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Dual-Core Processors

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Today most of the talk seems to be revolving around Dual-Core Processors. I read awhile back that having two separate Processors was better than having a Dual-Core Processor is this true? The fact that cooling two separate CPU's would be easier than trying to keep a handle on a Dual-Core would make it more advantageous for two separate CPU's also the cost for two separate CPU's would possibly be cheaper. I would like a little clarification on what all the hoopla is all about.

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Reviews of the new dual core Intel CPU's are all over the net as of yesterday.  Check them out to answer your questions.

201441[/snapback]

I have read the reviews. Maybe I wasn't clear enough so here's a clear cut question: Intel's Dual-Core Processor is $1,000.00 two Opteron 246 CPU's are $600.00 why would I want to spend more for a Processor that is hotter and possibly not as efficient as running two separate CPU's?

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Reviews of the new dual core Intel CPU's are all over the net as of yesterday.  Check them out to answer your questions.

201441[/snapback]

I have read the reviews. Maybe I wasn't clear enough so here's a clear cut question: Intel's Dual-Core Processor is $1,000.00 two Opteron 246 CPU's are $600.00 why would I want to spend more for a Processor that is hotter and possibly not as efficient as running two separate CPU's?

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you wouldnt. Intel is sorely lacking in the dual cpu market (even with their new dual core cpu), as the cpu's (core's) have to fight for shared memory access. Amd's technique of giving each cpu its own memory controller and dedicated memory bandwidth (via hyper transport) is far superior.

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So, we have two different issues.

Dual-core Intel: Dual core Intel chips should operate EXACTLY the same as dual-processor Intel systems. (So this dual-core 3.2GHz chip on an 800MHz bus should operate absolutely the same as two 3.2GHz Xeons on an 800MHz bus.) This is because all of Intel's dual-processor systems have worked in essentially the same manner as this dual-core chip. One processor bus, with two processors sharing it. Intel's implementation of dual-core is taking two complete processor cores, and slapping them together. (In the first implementation, it will be on the same piece of silicon, on later chips, it will be two physically separate cores just packed on the same package.)

Dual-core AMD: AMD has a completely different situation going. AMD's dual processor systems have had a major advantage over Intel in that each processor has its own dedicated bandwidth to the chipset. In the case of Opteron's, each processor even has its own independent memory controller, so each processor gets its own full speed connection to main memory. (This does have a downfall that if one processor wants to access something that's in memory linked through the other processor, it does tie up the other processor a little bit.) The big downfall of AMD's dual-core situation is that it will remove this major AMD advantage. (Go find reviews.) AMD's dual-core will have two processor cores on the die, but only one memory controller, and one link to the chipset. This is actually being done for the sake of compatibility, so that existing chipsets and motherboards won't need to be replumbed. The other option would have been to make a new socket that is really a socket plumbed for two processors. AMD wants it simple, by enabling dual-core in just a BIOS upgrade.

In short: dual-core removes AMD's current advantage in dual processor technology. Time will show if that will be enough of an leveller to let Intel catch up. (Although this new dual-core proc by Intel crushes AMD on multi-thread and SSE-enhanced media apps, AMD leads almost everywhere else.)

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Today most of the talk seems to be revolving around Dual-Core Processors. I read awhile back that having two separate Processors was better than having a Dual-Core Processor is this true? The fact that cooling two separate CPU's would be easier than trying to keep a handle on a Dual-Core would make it more advantageous for two separate CPU's also the cost for two separate CPU's would possibly be cheaper. I would like a little clarification on what all the hoopla is all about.

I think it's likely that one dual core outputs less heat than two individual cores, although not much less. I don't think heat is any greater of an issue that it already was, anyways.

The "hoopla" is not quite warranted yet, in my opinion--it's going to take years for single thread programs to evolve into multi-threaded applications that can take advantage of dual core stuff, and a lot of programs will never be optimized for dual core. Since the best way to do a lot of programs is with a single thread (KISS being the main reason, IMO), there's a lot of programs that will see a performance decrease going to a dual core chip. Some will see great increases simply because they're heavily threaded to begin with. Multitasking will almost always be better, but how many casual users run Flash, Photoshop, and VS.NET 2003 while surfing the net and ripping a CD? Not many that I know of. I've never had a problem with an Athlon 64's multitasking capabilities, so it really begs the question--why upgrade?

I know the application I'm currently writing will take enourmous advantage of dual cores (if I can get dual hyperthreaded cores, that'd be even better), but I have a feeling I'm the exception to the rule.

Edited by MisterDuck

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So you are saying that there is no difference in performance having two separate CPU's versus a Dual-Core CPU running at the same speed, the only reason I'm asking is I read that there is an advantage in performance running two separate CPU's versus a Dual-Core.

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So you are saying that there is no difference in performance having two separate CPU's versus a Dual-Core CPU running at the same speed, the only reason I'm asking is I read that there is an advantage in performance running two separate CPU's versus a Dual-Core.

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If you're talking to me, yes--there's a difference between two CPUs and a dual core chip, although assuming memory bandwidth is ample, probably not much. From a programatic perspective, however, both are pretty much the same thing.

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Reviews of the new dual core Intel CPU's are all over the net as of yesterday.  Check them out to answer your questions.

201441[/snapback]

I have read the reviews. Maybe I wasn't clear enough so here's a clear cut question: Intel's Dual-Core Processor is $1,000.00 two Opteron 246 CPU's are $600.00 why would I want to spend more for a Processor that is hotter and possibly not as efficient as running two separate CPU's?

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No, the one dual core CPU (840 Extreme Edition) you picked is $1000. How much does the single core P4 EE cost? $1000. Looks like a pretty good deal to me. Getting a second core at a slightly lower clock speed for the same price.

Reported 8xx series prices:

840 (3.2GHz): $528

830 (3.0GHz): $314

820 (2.8GHz): $240

Compare those prices while including a motherboard and RAM to Opteron prices, and the advantage is pretty clearly in Intel's corner.

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Dual core vs Dual cpu in AMD.

The most important difference is that a dual-core AMD will have two 128-bit memory busses, while a dual-core setup will have just one 128-bit bus. Also Shared L3 cache can make a difference.

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In short: dual-core removes AMD's current advantage in dual processor technology.  Time will show if that will be enough of an leveller to let Intel catch up.  (Although this new dual-core proc by Intel crushes AMD on multi-thread and SSE-enhanced media apps, AMD leads almost everywhere else.)

201449[/snapback]

What is you conclusion based on? I am yet to see any dual core AMD processor reviews.

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In short: dual-core removes AMD's current advantage in dual processor technology.  Time will show if that will be enough of an leveller to let Intel catch up.  (Although this new dual-core proc by Intel crushes AMD on multi-thread and SSE-enhanced media apps, AMD leads almost everywhere else.)

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Eh, why exactly?

As far as I know the performance difference between a s754 A64 and a s939 A64 isn't that big, so there may be a lot of memory bandwidth 'left'.

Also, the advantage only disappears if you replace two single-core CPUs by one dual-core CPU. If you 'just' upgrade the two (or more) single-core CPUs to dual-core CPUs, the advantage remains.

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The market niches for dual procs would seem to be:

1) Replacing single-core CPUs in single CPU mobos. For Intel, this is their answer to the lack of the P4 architecture to ramp up higher in Ghz because of thermal problems. For AMD, this is their answer to Intel's Hyperthreading.

2) Replacing single-core CPUs in a server motherboard. Positioned as an inexpensive "upgrade" to existing server hardware, and a way to lower the price/performance of the next generation of servers. Addresses a slightly differing market problem than 1) above, as server applications tend to be more multi-threaded anyway, and so will have a more linear performance gain than the above use. I would expect prices for dual-core chips targeted at servers (Xeon, Opteron) to maintain some cost premium over those for single-CPU boards, not because they will cost more to produce, but because they will have a greater impact on the workload targeted. And, of course, there is that traditional server premium anyway :-( .

Lastly, you also need to factor the cost of the motherboard into the mix - dual proc motherboards have always been more expensive, sometimes double or more if "server" features are added.

Anyway, just my $.02...

Future Shock

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In short: dual-core removes AMD's current advantage in dual processor technology.  Time will show if that will be enough of an leveller to let Intel catch up.  (Although this new dual-core proc by Intel crushes AMD on multi-thread and SSE-enhanced media apps, AMD leads almost everywhere else.)

201449[/snapback]

What is you conclusion based on? I am yet to see any dual core AMD processor reviews.

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here, and here. (Bring a translator for the second one.)

As for why dual-core is slower in some instances than single-core? Really just because at least to start, dual-core (for Intel,) will be slower in GHz than the fastest single-core chips. For example, the dual core sample that's been going around is 3.2GHz, whereas Intel's fastest single-core is up to 3.8GHz. So for programs that aren't multi-threaded, you're going to lose performance, because the app will act like you're on a single 3.2GHz chip.

Finally, as for my comment above, it's based on single-socket boards, yes. AMD keeps (even, in some sense gains) ground in dual-socket boards, because while yes, the two cores would be sharing a single memory bus, each socket would have it's own. Whereas on an Intel dual-socket, dual-core system, all four cores would share a single memory bus. (And that 'dual socket' system would appear to the OS as a 8-way system because of HyperThreading, holy cow!)

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In short: dual-core removes AMD's current advantage in dual processor technology.  Time will show if that will be enough of an leveller to let Intel catch up.  (Although this new dual-core proc by Intel crushes AMD on multi-thread and SSE-enhanced media apps, AMD leads almost everywhere else.)

201449[/snapback]

What is you conclusion based on? I am yet to see any dual core AMD processor reviews.

201466[/snapback]

We don't need to see reviews to know that's the way the architecure was designed. While Opterons each have a dedicated hypertransport, dual core CPU's will have both cores sharing the same hypertransport. What is unknown right now is how much that will affect performance for dual core AMD chips, but we can say with pretty good certainty that at best it should be slightly slower than a dual Opteron setup. This isn't an issue with Intel dual core, since even their SMP systems already shared the same bus, so putting two cores in the same socket brings no fundamental changes to how the cores communicate with the rest of the system compared to 2 seperate CPU's.

Really just because at least to start, dual-core (for Intel,) will be slower in GHz than the fastest single-core chips. For example, the dual core sample that's been going around is 3.2GHz, whereas Intel's fastest single-core is up to 3.8GHz.

That's a rather lame comparison, and not really accurate either. A 3.2GHz P4 will not be any faster than a 3.2GHz dual core P4 at anything including completely single threaded applications. That's the comparison everyone else is referring to. You don't compare a 3.8GHz chip to a 3.2GHz of the same family, as obviously we all know which one will be faster. They aren't even in the same price bracket. Intel has priced dual core CPU's with a pretty low increase over the same clocked single core CPU's. The estimated price for the 3.2GHz dual core P4 is less than the cost of a single 3.6GHz P4 660, so that tells you where Intel thinks it falls on the performance ladder. Comparing current clock speeds also implies you don't see Intel increasing the clock speed of their dual core CPU's. I would wager they will. Though I don't really see how they can get that much farther since the 3.8GHz seems to be about the limit for even a single core CPU.

For anyone looking at building a dual Xeon server in the future, the question almost has to be, "why?", at this point. These dual core CPU's look like they will be a whole lot cheaper to build than a traditional SMP system while performing practically indentically, and with Intel's newest generation of PCI-E boards, traditional SMP boards don't even have the advantage of higher bandwidth expansion slots anymore, while still costing a whole lot more than highend single CPU boards. Of course dual core dual Xeons would be quite a nice server.

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We don't need to see reviews to know that's the way the architecure was designed. While Opterons each have a dedicated hypertransport, dual core CPU's will have both cores sharing the same hypertransport. What is unknown right now is how much that will affect performance for dual core AMD chips, but we can say with pretty good certainty that at best it should be slightly slower than a dual Opteron setup. This isn't an issue with Intel dual core, since even their SMP systems already shared the same bus, so putting two cores in the same socket brings no fundamental changes to how the cores communicate with the rest of the system compared to 2 seperate CPU's.

uhmm? Hypertransport on Dual-Core Amd CPUs will have lot of bandwith, so that it should not have a big influence on the performance.

Anyway... Intels actual 'Dual-Core' technic is actually technically the same as on Dual-Xeon Boards. Except that you don't have to have 2 sockets.

So IMHO this is not really a 'big' change in technology (or technology leadersip).

on AMDs side, this is going to be slightly different. They did not only put 2 cores together on one die, no, they do share L2 Cache, what has several advantages. On AMDs side there's also NUMA.

The two AMD Opteron/Athlon64 on one die AFAIR communicate together through an HT-Link. But not the external, for sure. NUMA runs also trough this.

If you look at 'older' NUMA Benchmarks with 4 Opterons, you can see a Memory Bandwith increase from about 7000MB/s to >20000MB/s!

that was with 'external' HT-Link... with internal the distance is lower, thus allowing decreased latencies. And... it doesn't stress the 'external' HT-Link.

Then there's the power consumption, too.

Pentium EX with Dualcore 3.2GhZ (incl. HT) has got a TDP of 130Watt, meaning a Top of 172 1/3 Watt. Woohoo... new world record ;)

i suppose it could be even higher.

if the Pentium EX consists of 2 'low power' 82Watt TDP 3.2 Pentium 4 (HT), then it could reach >200Watt...

AMDs Opteron Dualcore CPUs will be about 100Watt max.

AMDs Athlon64 Dualcore CPUs will be lower. Winchester are currently at 40Watt max, putting two of them together would result in approx. 75Watt...

and , AFAIR, there will be a 50Watt Version for Opteron Dualcore, too.

On the really 'big' machines (like crays 'red storm' project) power consumption is a major criteria.

cya

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there's a lot of programs that will see a performance decrease going to a dual core chip.

Why?

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Because a program that is single threaded cannot make use of a second core. Sometimes it's just not possible to split a workload easily between two threads--having multiple threads in a sequential process simply doesn't make sense. Even more daunting is that you're using someone else's API, in which case you're at the mercy of how they programmed it. Rewriting existing APIs from Microsoft, for example, is going to be a fantastically huge project--and in many instances, I guarantee they'll just leave it single-threaded because of the difficulties of porting some given "task" to a multi-threaded architecture.

So, if you had a dual core Prescott running at 3.2 GHz and a single core Prescott running at 3.6 GHz, the one running at 3.6 will beat out the 3.2 when running a single threaded program.

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there's a lot of programs that will see a performance decrease going to a dual core chip.

Why?

201487[/snapback]

So, if you had a dual core Prescott running at 3.2 GHz and a single core Prescott running at 3.6 GHz, the one running at 3.6 will beat out the 3.2 when running a single threaded program.

201704[/snapback]

You didn't say slower-clocked dual-core CPU, you said dual-core CPU.

Don't change things you didn't even mention.

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You didn't say slower-clocked dual-core CPU, you said dual-core CPU.

Don't change things you didn't even mention.

201709[/snapback]

I wasn't trying to change anything, just explaining myself--sorry, next time I'll be more specific.

Since most dual-cores are probably going to be clocked less than their single core equivalents (especially on the Intel side of the equation), I figured that was obvious.

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You didn't say slower-clocked dual-core CPU, you said dual-core CPU.

Don't change things you didn't even mention.

201709[/snapback]

I wasn't trying to change anything, just explaining myself--sorry, next time I'll be more specific.

Since most dual-cores are probably going to be clocked less than their single core equivalents (especially on the Intel side of the equation), I figured that was obvious.

201718[/snapback]

That'd depend on the definition of equivalent. Same price? Same clockspeed? Something else?

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I like the "same price" definition of equivalence. In which case the dual core = lower clocked argument holds. However, comparisons of dual core vs. single core at the same clockspeed can provide useful technical insights, irrespective of relative price or value.

Practically nothing will see a slowdown when going from single core to dual cores at the same clockspeed, and even single threaded apps will benefit if something else (e.g. virus scanning, P2P downloading) is going on in the background. But when cost comes into it, you really need to compare equivalently priced platforms to get a fair and useful comparison.

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IBM used dual core in the POWER4. So there is some information on what to expect. The Mac OS already uses dual core (and Tiger will further that, and some apps like Safari web browser are very efficient at using both cpus).

"A dual-core chip is more effective than a single-core chip on problems that stress the computational resources of the chip, more than the front-side bus bandwidth. Because the 970FX has a very fast, efficient front-side bus, most Mac applications will favor the dual-core configuration."

eWeek: IBM Readies Dual-Core PowerPC

Hurricane, the third-generation Enterprise X-Architecture chipset, is the heart of X3, providing the x366 with an integrated processor and memory controller that significantly reduces memory latency, improving response times and overall system performance for customers. The XA-64e chipset was specifically designed for xSeries by a cross-platform architectural team who has expertise from IBM's mainframe heritage.

Some key advantages available exclusively from the Hurricane chipset include:

Significant improvement in price-performance versus previous generation x365.

Substantial improvement in processor-to-memory latency reduction critical for commercial enterprise workloads.

Virtual XceL4v Dynamic Server Cache delivering intelligent caching with memory latency so low that a physical L4 cache is not necessary.

Embedded Dynamic Random Access Memory (DRAM) with an integrated snoop filter and remote directory.

Three scalability ports, each operating at 6.4 GB/s, among the fastest in the industry.

Leading in Transaction Processing Performance. 

IBM 64-bit Intel X3 Xeon

Also, IBM Unveils Second-Generation AMD Opteron-Based Server With Support for Dual-Core Processor Specification

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IBM used dual core in the POWER4. So there is some information on what to expect. The Mac OS already uses dual core (and Tiger will further that, and some apps like Safari web browser are very efficient at using both cpus).

201769[/snapback]

Some POWER processors even have 4 cores in one package. And the Mac OS already uses multithreading heavily, which takes advantage of dual processors. Rumors are that the next PowerPC 970 chip will be dual-core, and that the next Apple G5 will use them; but those are still rumors. (I think IBM accidentally posted a page about the 970MP, but then withdrew it, so the dual-core PPC is still officially just a rumor.)

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Hi

I'm more interested in Dual Core because it makes it far, far cheaper to build a 4 way system. When Dual Core Xeons and Opterons come out it'll be possible to pack four cores in a PC chassis on a affordable (ish) motherboard. No more crappy 400MHz FSBs and massive, massive price premiums for 4 way systems! The way Intels pricing seems to be heading, it'll be possible to build a 4 way system for only slightly more than a 2 way system costs today. Now that's worth getting excited about.

Dave

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