Shoutbox

Actually, I'm not 100% sure that 64 bit processors actually use larger numbers, I believe this to be a common misconception.

Let me show you my reasoning:

Maximum Addressable Memory = 2 ^ Size of Address Bus
Maximum Size of Memory = (2 ^ Size of Address Bus) * Size of Data Bus

Now, the Maximum Size of Memory in a 32 bit machine is 2^32 bytes, aka an Address Bus size of 32 bits and a Data Bus size of 8 bits (1 byte = 8 bits).
Also, the Maximum Size of Memory in a 64 bit machine is 2^64 bytes, aka an Address Bus size of 64 bits and a Data Bus size of 8 bits.

Btw, if you didn't know, the Address Bus is used to address memory locations in RAM (memory is used to refer to working memory, ie RAM, not backing storage, such as the space on a Hard Disk Drive), and the Data Bus transfers data to and from the processor.

So, as you can see, a 32 bit processor has an 8-bit data bus, but so does a 64 bit processor. So a 32 bit processor in essence is no slower than a 64 bit one.

BUT: A 32-bit processor is limited to 4GB of RAM, whereas a 64-bit processor is limited to something like 16EB. Now, in todays world, most PCs only have 1GB of memory modules installed so there isn't a problem.

64-bit processors are actually slower when it comes to things like pointers, but that's a really technical thing, you don't need to worry about it.


So basically, on a 32vs64 bit processor system, there is no difference in current machines. But the instruction set differs between a 32bit AMD and a 64bit one, and these extra instruction sets give the 64bit processors an advantage. And it's always been said that MHz for MHz, AMD processors are much faster (the actual number (such as 3700+) for an AMD processor isn't it's actual clock speed, it's the comparison in speed to a P4 processor).

Now, if I were basing my choice, I'd be stuck. AMD have just introduced the AM2 socket, which means that the 939-pin processor line will be effectively dead within 2-3 years, and people will be using the 940-pin socket. Of course, with a 939-pin motherboard you can still upgrade to things like AMD's X2 4800+ processors, as those are designed for 939-pin motherboards atm.

I think Intel have started releasing 64-bit processors, so buying a 32-bit motherboard now may limit your options for upgrade even closer in the future.

Update: Forgot to mention cache size, I think AMD 64s of that line have 1MB L2 cache and the Dual-P4s have 1MB per core, so the P4 would be faster in that capacity. (Cache is lightning fast SRAM stored close the the processor and stores commonly used instructions).