How to be sure if a processor is 32bits or 64bits ? Are dual core processors 32 or 64 bits?

Having a Macbook Pro with windows installed thanks to bootcamp, I have several questions:

• Under windows, I see that processes only use 50% maximum of the CPU charge, is that because the processor is a dual core and because the process is not开发者_如何学运维 multi-threaded ? Should I install windows xp version 64 bits instead, to have better performance ?

• Are all dual core processors 64 bits ? How can I check it with C or C++ to be sure that the native is 64 bits and not 32 bits ? I tried to print:

  sizeof(void*);

it says 8, so it would mean 64 bits, but I'm not sure...

• Does dual core explicitey means that if it has 2 32 bits cores, the processor itself supports 64bits instructions ? Is this the x86_64 architecture ?

• Is is delicate to emulate PS2 games because the original game has 128 bits instructions ?

• Why are long double 128 bits while

  sizeof(long long); sizeof(long);

both output the same thing ?

• Yes 50% is maximum use for a single thread. No 64 bits won't change anything to that.
• All Core 2 and Core i* processors are 64 bits. All Atoms are 32 bits. Your sizeof is correct, though it won't help if you compile as 32 bits app on a 64 bits system.
• 2x 32 bits doesn't equal 64 bits. A 64 bits processor has 64 bits cores, a 32 bits processor has 32 bits cores.
• It makes the emulation slow, but the difficulty comes from the complexity of the PS2 architecture, and from the differences with a PC. Plus, it might not be very well publicly documented, so finding specifics can be hard.
• Ask the specs. Some types have sizes that are platform-dependent, which means an int might be 64 bits or 32 bits or even 16 bits.

With Mac OS Snow Leopard with run application in 64-bit if the universal binary has 64-bit code, otherwise it loads the 32-bit code. Also you can decided if you want Snow Leopard to load OS full with fill "64-bit Kernel & Extensions" at boot up. I have my MBP set to boot 64-bit.
Which MacBookPro can boot into 64-bit

Now, for the Windows on Boot Camp. Whatever version you have of Windows installed will dicate if it 32-bit or 64-bit. So unless you install the 64-bit version of Windows you won;t get 64-bit. Whereas, Snow Leopard has it built-in for both 32-bit & 64-bit. And you cannot upgrade for example Windows XP 32-bit to Windows XP 64-bit. You will have to install from scratch.