> using a 64 bit kernel makes a huge difference in a system
I do actually use a 64bit kernel with 32bit userland. With Fat binaries I would not have to give a shit one way or the other.
> but unless a single application uses more than 3G of ram it usually won't matter much to the app if it's 32 bit or 64 bit. there are some apps where it will matter, but those are special cases and probably not where a universal binary would be applicable.
Here are some issues:
* The fat binary solves the problems you run into with the transition process of moving to a 64bit system. This makes it easier for users and Linux distribution developers to cover all the multitude of corner cases. For example: Installing 'Pure 64' versions of Linux for a period of time meant that you had to give up the ability to run OpenOffice.org. This is solved now, but it's certainly not a isolated issue.
* People who actually need to run 64bit software for performance enhancements or memory requirements will have their applications 'just work' (completely regardless to whether they were 32bit or 64bit) with no requirements for complicated multi-lib setups, chroots, and other games that users have to solve. They just install it and it will 'just work'.
* Currently; If you do not need 64bit compatibility now you will probably want to install only 32bit binaries. However if in the future you run into software that requires 64bit compatibility. With the status quo it would require you to re-install the OS
* Distributions would not have to supply multiple copies of the same software packages in order to support the arches they need to support.
* Application developers (both OSS and otherwise) can devote their time more efficiently to meet the needs of their users and can treat 64bit compatibility as a optional feature that they can support when it's appropriate for them rather then being forced to move to 64bit as dictated by Linux OS design limitations.
Yeah FAT binaries only really solve 'special cases' issues with supporting multiple arches, but the number of special cases are actually high and diverse. When you examine the business market were everybody uses custom in-house software then the special cases are even more numerous then the typical problems you run into with home users.
Sure it's not absolutely required and there are lots of work arounds for each issue you run into. On a scale of 1-10 in terms of importance (were 10 is most important, and 1 is least) it ranks about a 3 or a 4, But the point is that FAT binaries is simply a superior technical solution then what we have right now, would solve a lot of usability issues, and comes from a application developer that has to deal with _real_world_ issues caused by lack of fat binaries that works with software that is really desirable for a significant number of potential Linux users.
He would of not spent all this time and effort into implementing FatElf if it did not solve a severe issue for him.