I am having trouble finding a clear answer to this silly question. Are all Macbook Pros 64bit ? Even those Core Duos that were first released ? Are there any Macbook Pros that are 32bit ?
Yes, the Core 2 Duo is 64-bit meaning it can address 64-bits of memory.
In short, the Core brand refers to processors with the "mobile" derivative of 32-bit Intel P6 microarchitecture (preceding the Core microarchitecture), whereas the Intel Core 2 Duo brand refers to CPUs with the 64-bit Core microarchitecture.
All MBP use 64 bit CPU's even the core duo's. The update was to the motherboard (Santa Rosa). Though if you look at the benchmarks the update was not impressive at all. The speed increase in many processing benchmarks on a system that was 32 bit motherboard compared to 64 bit motherboard were like 1 second in speed increase over the 32 bit. Kind of sad.