Difference between 64 and 32 bit processors?

[imgod2u]

Not really, the "bitness" in most consoles actually refers to the "bitness" of the CPU inside it. Of course, modern consoles (most notably the PS2) stray so far from the conventional PC-like design (a CPU and a GPU, main memory, etc.) that it's difficult to label a "bitness".

 

[DaddyB]

Jaguar is old and was made by Atari if memory serves (old meaning SNES days or thereabouts), I don't recall if it was 64bit or not. Dreamcast was Sega's newest console and was 128bit according to this and the saturn was 32bit but had 3 processors.

Back to the original topic, what is the difference between 32 bit and 64 bit then? Just that it can address more RAM (keep in mind he isn't asking about x86-64/amd64, just in general)?

I'd say the difference are that it can handle more RAM and the ALU can handle large intergers faster/more efficiently. Anyone disagree with that?

BTW I used the link to Tom's because it is the only bench I have seen that compares the 32bit and 64bit modes of the Opie and when there is a 3.6Ghz 32 bit AMD CPU I will agree that it can handle an equal numer of 64 bit ops in the same amount of time ( not clock cycles) as the 1.8Ghz Opie (in 64bit mode).

 

[Movax]

I haven't looked at any specs for any of the new CPUs (The Apple PowerPC or Opteron) But 64-bit can mean a lot of things. Internal data bus, External Data bus, instruction size, operand, register size, ALU, etc. Saying that your CPU is 64-bit doesn't really mean much.

How many bits are there for the address bus on the G5? I don't see exactly where 64-bit = 8 GB of memory.

64-bit can be faster, and slower. Depends on the code.

But, unless IBM and AMD are lying and/or really stupid corporations with money to waste on something because it sounds good for their marketing depts, I would tend to think that 64-bit will be faster.

 

[gamefoo21]

people see "64-Bit Capable" and they think its better than a p4 its all a marketing scheme now-a-days. so ppl buy therefore making the companies mo money.

 

[Arkaine23]

The lowdown

The biggest difference is that 32 bit CPU's can only address 4GB of ram at one time, while 64 bit CPU's can address up to 64GB of ram (assuming a mobo is built with 64 slots for 1GB ram sticks).

G5's are not true 64 bit CPU's, but neither are they 32 bit CPU's. I think they support as much as 8GB of ram.

Opterons- AMD 64 bit CPU's offer a very fast interface from CPU to ram since the memory controller is built-in to the CPU. There's very low latency. So better performace even if the CPU clock speed is low. Also, they are available with varying amounts of L2 cache- from 512kb to 1.5mb.

 

[Hedgehogforprez]

Re: The lowdown

(assuming a mobo is built with 64 slots for 1GB ram sticks).

Or simply just 32 slots where one could fit 32 2gb sticks That would get rather spendy but correct me if I am wrong, couldn't SMP allow more memory or am I just delusional?

 

[imgod2u]

No, it couldn't. Even in SMP, the programming model remains the same. There is only 1 memory address space at any given time.

 

[druidelder]

If workstations are desktops, then I think Sun/Digital/etc... had Intel/AMD/Apple beat.

Two processors are not worthless on a personal computer (16,32,64,1024bit or otherwise), unless you only run one or two apps at a time. Macs have long been the domain of graphic artists, digital musicians, video editors, etc.... These programs can put a strain on a single processor (particullarly with large files). The second processor allows you to be able to run other things at the same time without a performance hit.

That's why we have the SMP section.

 

[Michal[mt]]

new technology is expensive. old technology is overclockable

Nice statement Pixel

There is no need to introduce a 64bit architecture at this time guys. Marketing and business never brought significant innovations.

 

[OC Detective]

Nice statement Pixel

There is no need to introduce a 64bit architecture at this time guys. Marketing and business never brought significant innovations.

I take it you are confining that statement to cpus. The Walkman (extremely innovative at the time) is one of many products that only became popular through market push as opposed to demand pull and that spawned many spin off products..

 

[druidelder]

A note about RAM addressability, the maximum amount of RAM a processor supports is determined by the Address Bus Width. This is not determined by the "bitness" of the processor. From the 386DX to the Pentium MMX (on the Intel side any way), the ABW was 32 bits, allowing for a maximum of 4GB system RAM. The Pentium Pro and Pentium II (and I would imagine later processors as well) had an ABW of 36 bits, allowing for a maximum of 64GB of system RAM. The maximum memory supported by a system is usually throttled by the chipset (not the processor).

The 4GB barrier is the maximum cacheable memory. A system can have more physical memory than the cacheable memory, but at a performance hit (5-25%). Until the Pentium Pro, the chipset determined what the cacheable limit was (this is determined by the length of the tag RAM which is part of the L2 cache). Since that time the L2 cache has been integrated on the chip and control for maximum cacheable RAM has moved to the processor. The Pentium Pro could cache up to 4GB, but the Pentium II could only cache 512MB.

You may already know this, but I thought I'd throw in a history lesson for those that didn't.

 

[dippy_skoodlez]

My friend brought up to me that the Mac G5 has a 64bit processor but niether of us knew the difference between that and a 32 bit processor.

I was thinking the athlon mp(?) series was a server series that used 64bit processors. Also, the G5 has two processors. They advertise the G5 as a personal computer, but it seems to be more of a server. Aren't two processors practically worthless on a personal computer?

The macs are different. run TOTALLY different codes, and most G4's have dual Proc's. thus, most/ a LoT of the higher end/main macs have dual CPU's. so, most programs can take advantage of it.