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Computerworld - Mozilla this week said it's unlikely that the final version of Firefox 4 will run on older Macs equipped with PowerPC processors.

"We are not likely to be supporting PowerPC," said Mike Beltzner, director of Firefox, in a message Tuesday on the Mozilla.dev.planning discussion group. "[But] no announcement has been made yet, as I'd like to have the data to back it up, and am having trouble getting it."

Later on Thursday, a Mozilla spokeswoman confirmed that the company is discussing ending support for the PowerPC, and said it would announce its decision shortly.

Apple discarded IBM's PowerPC architecture in 2005 when it announced it was shifting to Intel processors. The first Intel Macs launched in January 2006.

Mozilla shipped the fourth Firefox 4 beta two days ago and has tentatively set a final release for November.

But the beta doesn't work on PowerPC, said one developer, whose report that the browser was "totally broken" on his older Mac prompted Beltzner to confirm that Mozilla might pull support for the processor.

The biggest stumbling blocks to PowerPC support are an anticrash technology dubbed "out of process plug-ins," or OOPP -- which is designed to keep the browser up and running when some plug-ins drop dead -- and the just-in-time compiler (JIT) used in Mozilla's new JaegerMonkey JavaScript engine. Both are key components of Firefox 4.

"Firefox should be fast, responsive and secure," said Beltzner in a message posted Wednesday to the same discussion. "We cannot deliver that on PPC [PowerPC] anymore since we don't have support for the JIT on PPC, nor do we have support for OOPP."

Mozilla has not yet spelled out system requirements for Firefox 4. Instead, it directs users to those for Firefox 3.6.

Beltzner said others could build browsers for Linux that support PowerPC using the Gecko 2.0 engine, the same that powers Firefox 4, probably by disabling the OOPP and JIT code. But those browsers probably wouldn't carry the "Firefox" name.

One such possibility for PowerPC Macs might be Camino, an open-source project that develops a Mac-only browser based on Mozilla's Gecko. Camino, which is currently at Version 2.0.3, runs on both Intel- and PowerPC-equipped Macs but relies on the older 1.9 Gecko engine.

Mike Pinkerton, a Google engineer who heads the all-volunteer Camino project, did not reply to questions about the browser's future plans to support PowerPC, but they may be in doubt: Notes for a Wednesday status meeting include the line "Gecko 2.0 [formerly known as] 1.9.3 -- on ice."

Earlier this year, Mozilla dropped support for Mac OS X 10.4, a.k.a. Tiger, for future versions of Firefox, saying that Firefox 3.6, which launched in January, would be the last to be officially supported on the five-year-old operating system

Apple ceased updating Tiger almost three years ago.

The newest version of Mac OS, Snow Leopard, requires an Intel-based Mac.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, or subscribe to Gregg's RSS feed . His e-mail address is gkeizer@ix.netcom.com.

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