Multiple Cores?

AbsoluteZeroAbsoluteZero The new film by Quentin KoopantinoRegistered User regular
So I'm looking into getting a new computer or possibly building one. However, one thing I don't exactly understand is the benefits of a multi-core processor. For instance, what is the advantage of a dual core 2GHz processor vs. a single core 2GHz processor? Why should I shell out any extra cash for a multiple core machine?

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  • VulpineVulpine Registered User regular
    edited January 2008
    Generally it's difficult to compare clock speed between processors, especially with different (micro)architectures. A 3Ghz Pentium 4 may look impressive on paper, but a 2Ghz Core 2 Duo will outperform it quite happily.

    With this in mind, having multiple cores is like having multiple processors, only on the one single processor die instead of having multiple physical processors to install. This means that calls to the processor cache by each core is significantly faster, as they no longer need to traverse the system bus. With less distance to travel, the signals degrade less as well, so faster transfer rates to cache are possible.

    Furthermore, SMP-aware applications can happily balance their threads between cores for simultaneous execution.

    Of course, as with multiple physical CPUs, adding cores does not increase the clock speed. (If I have to read one more eBay auction claiming "dual core 2 Ghz = 4 Ghz!!!", I will kill the lot of them.) However, as multicore CPUs are becoming decidedly common, expect just about every new game to benefit as developers code for them. SMP stalwarts like Photoshop should also see a tasty speed increase.

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  • AbsoluteZeroAbsoluteZero The new film by Quentin Koopantino Registered User regular
    edited January 2008
    That makes it seem a lot more like a worthy investment. Thanks for the info!

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  • EggyToastEggyToast Registered User regular
    edited January 2008
    Besides a single program, modern OSs will balance the load across the cores/chips for multiple programs. So even if, say, a video encoding app doesn't use multiple cores, it can happily max out Core 1 (at like 99% usage) while still giving you an entire core for everything else you're doing. Essentially, it's like having a CPU meter that maxes out at 200% (or 400%) instead of 100%.

    I've found that even in situations where you wouldn't *think* it would help, your computer is rarely running only 1 application. For instance, you boot up your Windows PC, and within the first 2-4 minutes your antivirus loads up, your spyware monitor loads up, your Windows Update thing scans, etc. On a single-core/CPU computer, each of those ends up on the same chip, which is why a computer would be so slow when you hit the desktop for the first few minutes.

    With a multicore/cpu computer, those processes essentially take half the time, and if you load up Firefox right away, it can hop on a core with low current usage and load that much more quickly.

    With single-threaded applications, you likely won't see much difference by having multicore, within than single application. This is currently a big deal with high-end audio applications that run instruments and effects and are often single threaded. They end up maxing out the CPU they're on and running out of juice, without the user really noticing any problems (making it harder to diagnose). On the other hand, applications like that can use almost an entire core w/o other applications messing with them.

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  • SmudgeSmudge Registered User
    edited January 2008
    Yeah, on my current single core machine, if am doing something like unraring a huge file and trying to watch a divx encoded movie at the same time, the movie playback will go to SHIT on me or even stop until that file is done.

    A friend of mine with a dual core often has one monitor happily playing a divx movie while he is doing whatever he wants on the other monitor with no effect on the movie playback. It is very slick.

    I suspect I will be drooling once my wifes new MB, CPU, and ram arrive. But she has a lot more need for multitasking right now.

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  • AbsoluteZeroAbsoluteZero The new film by Quentin Koopantino Registered User regular
    edited January 2008
    That is excellent because I do a fair deal of work in Photoshop and also various video editing and dvd authoring programs, and that always makes my machine grind to a halt so I can't even, say, check my email while I've got VOB files encoding.

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  • steeefsteeef Registered User regular
    edited January 2008
    Just to add to the list of benefits, I'm running two copies (one for each core) of [email protected] on my dual-core machine, which means cancer will be cured in half the time. Right?

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  • TxdoHawkTxdoHawk Registered User
    edited January 2008
    steeef wrote: »
    Just to add to the list of benefits, I'm running two copies (one for each core) of [email protected] on my dual-core machine, which means cancer will be cured in half the time. Right?

    Doesn't [email protected] have multi-core support? I could have sworn it did, but I could be wrong.

    To the OP, while dual-core is definitely the way to go now, don't automatically assume that more cores will always be significantly better. It will depend entirely on what you are using the computer for, and the specific software running. For example, most modern games are only just beginning to truly take advantage of dual-core processors, while quad-core doesn't seem to offer much in the way of gaming performance benefits just yet.

    Like everything else in new technology, there is always a price-to-performance sweet spot based on need, and it'd be a good idea to figure out what exactly that is for the kind of PC you want to own. Going too far ahead of the curve gets expensive fast.

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  • steeefsteeef Registered User regular
    edited January 2008
    TxdoHawk wrote: »
    steeef wrote: »
    Just to add to the list of benefits, I'm running two copies (one for each core) of [email protected] on my dual-core machine, which means cancer will be cured in half the time. Right?

    Doesn't [email protected] have multi-core support? I could have sworn it did, but I could be wrong.
    It's certainly possible, but when I was setting stuff up, it was recommended that I use two separate FAH console clients.

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  • GihgehlsGihgehls Registered User regular
    edited January 2008
    I've got a quad core system. I can be encoding a DVD to xvid at roughly 60fps, encoding two xvids to .flv at about 30fps each, and working with about 12 tabs open in Firefox, all with no noticeable system lag whatsoever. Definitely worth it.

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  • ShineyBlueShoesShineyBlueShoes Registered User
    edited February 2008
    Well it's clearly worth it if you're stepping up in performance and getting another core but what if you're getting a dual core processor that's the exact same speed? Worth it still if it's from a 3700+ to a X2 3600+?

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  • GihgehlsGihgehls Registered User regular
    edited February 2008
    Absolutely worth it 100%. Single core computers are quickly becoming a thing of the past, and like Eggy said, essentially your available CPU would go up to 200%.

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  • DarmakDarmak RAGE vympyvvhyc vyctyvyRegistered User regular
    edited February 2008
    My roommate just built himself a new computer a few days ago and got one of AMD's new Phenom processors. It's supposedly the first true quad core CPU on the market. I don't know how true this is, but I do know that it's a bad motherfucking machine.

    Also, I hear the new ATI Radeon HD 3870 X2 has two GPUs. I don't know if they're dual core or just two GPUs on the same board, but this is still the first I've ever heard of such a thing. Anyone know if this would be worth checking out?

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  • ZxerolZxerol HOW MANY POUNDS IS CAT POOP Registered User regular
    edited February 2008
    Darmak wrote: »
    Also, I hear the new ATI Radeon HD 3870 X2 has two GPUs. I don't know if they're dual core or just two GPUs on the same board, but this is still the first I've ever heard of such a thing. Anyone know if this would be worth checking out?

    It's two GPUs on one board. It's nothing new, actually. Nvidia did something similar with the 79x0 GX2 (although those were really two 79x0 boards sandwiched on top of each other). Much earlier, ATI had the Rage Fury MAXX cards, which sported two Rage 128 GPUs. Let's not forgot the Voodoo 4/5 series, the top dog being the infamous Voodoo 5 6000 with four VSA-100s on one PCB, and required an external power source to juice it up. You thought video card technology is crazy today...

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  • ShineyBlueShoesShineyBlueShoes Registered User
    edited February 2008
    Darmak wrote: »
    My roommate just built himself a new computer a few days ago and got one of AMD's new Phenom processors. It's supposedly the first true quad core CPU on the market. I don't know how true this is, but I do know that it's a bad motherfucking machine.

    Well it's true from the standpoint that the Phenoms have four independent cores on the die while the Q's are two Core Duo's on a single die.

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  • victor_c26victor_c26 Registered User regular
    edited February 2008
    Yeah, that's the major difference with the Phenoms and the Qs. The Phenoms cores can talk to one another and send data and code to one another. The Qs have to talk through the bus Northbridge in order for one pair of cores to talk to the other pair.

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  • LaCabraLaCabra Registered User regular
    edited February 2008
    So is a Phenom worth it then?

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  • victor_c26victor_c26 Registered User regular
    edited February 2008
    Well, only if you already have an AM2 machine.

    They're good for what they are, but they still lag behind Intel's Qs.

    The architecture itself though has potential. Only time will tell.

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  • LaCabraLaCabra Registered User regular
    edited February 2008
    Interestin'.

    What's the best quad core you can get right now? And also what's the second-best.

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  • victor_c26victor_c26 Registered User regular
    edited February 2008
    I think the best bang for the buck is currently the Q6600 (Anything higher, and the price multiplies absurdly), also Intel is set to release the Yorkfield die Q series line pretty soon. So the Q6600 will be replaced with a Yorkfield equivalent.

    As for the Phenoms, I think the best bang for the buck is the 9500. As the next step only gives you an extra 100Mhz for $34.

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  • ShineyBlueShoesShineyBlueShoes Registered User
    edited February 2008
    From what I've read if you actually go with the whole "spider" set up it's supposed to work pretty well in crossfire with two 3870's and it's not much more then a Q6600 with a single 8800GT I believe. And even though some non 7 series mobos can be flashed to the AM2+ socket I've read that it's really hit and miss whether it works right or not. Even if it does though they still are supposed to hold the Phenoms back a bit.

    So much a matter of taste though. Like I know the Intel/Nvidia combo's performing much better right now for not that much more but I have this bad taste in my mouth with them for whatever reason.

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  • Nakatomi2010Nakatomi2010 Registered User
    edited February 2008
    This example may seem a bit extreme, it is true...

    My single core Athlon 64 used to take about 4 days to rip 8 to 10 DVD into XviD files....

    My Q6700 did the same project in 8 hours....

    Brief history of multi-core technology....

    AMD releases the Athlon 64x2 inot the market and says "Look we're first into the dual core processor market, look at how blazingly fast our processor are!"
    opty_dual.gif
    Notice the cross bar and how it allows the two cores to communicate properly

    Intel says "Oh shit, we need something to compete" and out pops the Pentium Ds, essentially two Pentium 4 duck taped together on a single chip....
    pentiumd_architecture.jpg
    The important thing to see here is the arrows between the two cores and the front side bus, this is essentially a 3 way stop, they cannot all talk to each other at the same time, so either the two cores can talk, or one core and the front side bus, or the other core and the bus, but not all three together. VERY inefficient design.

    Intel's R&D department then had to act fast and came up with the Core 2 Duo design which mimicked AMDs efficient design...
    intel-core2duo-diagram-440x370.jpg
    In this picture the L2 cache is acting like AMDs crossbar, which allows for seemless discussion between the cores and the system bus, this allows both cores to access the same information within the cache and be far more efficient than the indepent cache system the x2's have...

    Intel then decided "Well you know, we could duct tape two of thee together and be the first into the Quad Core market way before AMD and get ourselves known for it early...
    imageview.php?image=6250
    Could not for the life of my find a better picture :( But as you can see its the same design as a Pentium D , what makes it so powerful though is the efficiency of the cache layout wihtin the cores that allows the two cores to crunch their numbers and report back to the bus.... Kinda like having four two split into two rooms where each team can share the same library of information and sends a runner out to the teacher each time they get their answer, but much faster...

    AMD Meanwhile bought ATi to get at their chipsets so AMD could compete against Intel's own chipset design and stop worrying about selling their concepts to chipset manufacturers, instead AMD can now create their own chipsets and prove their optimum configurations. This move slowed them down a bit, but overall AMD has better footing against Intel now. AMD however said "Look, they did the same thing again, that tape doesn't fool anyone....
    PhenomTripleCore.jpg
    I know the picture represents a triple core, but it also applies to a quad core design...
    Basically, we can see AMD learned from Intel's efficient design and added a shared cache level, Intel shared cache is higher so it allows for more number crunching, but AMDs power is in the cross bar which allows for the 4 cores to talk to the RAM and the rest of the system at the same time. If AMD were to increase the L3 cache, in theory the ssytems should pick up significantly more speed.....

    Intel turned around and said "Look AMD our chips are still faster than, *sticks their tongues out*, neener neener neener neener...."
    AMD of course is the brainiac in the corner who typically takes the abuse and just sits there plotting and planning their next triumph...

    The way I see it Intel will do one of two things... They will A: Release their own variant of a true quad core processor so that they can later duct tape two of the together to achieve an octo-core processor or B: Release an Octo-Processor that is four Core 2s on the same die, while AMD will make a true octo-core processor.....

    Also note that Intel's design allows them to increase the number of core on a processor fairly rapidly as they can just keep duct taping Core 2s together, but you then end up at a ceiling of performance as that damned bus will always cause a traffic jam and AMD hypertransport system will allow the spice to flow....

    Edit: Hey, I was right.... http://www.digitimes.com/mobos/a20080201PD211.html
    AMD's 45nm processors are expected to see core frequencies greatly increased, while L3 cache sizes will grow from 2MB to 6MB. Power consumption of the cache will also see a significant drop, noted the sources.

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  • AbsoluteZeroAbsoluteZero The new film by Quentin Koopantino Registered User regular
    edited February 2008
    Octo-core? That is insanity.

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  • DaedalusDaedalus Registered User regular
    edited February 2008
    Octo-core? That is insanity.

    Not nearly as insane as a six megabyte cache. Jesus.

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  • Mr_RoseMr_Rose 83 Blue Ridge Protects the Holy Registered User regular
    edited February 2008
    Of course. Octo-core is not exactly new technology. Octo-core in a consumer-level desktop is new. Cray and friends have been building 256+ core bespoke machines for years. But then they were selling them for tens of millions to people like NASA....

    That said, I'd like to see what kind of crazy shit you could pull using eight cores with 6MB of cache pumping data out to a couple of quad-core GPUs. Might even be able to play Crysis at better than 800x600. :P

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  • ShineyBlueShoesShineyBlueShoes Registered User
    edited February 2008
    Well you know AMD's going to get back on top in both CPU's and GPU's before long. It's just the way the industry goes. I'm just glad they haven't been schlepping over priced awful product on us like Intel and Nvidia have done in the past when they were second. Yea it's not as good but it's still decent value like their stuff has always been.

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  • DarmakDarmak RAGE vympyvvhyc vyctyvyRegistered User regular
    edited February 2008
    Mr_Rose wrote: »
    Might even be able to play Crysis at better than 800x600. :P

    Unpossible! :D

    But seriously though, I'm really excited to see what AMD and Intel both will bring to the table in the future. I have a Core 2 Duo right now because when I built this computer it was the best thing available at the time, and it's still a damned good processor. However I've always been a fan of AMD and I trust that they'll come out on top again and my next computer will feature one of their CPUs.

    Also, my roommate with the Phenom is planning on getting 4 more gigs of RAM, and 3 more 3870's (once the drivers for all that comes out he says). Is this insane? (y/n)

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  • AbsoluteZeroAbsoluteZero The new film by Quentin Koopantino Registered User regular
    edited February 2008
    So here's another question... have the manufacturers pretty much given up on increasing speed, and instead are focusing on duct taping more and more processors together?

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  • ShineyBlueShoesShineyBlueShoes Registered User
    edited February 2008
    It's a touch excessive but if you don't mind having a jet engine in the room and a PSU so powerful it adds $3 to your electric bill per minute you can't beat quadruple goodness.

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  • victor_c26victor_c26 Registered User regular
    edited February 2008
    So here's another question... have the manufacturers pretty much given up on increasing speed, and instead are focusing on duct taping more and more processors together?

    Well, they're trying to do both.

    The goal is still ultimately to make a faster processor, but since this is getting harder and harder to do, adding more processor cores adds that extra kick to make up for it.

    Now if Intel and AMD somehow manage to create an architecture that are both processing speed breakthroughs and multi-core integration wonders, good times will be had by all right after that happens.

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  • Mr_RoseMr_Rose 83 Blue Ridge Protects the Holy Registered User regular
    edited February 2008
    The trouble with that is the stupid legacy x86 architecture everyone is stuck with until someone with both clout and balls decides to change it. Or armageddon happens, whichever. It's been tried in the past with interpreters and stuff, but switching over to a RISC based chip would simplify chip design and speed things up. The thing is the interpretation of x86 code; either you do it and it fails (this is the approach that I mentioned) or you completely switch over to a novel architecture and tell all your previous software to go fuck itself....

    Time was, back in the bad old days of the WinTel pseudo-monopoly, that Microsoft could have just told Intel to redesign its chips, put out a completely new system architecture and everyone would have either loved it or died, computationally speaking of course.

    Nowadays, only Apple has both the system architecture and the (proprietary) hardware stranglehold to switch over to an entirely new CPU architecture almost at will. In fact they already did it once...they just went in the wrong direction for the sake of cheapness.

    Not that RISC lets you make faster chips in terms of clock rates, that's still a fairly hard limit of how much juice you can pump into a piezoelectric crystal; it's just that way back when BBC/Acorn was the third computing platform in the UK, they had a chip that was outperforming a P90, including when running Windows through an interpreter, that had a clock speed of 25 MHz. And, IIRC, it was out at retail before the P90 too. That is, you get way more bang for your buck...as almost every mobile phone manufacturer today will tell you.

    [/rant]

    tl;dr:
    Current system bad because of BC. Scrap BC for new (oooold) way, go fasta.

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  • victor_c26victor_c26 Registered User regular
    edited February 2008
    If both companies do that, we would need a transitional period where motherboards come equipped with both x86_* sockets and *Enter new platform code-base* sockets. Where the OS would use either processor types through some sort of reverse virtualization technique.

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  • DaedalusDaedalus Registered User regular
    edited February 2008
    Don't modern x86 chips just translate all the x86 code into a RISC-like set of instructions and then execute that?

    In fact, I'm pretty sure they've been doing that since the Pentium II.

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