So, I laid my hands on Swiftweasel, which is open source and optimzed build of Firefox for Linux. It lets you download processor specific optimized builds. So I installed build for Pentium 4 M and I could see some noticeable speed differences 🙂
Swiftweasel is a free and open source build of Mozilla Firefox. It is licensed under the MPL 1.1 and uses free graphics and logos. It is optimized for several architectures, and is available for Linux only. Mozilla Firefox plugins, extensions, and themes are fully compatible with Swiftweasel.
Differences from a regular firefox build
Binary code optimization
* Compiled with options that optimize for speed rather than binary size.
– Swiftweasel is compiled -O3, (the highest level)
– The resulting Swiftweasel binary is larger than Firefox.
– Firefox is compiled -Os (which is for binary size).
* Binaries incorporate additional instruction sets.
– Intel and AMD: SSE2, SSE, SSE3, and MMX.
– AMD only: 3DNow!
* Optimization specific to the build microprocessor architecture.
– Intel 32bit: Pentium 4, Pentium 3, Pentium M, Pentium 3M, Pentium 2, Prescott.
– Intel 64bit: Nocona
– AMD: Athlon XP, Athlon, K6-2.
– AMD64: Athlon64, Opteron
* Compiled with newer version of GCC (Firefox 2.0 uses 3.3.2, Swiftweasel 2.0 uses 4.0.3).
* Better protection from Buffer overflow attacks(Swiftweasel 2.0 uses -D_FORTIFY_SOURCE=2; Firefox 2.0 uses gcc 3.x, which does not support this).
* Pango is included in the build to improve rendering.
* IPv6 DNS lookups are disabled, preventing slowdowns.
* HTTP pipelining is enabled by default. Note that Fasterfox provides a GUI to adjust these settings.
* For full details, users can download source packages with all changes listed.
– shamelessly copied from http://en.wikipedia.org/wiki/Swiftweasel
It looks to be alone the lines of SwiftFox, which is a freely downloadable, *proprietary graphical web browser.* Looking more into the license, “the Swiftfox binaries have a proprietary license which does not allow redistribution.” which means it cannot be called a free software. Moreover it does not support all Forefox plugins. So, swiftweasel is a fully open build of the Mozilla Firefox code, without proprietary graphics and license like Swiftfox. Exactly what the doctor ordered.
So go on and have a look yourself.
Similarly there is a free optimized SwiftDove, which is optimized build of Mozilla ThunderBird.
Download from here : http://sourceforge.net/project/showfiles.php?group_id=195473