USB images) requires that the EFI have a feature known as the Compatibility Support Module (CSM), which is a BIOS-compatibility layer. Most modern EFIs have this feature, but it's often disabled by default, so you may need to enter your firmware setup utility to enable the CSM (aka "legacy mode" or "BIOS mode"). The details of how to do this vary wildly from one EFI to another, so it's impossible to give simple and accurate instructions for doing so that apply to all computers.