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Difference between dual dual-core and quad core?

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May 11, 2007 7:12:28 AM

can anybody tell me what's the difference between a dual dual-core (fake quad core) and a real quad core?

With fake quad core I mean like 2 dual cores forged together

More about : difference dual dual core quad core

May 11, 2007 8:00:19 AM

What is the difference when looking how it works?
May 14, 2007 9:17:45 AM

are there any benches of this?
dual-dual vs quad?
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May 14, 2007 12:08:29 PM

Quote:
are there any benches of this?
dual-dual vs quad?

I don't believe there are any benches because no true quad exists yet
May 14, 2007 12:34:15 PM

isnt QX6800 and the Q6600 true quad cores? as apose to AMD's 2x2 FX71?
May 14, 2007 12:36:32 PM

I thought they were both just two dual cores stuck together, i could be wrong though........
May 14, 2007 12:44:53 PM

I think its kinda ridiculous to say what is true (quad) or not.

4 cores is 4 cores. Even a Quad SLI is based upon 2 cards with 2 GPUs, which makes it a SLI quad system.

The only thing that maybe of different is the architecture of the CPU since that affects how well or not how well it performs.
May 14, 2007 12:47:35 PM

Would it be possible to make an MCM with an on-chip interconnect between the cores?

This way it would be possible to sidestep the latencies when cores communicate with eachother using the FSB. A compromise between the usual MCM and single die multicore.
May 14, 2007 1:07:44 PM

umm, i'm only a first year EE so most of that went right over my head...but i think AMD is shooting for something that doesn't have to use the FSB to communicate.
May 14, 2007 3:46:59 PM

Quote:
can anybody tell me what's the difference between a dual dual-core (fake quad core) and a real quad core?

With fake quad core I mean like 2 dual cores forged together

There is no thing like fake quad core, but there is a MCM(multi-chip module) quad core and there would be a native(single chip module) quad core.
Right now(and for quite some time), there are only Intel quad core CPUs which are a MCM of two native dual core chips. Sometimes this year AMD would bring a quad core too, which will be a native quadcore. AMD used to spread marketing FUD and bash Intel about their MCM approach, but internally they want and consider to produce a MCM latter.
Both approaches have advantage and disadvantage. The native approach has better connectivity(significantly lower latency and higher bandwidth) between the cores. This is very important for three or four threaded applications when the cores are communicating very often and are needing low latency communication. The negative side of this approach is the low production yields, thus their price is much higher. The chips on the MCM are connected via slower bus(in Intel's case it is the FSB which is shared for RAM and I/O), but the production yields are much higher.
Optimized quad threaded applications performance will scale more linear with the native approach, but right now there are almost no quad threaded applications.
May 14, 2007 5:38:29 PM

Thank you very much for that explenation!!!
May 14, 2007 7:33:13 PM

Quote:
can anybody tell me what's the difference between a dual dual-core (fake quad core) and a real quad core?


Really, nothing as far as you are concerned. I think even Intel would admit that their current solution is a stop-gap until they integrate everything on one die. But this situation is very similar to the one we were in way back when there was the option on having cache memory on die vs in a separate silicon die but wire bonded on to the same substrate vs cahe on the motherboard.

(Back then there was a speed difference because you were taking the fastest bus on the chip and leading it across the motherboard, when otherwise it could stay on chip. In this situation, while these are fast interconnects, they are fast interconnects that had to go out anyway, and the inter-cpu traffic isn't all that much in most practical circumstances.)

Back then, there was discussion of which approach was best, but, with the benefit of hindsight it is clear that it was best to regard this a purely an internal issue. What you got and what you paid for it are the things, and the marketing nonsense of 'we've got a better arch, nah, nah, na, nah, na' isn't in the short term as important as who wants your business more, and so who offers a discount to get your business, because that often counterbalances internal production cost issues.

In the longer term, you have to look at the roadmap/plans for the platform, but you were going to do that anyway, right?

So, if you are trying to decide which to buy, you should compare what you get for what amount of money (performance, compatability with stuff you've got already, like motherboards and RAM, and the other stuff like 'future proofing'). You shouldn't 'add extra points' for one approach or the other, the production costs are already baked into the price you get charged, and you don't need to add it in again.

from verndewd
Quote:
well we cannot derive much from comparison of AMD and Intel. Honestly I dont know if it matters either way. You may think that 4 cores on one die will communicate faster between cores ,But if the architecture is not as efficient it doesnt matter if its native quad or 2 dies.


The trouble is that a benchmark compares everything in the system and given that we know that Intel and AMD give different results, you know that'll you get different results even if the 'real/false' causes no difference. But, as I argue above, just look at, say, benchies for the whole system and the cost of the whole system and ignore how its done. The biggest bang per buck is the biggest bang per buck. End of story.

Quote:
Seperate dies can induce latencies with longer pathways unless its designed around that and through put doesnt rely on cross die communication which if not done right can also cause latencies.


While that's also correct, part of that is at the level of how the OS/Application ditributes the workload around and whether it ever has to move stuff around between cores. So, the CPU manufacturer can't really control that.

Here, the AMD arch, with its Hypertransport bus is 'better'. In essence, HT is probably going to work as well as it works (unless the HT clock changes) whether it is working between chips on one slice of silicon, two on one module, or four spread around a motherboard. OTOH, there is little evidence that the Intel approach of using the bus to memory to communicate between cores has a problem at today's CPU clock speeds and memory speeds. Sometime, if CPU speeds and numbers keep going up and memory bus speeds don't go up at least as fast, it will become a bottleneck, but it hasn't happened yet.

But, you can regard the AMD approach of being more elegant and having better ability to scale, but that really isn't worth much until the Intel approach shows limitations.

from brad81987
Quote:
umm, i'm only a first year EE so most of that went right over my head...but i think AMD is shooting for something that doesn't have to use the FSB to communicate.


Yes, well that's true, But Intel are using the FSB because that's what Intel always does (until some future arch comes along) and AMD are using the HT bus, because that's what AMD always does. So, the comment is correct as it stands, but it just doesn't come from 'true' or 'false' dual cores, just the difference in approach that the two organisations have in their architectures at this point.
May 14, 2007 7:39:09 PM

Quote:
isnt QX6800 and the Q6600 true quad cores? as apose to AMD's 2x2 FX71?


The QX6800, QX6700, and Q6600 are all quad cores, but they are two dual cores in the same package.

AMD's 4x4 system uses FX-70, FX-72, and FX-74 processors in their system, all are dual cores. This form of making a quad core system is inherently going to be more expensive and use more electricity, due to even higher overhead then two dual cores in the same package, and the need for a second processor.
May 14, 2007 7:55:22 PM

I'm not going to buy a quad core but I have to do a paper on it and I didn't know this difference.
Thank you all for replying! this has helped me a great deal!

tom's hardware forum is has an overload of information and very much activity!

I wrote a special thanks to this site ^^
!