Dual Core Processors

[bbcmicro]

This is extremely newbish but I wont learn if I don't ask.
Tee whole dual core processor thing has passed me by, I don't fully understand it. On the excrutiatingly dumbed down TV adverts it claims that it allows you to run more than one program, which doesn't make much sense to me as so have ordinary processors for years.

Is an intel dual core at around 1.2 Ghz more powerful than a single core 2.4 pentium, or what? How and why does a 1.2ghz dual core perform better than a 1.2ghz single?

I accept this is very basic stuff but please humour me.

[mbbrutman]

Let's look at this at a very low level. For the purposes of this discussion, we are only interested in the registers in the processor, not main memory.

A traditional processor (80486) runs exactly one piece of code at a time. That code is part of a process, or it might be operating system kernel code. But the main point is that it does 'one thing at a time', ie, when your program has control of the processor, the processor does nothing else. These processors have exactly one set of registers to use, and thus the limitation of only running one process at a time.

You are given the illusion of running many processes at a time because the operating system switches back and forth between the running processes many times per second. This is 'multi-tasking'. At any one point in time, only one process is on the processor, and everything else is waiting.

Newer 'threaded' processors have just one processor core, but more than one set of registers. Depending on the specific processor, these processors can handle two processes at the same time, however the processes share the processor core. How does this work? It's kind of like this ... while one process is active and busy on the core, the other can 'fill in' and use the parts of the processor that the first one is not using. It's not has fast as having two processors with each process having its own processor, but it is faster that just switching back and forth. This is available today as 'hardware threading', 'hyperthreading', etc.

Now let's talk dual core and quad core ...

It's just like having two processors in the machine. Except they both happen to be on the same chip. So you really can have two processes running at the same time, not just the illusion of it like we do on older processors.

Real life examples:

- You are playing an MP3 and web surfing. A traditional processor has to keep bouncing back and forth between WinAmp and Firefox. A dual core processor is actually like having two full processors, so both programs run at the same time.

- Photoshop: Photoshop and other good software knows how to use more than one processor. Your time to manipulate a picture might be twice as fast as it used to be now that you have twice as much cpu available.

Of course I'm simplying things greatly ... on a moder operating system there are many more processes running in the background than you need to care about, and the OS itself has to run quite often. But hopefully now you get the idea.


For a good example of this, look at the Cell processor in the PlayStation 3. It has 9 CPU cores on it. That's like having 9 full CPUs in the box. And yes, it's a !$#%! to do it right. :-)

[bbcmicro]

Ah, thankyou mbbrutman. It's all clear to me now. It was nice to read a clear explanation without any technobabble.

Cheers.

[carlsson]

To add a bit of speculation, I wonder when we're going to see 4-way, 8-way, 16-way, n-way processors? I know Sun Microsystems have some technology which has been reported that Intel (?) investigate very thoroughly.

[mbbrutman]

Cell is 9 way right now, with two different CPU instruction architectures on the same chip.

Intel has 'real' dual cores right now, and 'dual dual' cores (2 dual core processors bolted together) in their server line.

I'm sure that Intel, AMD, and IBM are thinking much bigger. It's relatively cheap bang for the buck. But software has to change to be able to use multiple cores at the same time. (ie: Start using threads, not just to handle the user interface but to split the real work up.)

[nige the hippy]

Intel is doing stuff with an 80 core processor, It's not 80 80XXX compatible chips but rather like an old "transputer" array.
If you do a search on intel 80 core processor, you'll get dozens of hits. quite exciting.

[carlsson]

Is it possible to obtain 80 simultaneous core dumps with a such processor? ;-)

[Vlad]

The Sun Ultra SPARC T1 has 8 cores. Thats the most I've ever seen in one shot.

[Dwight Elvey]

Hi
One other thing is that the newer processor are getting more done
per clock cycle. One has to be careful about comparing clock frequencies.
Any two different processors may be several times different in actual
speed for the same clock speed.
Don't expect to see clock speed go much beyond 3GHz anytime soon.
Power is becoming a limiting factor, requiring more done per clock
cycle, rather than faster clocks.
Dwight

[Mike Chambers]

multiple core is a pretty neat technology. my HP laptop is a dual core 1.66 ghz and even at that clock speed, tasks like encoding video with software that is designed for multiple cores is incredibly fast.

i have yet to upgrade my main desktop PC to dual core, i'm still using a 3.4 Ghz P4 w/ hyperthreading. it's a pretty decent chip, but i am still planning to put together a new machine soon.

i wouldn't mind having one of those intel quad core 3.66 ghz chips!;)

[Vlad]

I've been using this new laptop for a few days now and It's got a 1.86 Core Duo and I was rather surprised by the difference it made. I've worked with multi processor machines in the past, but that was all big iron. I'm surprised by how well Vista runs with a dual core processor. Its the first time I've really messed with a dual core other than poking at the displays at Staples. I'm surprise it doesn't run very hot, its actually quite cool...

[Unknown_K]

The only reason more cores are popular now is because they can't get single cored chips running above 4Ghz without melting.

I do like multiple CPUs ever since I ran my Dual PPro system on NT, but unless you run software that uses all the cores at the same time you will end up with cores just sitting idle. How many people run multiple programs at the same time that need a fast cpu for each task? It will take a long time before apps start using the multiple cores efficiently.

[Vlad]

Seems like Vista itself uses both cores to function looking at the Task Manager, plus I do 3D rendering and other CPU intensive work that dual core seems to enjoy, as well as me. :)

[Big Blues]

The only reason more cores are popular now is because they can't get single cored chips running above 4Ghz without melting.

I do like multiple CPUs ever since I ran my Dual PPro system on NT, but unless you run software that uses all the cores at the same time you will end up with cores just sitting idle. How many people run multiple programs at the same time that need a fast cpu for each task? It will take a long time before apps start using the multiple cores efficiently.

Even with software that doesn't utilize both cores, it's nice. When I got my dual core, my favourite part was that I could have one process chewing up one core, but still have a responsive system (even for simple tasks like popping up the start menu).

Joel