Firefox 2 patched for the A9homePublished: 3rd Dec 2006, 17:20:50 | Permalink | Printable
Cunning coder cheats check for XScale [Updated]A cheeky programmer has produced an unofficial patch to allow the previously Iyonix-only Firefox 2 port to run on A9home computers. The hack intercepts low level ARMv5 instructions that the Iyonix's IOP321 XScale can execute, and converts them into instructions suitable for the ARMv4 Samsung ARM920T processor in the A9home. The patch, which runs as a module, was written overnight by NetSurf GTK developer Rob Kendrick.
Joking that he was after a grand in donations for his patch work, Rob said: "I wanted to see how well Firefox 2 performed on the A9home, but Peter had decided for some reason to intentionally nobble it to run only on the Iyonix."
Rob added that some ARMv5 instructions are not properly emulated, which will lead to images being displayed incorrectly - although these bugs are expected to be fixed in later releases of the module.
He said: "I may well be incorrectly implementing SMUL, and that it's used in image decoding, which is why they're corrupted. But the performance of it is acceptable - it certainly feels just as quick, if not quicker than it did on David Ruck's Iyonix at the Midlands 2006 show, amusingly."
Click on a thumbnail for a larger picture
A9home users must download both a patched Firefox executable and the ARMv5 emulator - the Firefox application checks to make sure it is running on an XScale, which Rob also removed. The ARMv5 emulator works by hooking into the undefined instruction processor vector, catching the ARMv5 instructions before RISC OS 4.42 on the A9home traps it.
Firefox 2 port developer Peter Naulls said he would consider an official A9home version if there was sufficient financial interest. It's understood the Firefox 2 port was built with ARMv5 instructions to squeeze extra performance out of the mammoth web browser on the Iyonix.
Update at 22:26 6/12/2006
Version 0.03 of the ARMv5 emulator has been released with various big fixes and enhancements. Rob has also noted that the ARMv5 instructions in Firefox 2 afford a mere thousandth of a second speed increase in a simple test with the BBC News website.
Patched Firefox 2 A9home binary
ARMv5 emulator module - source included
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