The Definitive Dual Processor (crap, Dual Core) Definition

[Cromulent]

Both the processors in the 9600 are on a daughtercard, together, that plugs into the motherboard. The L2 cache is located on the motherboard, not the daughtercard. Both processors share the same bus and cache. I said that like ten times. I'm not getting this off Apple's web site, but from fact. I have several 9500s, 8600s, and had a few 9600s before. I know what I'm talking about, ask anybody that used one of these before.

If the two processors do not look like the picture below it is not a dual core system it is a dual processor system.

And everything you're saying about a dual-core system "not having two processors" is just nonsense. You're telling us that if somebody with a "dual core" Mac says they have two processors, you would tell them that they do not. That's just dumb.

When did I say they did not have two processors. In the three definitions I posted it clearly stated the fact that a dual core system is a computer with two processors on the same chip.

I guess the sticking point here is the fact that you seem to be obsessed with the idea of using your own terms to describe something. That description is misleading as I have already pointed out numerous times.

The difference between a dual core system and a dual processor system (which I will repeat for the last time) is that a dual processor system is a computer with two independent processsors where as a dual core system is a computer with two processors on the same chip.

I still do not see what is so hard to understand about this. A Mac Pro is a dual processor dual core system which totals 4 cores. Each core is a separate processor but there are only two chips within the computer itself. The two processors with each chip are mearged into one as you can see in the picture below :

this has two processors contained within it. But as you can see it is clearly one chip taking up one CPU socket on the motherboard.

If you had two single core CPUs in the same computer it is a dual processor system. If you have one dual core CPU in the system it is a dual core system. If you have two dual core CPUs in the system it is a dual core dual processor system which means it has 4 cores in total but only two physical chips contained within it.

 

[dpaanlka]

Not having read the thread, I would say that 1 CPU = any number of cores in a single die. This is because a CPU is a Central Processing UNIT. That means that the entire UNIT (ie, the chip) is the CPU, because the term 'unit' covers everything in/on a chip.

The definition of "CPU" was never the topic here. "CPU" does not equal "processor" nor does it equal "core."

When did I say they did not have two processors. In the three definitions I posted it clearly stated the fact that a dual core system is a computer with two processors on the same chip.

I guess the sticking point here is the fact that you seem to be obsessed with the idea of using your own terms to describe something. That description is misleading as I have already pointed out numerous times.

What? I've been saying this entire time that a "dual core" Mac should still be considered as having two processors.

Frankly, I don't even know what we're talking about anymore. So you agree that the MacBook has two processors and the Mac Pro has four?

 

[Cromulent]

What? I've been saying this entire time that a "dual core" Mac should still be considered as having two processors.

Frankly, I don't even know what we're talking about anymore. So you agree that the MacBook has two processors and the Mac Pro has four?

Yes but saying the MacBook is a dual processor machine is wrong. As that would imply that it has two separate processors. It is a dual core machine. Now using the definitions I have already provided that means it is a computer with two processors on the same chip. That is all I am trying to say. It is about using the correct words to describe the machine.

These terms are not interchangeable as I have been trying to point out to you for this entire thread. They are used to describe two completely different things.

 

[dpaanlka]

These terms are not interchangeable as I have been trying to point out to you for this entire thread. They are used to describe two completely different things.

This entire thread you've been telling me the current definition of the terms. I already know what they currently stand for, I am saying they shouldn't mean that - because there are two processors in a MacBook.

Nothing you've said has been an actual reason why anybody cannot refer to their two processors as dual processors. Because they're on one die? So! They're still two processors. That doesn't change anything at all!

You just keep giving me the definition as it is currently accepted to be and saying "this is how you have to interpret it." Well, I'm not interpreting it that way. It really just sounds like Intel marketing.

And regardless, earlier in the thread you were saying the definition of dual core is two processors sharing the same bus and cache. You've actually changed your definition through the course of this thread. I really don't you're listening to what I or bearbo is saying.

 

[Cromulent]

This entire thread you've been telling me the current definition of the terms. I already know what they currently stand for, I am saying they shouldn't mean that - because there are two processors in a MacBook.

Nothing you've said has been an actual reason why anybody cannot refer to their two processors as dual processors. Because they're on one die? So! They're still two processors. That doesn't change anything at all!

You just keep giving me the definition as it is currently accepted to be and saying "this is how you have to interpret it." Well, I'm not interpreting it that way. It really just sounds like Intel marketing.

And regardless, earlier in the thread you were saying the definition of dual core is two processors sharing the same bus and cache. You've actually changed your definition through the course of this thread. I really don't you're listening to what I or bearbo is saying.

Have you just ignored all the others who posted in this thread stating the same thing as me, including one who works in the industry? I really do not understand how you can not understand the need for two different descriptions.

One is on the same chip the other is two separate processors. They are a completely different architecture. What would be the result of calling them the same thing? Confusion that would be the result.

Talking about CPUs is already a confusing subject what with talking about clock speeds, socket type, upgrade ability, which RAM is compatible with which CPU and so on. Why make it even more confusing by eliminating a phrase used to tell the difference between two different architectures.

Oh and by the way, on the basis of this thread I have decided to call all Apple Macs PCs because the Apple Mac name is just a marketing term. Everyone will know I mean an Apple Mac when I say it because my use of the term makes more sense than everyone else's. Obviously this is the correct usage of the term as they are both Personal Computers and the only reason people call Apple computers Macs is because of marketing spin.

Sorry for the sarcastic paragraph above but that is basically the argument that you are using. Of course I would be correct to call an Apple Mac a PC, but the point is people tend not too in order to avoid confusion. A PC is generally accepted as being a computer running Windows on either Intel or AMD hardware. Where as a Mac is a computer running OS X on IBM/Motorola or Intel hardware.

That is why it is important to differentiate between dual core and dual processor.

 

[dpaanlka]

Have you just ignored all the others who posted in this thread stating the same thing as me

Have you ignored mine? What about where I said "why don't they come up with a different name that doesn't suggest other systems with two processors somehow do not have two cores." They do, after all, have two cores.

I really do not understand how you can not understand the need for two different descriptions.

Frankly I don't understand what you don't understand. All the systems in question have two processors and two cores. "Dual core" is a bad name to call two processors on a single die, because all two processor systems have two cores. What about that don't you get?

What would be the result of calling them the same thing? Confusion that would be the result.

I really think calling them dual core, when every other two-processor system also has dual cores, is more confusing than clarifying.

Talking about CPUs is already a confusing subject what with talking about clock speeds, socket type, upgrade ability, which RAM is compatible with which CPU and so on. Why make it even more confusing by eliminating a phrase used to tell the difference between two different architectures.

Because the phrase itself is confusing. It leaves the impression that only the systems specifically labeled as "dual core" have two cores, when in reality, every system with two processors has dual cores, regardless of how the chips interface with each other.

Sorry for the sarcastic paragraph above but that is basically the argument that you are using. Of course I would be correct to call an Apple Mac a PC, but the point is people tend not too in order to avoid confusion. A PC is generally accepted as being a computer running Windows on either Intel or AMD hardware. Where as a Mac is a computer running OS X on IBM/Motorola or Intel hardware.

Yes, but "Mac" can in no way be confused with "PC" - all computers that fit on or around a desk are "PCs" - but only computers made by Apple are Macs. However, in our examples, every system has both two processors and two cores. Completely different, because "core" and "processor" go together. If you have two cores, you have to have two processors, and visa-versa. They cannot be separated.

 

[bearbo]

Have you just ignored all the others who posted in this thread stating the same thing as me, including one who works in the industry? I really do not understand how you can not understand the need for two different descriptions.

One is on the same chip the other is two separate processors. They are a completely different architecture. What would be the result of calling them the same thing? Confusion that would be the result.

Talking about CPUs is already a confusing subject what with talking about clock speeds, socket type, upgrade ability, which RAM is compatible with which CPU and so on. Why make it even more confusing by eliminating a phrase used to tell the difference between two different architectures.

when dpaanlka and I intend to educate you that macbooks are indeed having two processors, we are not using the two processors or dual processor as the identifier of the machine, just description of the machine... the difference is the former needs to be unique, the latter needs to be descriptive. we agreed that we need to acknowledge the difference between 2 CPU on 1 chip and 2 CPU on 2 chips, but we don't think differentiate by calling them DP and DC is appropriate, thus this thread. is that so difficult to understand?

we know the current definition of DC and DP, we are challenging that. if you use the very thing we are challenging to argue, then your further arguments will be ignored.

Sorry for the sarcastic paragraph above but that is basically the argument that you are using. Of course I would be correct to call an Apple Mac a PC, but the point is people tend not too in order to avoid confusion. A PC is generally accepted as being a computer running Windows on either Intel or AMD hardware. Where as a Mac is a computer running OS X on IBM/Motorola or Intel hardware.

That is why it is important to differentiate between dual core and dual processor.

Mac is the identifier of the groups of Personal Computers(PC) made by Apple Computer, Inc. and since the word Mac is somewhat understood by majority (at least here), it is descriptive enough. but if you would to introduce Mac to a completely Mac newbie, you are not gonna tell him "this is a mac, do you not understand what this is, this is a Mac!".. however, you will tell him "this is a Mac, it's a one of those PCs made by apple, it is the only type of machine that can legally run OS X", etc.
because PC, in description, means personal computer, as you said, and just that. in term of identifier, sure, it could me machines that run Windows, Linux, MS DOS among other OSs

but no one's gonna say you are wrong if you say the mac is also an personal computer.. just like we are saying it shouldn't be wrong to say macbook has two processors.


just so you know, mac does NOT have to run OS X to be an Mac. i can erase my OS X and only install Windows, or Linux, and it's still called a Mac

 

[CanadaRAM]

d, I think you may have a small obsession.

There's no doubt that a dual core chip has two processors (CPUs) in it.

And that a machine with two separately chipped CPUs has in fact two "single core" CPUs. And Processor is understood to mean either a Central Processing Unit or more commonly, a generic term for a single self-contained chip that has one set of pins.

Hence a Dual Core Processor is 2 CPU cores in one processor chip.

We're talking about the naming convention that you only refer to 'Core' if there are more than one CPU on the silicon inside one chip.

Not daughter card. Not any other configuration. 'Core' has no distinguishing meaning if there is only one of them. It's like saying that I am a single twin, when I don't in fact have a twin sibling. The word twin implies the special case that there are two siblings born at the same time. Saying that there is a Core implies more than one CPU on the wafer. Which is not the case on single CPU processor systems, no matter how many processor chips it contains.

You can debate semantics all you like, but it comes down to the usage that is understood by the user group. The industry calls multiple CPUs within a single chip that fits in a single socket, a multiple Core processor, and when there is a single CPU on the chip, no matter how many individual chips are installed in the machine or on daughter cards, they are referred to as processors and the word Core is never used. (as it was never, ever used on 9600's or G4s)

Here's some analogies: If I put duallies on the back of my 2 wheel drive pickup, then technically it is a 4 wheel drive vehicle because there are 4 wheels on the driving axle. But 4 wheel drive is understood to mean 4 driving wheels on two axles at opposing ends of the vehicle, so while it would be defensible on a technicality, I would be using the term incorrectly.

A horse is a quadraped. A human is a biped. Two humans walking together are not a quadraped even though they do have four feet.

Two transit busses are not the same as one double-decker bus. We don't call a regular bus a single-layer double decker. Double-decker is a term used to differentiate a bus with two floors on chassis.

 

[Cromulent]

Have you ignored mine? What about where I said "why don't they come up with a different name that doesn't suggest other systems with two processors somehow do not have two cores." They do, after all, have two cores.

That is correct as I have already stated in a previous post a better name for a dual processor system might be something like independent dual core system or the like. Unfortunately though I am not in a position to put this into effect.

Frankly I don't understand what you don't understand. All the systems in question have two processors and two cores. "Dual core" is a bad name to call two processors on a single die, because all two processor systems have two cores. What about that don't you get?

I understand completely. The point is that just because something is true does not necessarily mean that it is correct to use a different term.

I really think calling them dual core, when every other two-processor system also has dual cores, is more confusing than clarifying.

I disagree.

Because the phrase itself is confusing. It leaves the impression that only the systems specifically labeled as "dual core" have two cores, when in reality, every system with two processors has dual cores, regardless of how the chips interface with each other.

I do not think it does. A processor is single core. Saying dual processor means dual cores by default. I do not see the possible reason for confusion using these two naming conventions.

Yes, but "Mac" can in no way be confused with "PC" - all Mac OS and Windows computers are "PCs" - but only computers running Mac OS are Macs. However, in our examples, every system has both two processors and two cores. Completely different, because "core" and "processor" go together. If you have two cores, you have to have two processors, and visa-versa. They cannot be separated.

Not necessarily I am running Windows on my Mac Pro. Does that mean it is no longer a Mac when I boot into Windows? No it does not. My analogy still holds.

 

[dpaanlka]

d, I think you may have a small obsession.

When is this ever not the case?

There's no doubt that a dual core chip has two processors (CPUs) in it.

Super!

Not daughter card. Not any other configuration. 'Core' has no distinguishing meaning if there is only one of them. It's like saying that I am a single twin, when I don't in fact have a twin sibling. The word twin implies the special case that there are two siblings born at the same time. Saying that there is a Core implies more than one CPU on the wafer. Which is not the case on single CPU processor systems, no matter how many processor chips it contains.

Excellent... so why should people who say their dual core systems have two processors be corrected as if wrong? That is what I am not understanding. By your definition, "dual core" is merely a term for a specific arrangement of two processors - which is acceptable to me if people understand that "dual core" does not mean there is only one processor, but rather a very specific arrangement of two processors.

My analogy still holds.

No, because you can't call a PC a Mac no matter what. I changed my post to "computers built by Apple" before you posted to address this... probably while you were creating your post.

 

[Cromulent]

when dpaanlka and I intend to educate you that macbooks are indeed having two processors, we are not using the two processors or dual processor as the identifier of the machine, just description of the machine... the difference is the former needs to be unique, the latter needs to be descriptive. we agreed that we need to acknowledge the difference between 2 CPU on 1 chip and 2 CPU on 2 chips, but we don't think differentiate by calling them DP and DC is appropriate, thus this thread. is that so difficult to understand?

Not at all. It is just the fact that your description of the machine is only used by yourselves, just about everyone else uses the identifier as the description as well (in this case dual core).

we know the current definition of DC and DP, we are challenging that

If you know the current definition then I really do not see what their is to challenge. But none the less I'll take you up on that.

From your above statement I take it we are all clear on the definition of both terms and are in complete agreement with what these terms mean (correct me if I am wrong).

You can call the MacBook anything you like, dual core, dual processor, laptop whatever. The point I am making is that there are generally accepted names for certain things and in this instance this is one where the generally accepted term is different from the one you have been using. The fact that you think that term is stupid, unreasonable, marketing is really irrelevant.

I think the reason that people correct you is so that new users (of computers in general especially) start to see the difference between the two architectures through the use of differing terms to describe them. If I was a new user and no one made that distinction obvious to me I would be incredible confused if someone said that actually you only have one chip in your computer for the CPU. I would think that people had been lying to me saying that I had dual processors.

if you use the very thing we are challenging to argue, then your further arguments will be ignored

That is an incredibly bad way to have a debate with someone. I have had many discussions with people were neither side is willing to back down, simply saying 'further arguments will be ignored' just shows that you have nothing of use left to say.

 

[bearbo]

Not at all. It is just the fact that your description of the machine is only used by yourselves, just about everyone else uses the identifier as the description as well (in this case dual core).

we are trying to point out the fact altho it's identified as dual core, it indeed actually have two processors (sure it's cramped in one chip, it still has two processors)

If you know the current definition then I really do not see what their is to challenge. But none the less I'll take you up on that.

i cannot believe you still dont understand... we are trying to say to ppl who claim it's wrong that dual core has 2 processors, are actually wrong.

From your above statement I take it we are all clear on the definition of both terms and are in complete agreement with what these terms mean (correct me if I am wrong).

you are correct

You can call the MacBook anything you like, dual core, dual processor, laptop whatever. The point I am making is that there are generally accepted names for certain things and in this instance this is one where the generally accepted term is different from the one you have been using. The fact that you think that term is stupid, unreasonable, marketing is really irrelevant.

we are not saying the generally accepted names are wrong, they are correct if you don't implying anything with them, but if you meant "dual core" doesn't have 2 processors, then you are wrong.

i'm also saying that, as stated above, ppl who think dual core doesn't have two processors, are wrong.

I think the reason that people correct you is so that new users (of computers in general especially) start to see the difference between the two architectures through the use of differing terms to describe them. If I was a new user and no one made that distinction obvious to me I would be incredible confused if someone said that actually you only have one chip in your computer for the CPU. I would think that people had been lying to me saying that I had dual processors.

it's incredibly misleading to tell owner of macbook that they only have one processor when they have two... at least that's the way the term dual core is implying.

That is an incredibly bad way to have a debate with someone. I have had many discussions with people were neither side is willing to back down, simply saying 'further arguments will be ignored' just shows that you have nothing of use left to say.

cutting my sentence by half and taking only half of it eh? now that's a bad way of debating. i am saying if you use the very thing i'm challenging to argue, and not adding ANY thing else, your arguments will be ignored.

 

[Cromulent]

we are trying to point out the fact altho it's identified as dual core, it indeed actually have two processors (sure it's cramped in one chip, it still has two processors)

They do in fact have 2 processors so you would be correct in saying that.

Where you would be wrong was if you called it a dual processor machine as I have already stated, and seeing as we have already said that we both agree on the definitions of both terms you would know this.

That is the entire point of this thread. I can not argue this point in any other manner. It always comes back to this point.

 

[dpaanlka]

They do in fact have 2 processors so you would be correct in saying that.

Where you would be wrong was if you called it a dual processor machine as I have already stated, and seeing as we have already said that we both agree on the definitions of both terms you would know this.

That is the entire point of this thread. I can not argue this point in any other manner. It always comes back to this point.

So, saying a Mac Pro has four processors is fine, but not "quad" processors? Is that the finality of all this?

Four vs. Quad?
Two vs. Dual?

 

[Cromulent]

So, saying a Mac Pro has four processors is fine, but not "quad" processors? Is that the finality of all this?

Four vs. Quad?
Two vs. Dual?

I would call the Mac Pro a dual processor dual core machine. 2 processors each with 2 cores = 4 cores split over two chips.

 

[bearbo]

I would call the Mac Pro a dual processor dual core machine. 2 processors each with 2 cores = 4 cores split over two chips.

so would you say mac pro has two processors or four processors? because obviously, if you have gone to elementary school, four does not equal to two

 

[Cromulent]

so would you say mac pro has two processors or four processors? because obviously, if you have gone to elementary school, four does not equal to two

4 cores split over two processors. Seeing as a core is equivalent to a processor it comes out as 4. Hence the dual processor dual core statement.

 

[dpaanlka]

4 cores split over two processors. Seeing as a core is equivalent to a processor it comes out as 4. Hence the dual processor dual core statement.

So, in conclusion, it has four processors. Four cores split between two dies. Not two processors.

"Dual core, dual die" is a better description.

 

[Cromulent]

So, in conclusion, it has four processors. Four cores split between two dies. Not two processors.

"Dual core, dual die" is a better description.

That would satisfy me as a description, yes. The only real reason that such a distinction has to be made between a core and a processor is if a core is refered to as a processor, what do you call the superstructure of a dual core chip. A processor? Well, no you can't as the two cores are called a processor. A CPU, maybe still not particularly clear as a CPU is often refered to as a processor itself.

Anyway I think that just about sums it up . Nice to meet someone as stubborn as myself every now and again .

 

[gnasher729]

Well, since you didn't read the thread, I'll give you a short summary: We all seem to agree there are two actual processors inside all these dual core Macs. I'm not really understanding why "dual core" even exists - as two processors soldered together on a single board has existed long before the term "dual core" was coined, and it was always called "dual processor" - even back then.

The debate going on now is whether or not you can say "two processors" - which I think you should be able to, since there are two processors.

Since you didn't read my post before complaining, I'll try to explain it again: There is no generally accepted definition of "processor". Insisting that there is one doesn't make it so. When shown the same computer, some will say that it has two processors, some will say it has one processor. You can claim that your definition is "the" right one as long as you like, that doesn't change the fact that other people use other definitions. And insisting on a terminology that isn't well defined and globally accepted is only going to create confusion and pointless shouting matches.

 

[dpaanlka]

Since you didn't read my post before complaining

You know, this thread has come a long long way since that post, so I'm assuming you didn't read past that either. Besides everybody here seems to agree what a "processor" is.

 

[Zwhaler]

If you are talking to people who don't know jack about computers and you feel that they would be far more impressed by you saying four "processors" rather than four "cores" just say four processors if it will make you feel better

But technically, the Mac Pro has 4 cores within 2 processors. Because inside the computer, there are two actually processors, and within those processors are two cores. Its like having a car with a V6, you don't call it a "six engine" car, because it only has a single engine with six pistons (the pistons coorespond to the cores). Some people have high-performance go karts with multiple engines, and that is like saying you have a dual processor computer (like in the mac pro) rather than saying quad processor, when in reality it is dual core dual processor.

Don't worry though, in the future there will be single processor, 50 core computers

 

[dpaanlka]

But technically, the Mac Pro has 4 cores within 2 processors. Because inside the computer, there are two actually processors, and within those processors are two cores.

That's already been proven false many many times in this thread. Please read the entire thread.

Its like having a car with a V6, you don't call it a "six engine" car, because it only has a single engine with six pistons (the pistons coorespond to the cores). Some people have high-performance go karts with multiple engines, and that is like saying you have a dual processor computer (like in the mac pro) rather than saying quad processor, when in reality it is dual core dual processor.

No, it's not like that at all.

 

[RacerX]

Interesting discussion here...

It is funny, when Macs first started out, you would have systems with a CPU (like the 68000, 68020 or 68030) and in some cases an FPU (like the 68881 or 68882). There was a lot of confusion when Motorola released the 68040 because the FPU was moved onto the same die with the CPU. And what was even more odd was the fact that they could turn off the FPU within the chip (which was the 68LC040).

One of the aspects of this change was the fact that software the required an FPU would warn you that it didn't see either the 68881 or 68882 co-processor when run on 68040 systems. Some software would work fine after the warning while other software wouldn't.

So, where did this whole dual core thing come from? It came from IBM.

IBM's POWER series was designed for their high end workstations and servers running Unix. By the end of the 90's they were selling workstations with 2, 4 or 8 processors (either the PowerPC 604e or the POWER3 series) to get the performance they wanted. And when they started designing their new 64 bit processor, they decided the put two processors on the same die within a single chip. This was the POWER4 chip.

Part of the key to this idea can actually be traced back to Cray, who realized that to design his supercomputers to be as fast as possible, he needed to shorten the distance the information had to travel. Many people thought that the round designs of Crays were for stylistic reasons, when infact it was to shorten the distance between components.

This same philosophy has been behind much of what we see in processor design today. By putting both the CPU and the FPU on the same die, the distance between them is nearly eliminated, making faster systems and taking less space and resources. By moving part of the memory onto the die (L1 cache) key instructions can be kept almost at the processor (rather than having to retrieve it from main memory). In the case of the later 604e series systems, L2 was given a faster dedicated bus and the G3 and G4 improved on that idea even further. Finally people moved L2 memory right into the chip itself (eliminating the need for a special bus between the L2 cache and the processor).

IBM took this whole idea to the next level with it's 400 series PowerPC processors which had things like a USB controller built into the chip itself... they were basically computers on a chip.

When IBM thought that they might have problems moving their 32 bit based clients (who were using 604e and POWER3 series based systems) to the POWER4 and beyond, they decided to build a transitional chip... based on a single core of the POWER4, but that could execute both 32 bit and 64 bit instructions. The original G5 was a modified single core version of the POWER4.

Back to the question of the thread, a lot of this has to do with how processes are executed on a system... a processor is, after all, the thing that executes the processes of applications.

In the days of the 9500MP, 9600MP and the Daystar multiprocessor systems, System 7 wasn't able to see more than one processor. Daystar wrote some software (which Apple licensed for using in System 7 and later) to allow applications to address the additional processor (or processors in the case of some Daystar systems that had up to four processors). But if apps didn't know that the processors were there or weren't written to take advantage of them, you only got the performance of a single processor system.

Mac OS X changed this... but not by much. Applications still need to be written to take advantage of multiple processors. If they aren't, then they will be executing all of their processes on a single processor. The advantage of Mac OS X is that the system can decide what app executes on what processor. An app that uses a lot of a CPU may get a processor to itself while other (less intensive) apps use another one.

Oddly enough, Adobe's Premiere 6.5 for Mac OS X was only able to use a single processor where as Final Cut Pro could use more than one. This was (in my opinion) Adobe's way of crippling the app to sell their PC Preferred campaign from back then.

Where am I going with all this? Basically, software hasn't changed.

If you have an application that can only execute on one processor, you are effectively no better off with two cores than you would be with one... because the cores are processors. And Mac OS X will allocate both cores in the same way that it would if they were two physically separate chips.

So where is the advantage? We're back to the distance issue... and by having all the processors in a single chip along with large amounts of cache all communicating at the same clock speed as the processors themselves makes multi-processor aware apps significantly faster.

Remember, the primary limitation in computing is the speed of light. There is nothing you can do to go faster than the speed of light, so the obvious solution (as Cray pointed out years ago) is to shorten the distance.

Multi-core chips are multiple processors connected with an incredibly fast bus with almost no distance between them. But from a software perspective, each core is just a processor.