Originally posted by G4scott
Ok, let me see if I'm right... A 32 bit OS or App could run on a 64 bit chip, but it would only process 32 bits at a time, meaning the processor is running at a 50% performance level.
Now, to have a 32 bit app take advantage of a 64 bit processor, would it be possible to have the processor put two 32 bit commands in each clock cycle? Isn't this how Apple was able to say that Velocity Engine could process data in 128 bit chunks, because in reality, it just does 4 32 bit chunks per cycle?
So, 32 bit apps will work with a 64 bit chip, right? Well, if an app was to take true advantage of that chip, rather than just work with it, it would have to be changed to a 64 bit app, right? But this change would be only to optimize it, because it would run ok without it... This is how I see it, based on some of the stuff I've been reading here...
Not really correct. The processor is an eight way superscalar design meaning it's going to get eight ops out per cycle whether or not they are 32 or 64 bit precision.
The real advantage of 64bit processors is that using 64bits exponentially raises your ability to address memory. So you move beyond 32 bit memory limits.