misr12 said:
How much of the operating system will OSX (tiger) 10.4 be 64 bit on G5's? Will we see any noticeable boost in overall OS and application use? I never really understood the benefits to the end user. Can someone explain? Are we looking for lag/delay from programers to catchup with the hardware?
Well "64 bit" can mean lots of things...
The version of Mac OS X and related developer tools that was release with the Power Mac G5 systems allowed the developers to use the 64 bit general math capabilities (floating point has always supported 64 bit on PPC) of the G5 processor. In Panther aspects of system libraries, etc. got enhanced to utilize the 64 bit general math capabilities as well as aspects of applications both from Apple and 3rd parties (PhotoShop for example).
Depending on what an application is doing... a conversion to using 64 bit math capabilities can (not will) result in a slightly better then 2x improvement over doing two or more 32 bit operations on the same 64 bit value (slightly better then 2x because of less interdependent instructions potentially bubbling the pipeline).
Expect Tiger to take optimization for the G5 much farther then what was seen in Panther (this includes more use of 64 bit math abilities among several other things). This includes system provided libraries and frameworks that existing application use, so even existing application will benefit without any rework.
Mac OS X as of the Power Mac G5 systems has the ability at the memory sub-system level to address greater then 32 bits worth of physical RAM (4 GB) and that is why the PM G5 and Xserve G5 systems can take 8 or 16 GB of physical RAM (the PPC 970 and memory controller has hardware to support this).
However virtual address is still limited to 32 bit (4 GB) and that is often sufficient for a vast majority of applications at this time. The ability to have greater then 4GB of physical RAM basically allows one to run more applications that consume a majority of their 4GB virtual address space as well as allows the UBC (universal buffer cache) to cache more data avoiding disk access which are very slow compared to memory access.
Tiger will add the ability for command line process to use a 64 bit virtual address space (see my prior post about this) which is over 4 billion times larger then a 32 bit address space.
Important thing to note is that Tiger will support both 32 bit and 64 bit addressing in the same release, you won't have to buy a 64 bit or 32 bit version of Tiger.