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Are three cores better than two?
Barbarian writes "That's the question that Tom's Hardware asked. They took a dual-cpu motherboard and stuck both a single and a dual core Opteron on the board, for a total of three cores. Does it work? Well, yes, when it's not crashing. It does raise the possibility of tri-core processors whilst we are waiting for the next die shrink."
Pages are loading pretty slow, here's the conclusion for those who don't want to wait:
As you could see, the fact that we used two rather different Opterons for putting together the triple core system had an impact on the benchmark results that was hard to predict. Performance depends on the level of a program's thread-optimization, but we also had a hard time with some particular benchmarks. Some did not work at all (AutoGK w/ DivX or Xvid, Pinnacle Studio 9 Plus). For others, performance was worse than that offered by a dual-core Opteron 275 configuration (such as with memory benchmarks, ScienceMark, WinRAR file compression and Windows Media Encoder). However, the majority of software we used was able to scale well thanks to the third core (which was the case with Cinebench 2003, PovRay 3.7, Cinema 4D R9 and 3DS Max 7).
MrRogers(2)
The XBox uses a P3/celeron hybrid, you mean the XBox360. But the three cores of the 360 are mentioned in the article.
First of all, they used Windows XP SP2. Why the fuck would you do that in a multicore test. Use an OS that can handle that many cores properly. XP definatly can't. Not bashing windows either. I mean if you are going to use a windows OS at least use 2003 server. And why just test one OS? Also, the triple core title is completely misleading. The AMD arch for multicore processors is much more than just two cores stuck in a single incasing (ala Intel's design). It's much more advanced and just sticking a 2nd cpu into a multicore setup is not analagous to adding another core to the tight multicore setup. It's adding a whole 'nother cpu.
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Why not setup one core heavily interger optimized, and one floating point? That way you can run the FP apps like rockets, and the interger apps like lightning w/o comprimizing on either. Rather than have a long chain in the pipeline you could have paralell paths, and once an instruction is set down one path, the CPU could take the next and see if it can stick it down another path.
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No, you might as well go all the way: http://www.iwill.net/product_2.asp?p_id=90&sp=Y
Symmetrical multiprocessing refers to the equality of each CPU in terms of running jobs. Each core has equal opportunity to schedule and execute a thread. The fact that the individual CPUs are different has nothing to do with it.
But thanks for playing the Demonstrate Your Ignorance Of Terminology game.
Opteron systems aren't SMP. They're NUMA.
In theory, the ability to run to chips of different speeds was there even in the Athlon MP, as it had independant busses from the morthbridge. In practice, it didn't work very well, either.
steve
Oh, you're not stuck, you're just unable to let go of the onion rings.
Actually a/symmetric refers to the hardware in the system, not how the OS runs. You can implement a Master/Slave kernel just as easily on an Asymmetric systems as a Symetric one. The basic idea behind SMP is that you have N identical CPUs connected to a common memory controller, and they all have equal access to main memory. Asymetric is where you have either a NUMA machine with each CPU having its own RAM, or a cluster of machines with a backbone fabric, or something similar where talking to some regions of RAM/IO are cheaper than talking to other regions.
It's not that rewarding because the memory bandwidth and low-latency local memory must increase as well to be able to feed the computations. In fact, I will guess that even at a massive 25.6 GB/s bandwidth on the PS3, a properly architected game will still be bus-bound.
So, in the short term parallelization will take the form of tasks that are compute-heavy and don't need to be sync'ed. Cool particles, or cloth sims, or asset streaming and decompression. Then it's a diminishing returns game as we move from 4 procs to n.
You don't need special software to take advantage of muliple CPUs. All you need to more threads or processes. Certainly for servers this is not a problem for the desktop if you run multiple programs at once multiple CPUs can be used. However most users don't stress even one CPU. Unless you are running a game or rendering video. One thing, I looked at iTunes and found it had 11 threads active. THese were all running on one litle 1.25Ghz G4 processor (without stressing it in the least) So even if I had bought a quad core power Mac, iTunes would surely have used those four cres but I'd see absolutly zero increase in speed. If the single CPU is not at 100% utilization then adding another CPU means that both will run below 50%. OK, so my point is you need BOTH an applacation sweet that has multiple threads/processes AND a big enough job to get done such that the CPU is used past 100% Many uses just don't do this kind of work Only if you play games or create digital content.
Obviously not. From TFA's first page:
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I've been using a Sun E450 with 3 processors for the better part of 5-6 years. Not sure how well it "balances" the load, but when I use TOP it seems to indicate that Solaris is in fact spreading the load appropriately.
He meant hypercube. He wasn't referring to the physical structure of the chip. The cores are frequently arranged (logically) in a hypercube structure, and interconnects are placed where the edges are in the resulting graph. It works quite well, actually. However, these are VERY expensive systems.
The work for a video game can be divided quite a bit. The issue is more that game programmers are used to programming for single CPU processors because 99.9% of computers and consoles had only a single processor - hopefully the XBox 360 & PS2 will change that.
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Sun has released its T1 chip which boasts 8 cores capable of running 4 threads each. As mentioned on slashdot before, its considered a "green" chip becuase it only requires aprox. 70 watts to run (think lightbulb). Sun has a 2U server with this chip, 32 Gigs of ram and 2 SAS drives all for around (or under) $30k. This is complete redesigning my future datacenter planning. Oh yeah. I forgot to mention, This is shipping now and runs only Solaris 10.