Originally posted by esheep2001
The most widely accepted reason is the ability to handle twice as much data (64 bits instead of 32) in a single processor cycle.
Ordinarily this does equate to speed but in the case of the G5 (970) the architectural design allows for a transition from a 32 to 64 bit operating system by allowing existing 32 bit applications to run without modification. Hence these apps won't gain the speed advantage (other than through clock speed) until they are rebuit specially for the G5, and the OS will be hampered to some extent until all apps are built for 64 bits. This is the bug bear that people are talking about.
However you only need to look at the lacklustre market performace of the Itanium, which goes straight to 64 bits without the ability for transitioning, to see that the G5 (and AMD BTW) way is the best way as it keeps the largest number of people happy by allowing them to run all their favourite apps immediately. Itanium needs a special OS AND optimised apps (I believe) to run at all.
Basically what Apple have done is the equivalent of the 68k to PPC transition but without any of the pain.
Hope this helps.
e.
Errr... i feel like this is a futile battle to be fighting but I think youve got the wrong idea about how the 970 handles 32 bit legacy code. Rewriting apps is not a matter of making them 64bit apps so that theyll run in native mode. Its a matter of making the type of instructions, as well as the order of instructions conducive to fully utilizing all the parts of the processor so your task finishes in the fewest cycles. On the 970 a 32bit add takes the same number of cycles as a 64bit add if im not mistaken.
Now to answer that guys question as to the benefits of 64bit processors imagine this situation. You can only comprehend numbers up to 9 and you want to add the numbers 13 and 25 in this situation you would have to do the following steps.
Look at the last digit of the first number.. look at the last digit of the second number. add the two. write down whether the two numbers overflowed or added up to a number more than you can comprehend. Write down the part that didnt overflow, ie if they added to 6 write down six if they added to 16 also write down six. Look at the next digit of the first number. Look at the next digit of the second number. Add the two. Write down if they overflowed
.
You see where this is going
Now imagine you can comprehend numbers up to 1000. to add 13 and 25 you would look at the two numbers add then and write down the result.
So thats the very long, very convoluted way to say that 64bit processors are much faster at operations which you need to work with big numbers. Mathmatica could be one of those apps, certain physics calculations, encryption, and a whole bunch of other apps that no ones thought of making yet because up until very recently 64bit processors werent available to enough end users.
