The Register claims that Appleis forthcoming operating system, OS X 10.3 (Panther) will be a "bit" less than people expect... 32 bits to be exact.
In a somewhat tech-heavy article, Tony Smith explains that Panther will be similar to OS X 10.2.7 (currently running on the pre-production PowerMac G5) in that it will only contain limited amounts of 64-bit enabled code. It is this code that will allow current software to use the new features of the G5 chip. From the article:
Smeagol [OS X 10.2.7] is a 32-bit operating system, though certain libraries and other elements have been recoded to allow applications - and the OS itself - to make use of the 64-bit addressing and datapaths, sources close to Apple said. For example, thatis how the Power Mac G5 is able to support at least 8GB of memory, double the 32-bit limit of 4GB. Panther will adopt the same approach.
The upshot that a 32-bit app can gain access to a much larger address space than it by rights is able to, though it has to be optimised for the 970 first
This level of backwards compatibility with 32-bit programs is only possible because the new G5 processor already has the capability built-in. The importance of such a feature should not be overlooked as it allows Apple to make a smooth transition from one major architecture to another.
This approach is clearly the one Apple favours, and the inclusion of the "temporary" bridge technology in the 970 may well have been made at Appleis behest. This way Apple and its developers can take advantage of the 970is 64-bit addressing and datapaths without having to maintain a new codebase for the G5 alongside code intended to be run on older processors. "All applications written for 32-bit implementations will run without modification on 64-bit processors running in 32-bit mode," says IBMis documentation.
Itis possible that Apple may be in the early stages of a complete shift to 64-bit processors. According to IBM documents, 32-bit capability will not be in the Power PC line indefinitely. "These resources are not to be considered a permanent part of the PowerPC architecture."