On 08/23/2011 10:37 PM Drew wrote:
What determines if it's a 64 bit machine? Dual core?
Dual core = 2 CPUs effectively. Quad core = 4 CPUs on the same piece of Silicon
64 bit = more advance instruction set which replaces all the older 32 bit instruction set CPUs. 64 bit is more modern than 32 bit and that is the way software is going.
64bit doesn't specifically make it "more advanced." 64bit CPU's just support for a larger memory addressing space then 32bit CPU's, beyond the 4GB limit of 32bit addresses.
64-bit processors can deliver 64 bits of data at a time to all peripherals, not just memory. By contrast, 32-bit processors can deliver at most 32 bits to any peripheral, then as a second step deliver the next 32 bits. So, AOTBE, it takes twice as long to shoot data down the bus. That's outgoing. Same applies to data coming into the processor. I haven't looked up and compared the lists of instructions on 32- vs. 64-bit CPUs, but generally the bigger processors have more, and more sophisticated, instructions. This means, e.g., that instead of taking 20 steps to do a calculation on a 32-bit CPU, it might be done in 5 steps on a 64-bit. There might also be larger L2 and L3 caches on the larger processors (but this also varies within the 32-bit and within the 64-bit families).
All that said, I still use a five-year-old 686... as both a server and a client. It runs apache, mysql, and several other servers apps, plus the full range of client applications... most of the time I'm using about 2% of the CPU's power. I've worked in places where I've had access to 80 or so servers and most of them never used more than 5% of their CPU's processing time... kind of a waste... in several ways. So unless you really need the big, f*'ing CPU, why diddle away your cash?