I've been working on the list of supported platforms for Firefox 4 and wanted to provide an update on some decisions that have been reached.
* In February of this year, there was a discussion  in which we decided that the minimum supported version of Mac OS X would be 10.5 (Leopard)
* Early in the summer we decided to not yet provide supported 64-bit builds on Windows , and will instead work on delivering those in some future release.
* In July we decided that the minimum supported version of Windows would be Windows 2000 
* After some evaluation  we decided this week to drop support for OSX/PPC; Firefox 4 Mac OS X binaries will ship as universal builds for i386/x86-64 only
* We are considering dropping support for i386 architectures which do not support SSE2  (older Athlon CPUs, some VIA chipsets) but have not yet reached a final decision here.
I will maintain a de-facto list on this page: https://wiki.mozilla.org/Firefox/4/Platforms
: I can't find the link, so if you'd like to, treat this post or https://wiki.mozilla.org/Firefox/4/Platforms as canonical!
> * We are considering dropping support for i386 architectures which do not
> support SSE2  (older Athlon CPUs, some VIA chipsets) but have not yet
> reached a final decision here.
There was a thread on this back in December. I think the outcome was that
it was a clear "collect more data".
On an anecdotal note, I know of several machines still in active use (some
even that have just even have just been updated do windows 7) that would be
disadvantaged by this change. Diverging from OS requirements (as I stated
before, Windows 7 supports non-sse2 systems) could be confusing.
That's amazing how many people still run Firefox on a PIII. Also a lot
I wonder if the only day they'll stop using their computer is when
Firefox won't run anymore on it ;-)
So, does that mean 386 or SSE2? SSE2 goes much further than 386 - it
includes all Pentiums until P4 as well.
Well, people have only been asking for that since 2008. So, no
(Are you KIDDING? I hope this is just a bad joke.)
Performance of 32-bit vs 64-bit code really depends on the workload; for
a lot of things we do the extra registers make a noticeable difference
and we get a speedup (even in spite of the higher cache pressure 64-bit
Last I measured, for DOM operations we're talking about 20%, at least on
This isn't on-topic for this thread. Please stop.