What does DUAL MEAN?!!!

Discussion in 'Mac Basics and Help' started by Ashapalan, Apr 28, 2005.

  1. Ashapalan macrumors 6502a

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    #1
    I know nothing about Dual Processors.

    And im still confused as to whether dual 2GhZ means two processors of 2Ghz each, equalling an overall of 4 ghz, or whether it means two processors of 1 ghz each....
    HELP!
     
  2. 840quadra Moderator

    840quadra

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    #2
    that system has 2 2ghz processors.

    They don't multiply when connected, the system can simply split work between the processors. Some applications will FLY with this. Some programs are not Dual aware, so speed gains are negligible.

    Since Macintosh computers have had Dual processors for years now, most modern programs can take advantage of them.
     
  3. DXoverDY macrumors 6502a

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    Apr 19, 2005
    #3
    correct in that it's 2 processors, each running at 2ghz. You do not get an effective 4ghz.

    A computer runs what are called "threads" or "processes" we'll think of them the same here for simplicity. 2 processors can run 2 threads at the same time. or two applications for example. If 1 program has more than 1 thread then it's possible to get both processors running a seperate thread for 1 program. this means you get 2 processors going on one app. in theory you'd get 4ghz of power.. but in reality it's not as effecient. think of it as the ability to do multiple things on your computer without interuption.
     
  4. Ashapalan thread starter macrumors 6502a

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  5. makisushi macrumors 6502

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    #5
    Dual means 2 processors each running at 2 ghz. It does not mean you get 4ghz though, just two processors running simultaneosly at 2ghz each.

    I am horrible at analogies, so I will give it my best shot:
    Let's you have a hose with one water supply water turned on full and it can shoot the water 20 feet. But this is not just any ordinary hose this hose can expand to double its size. At double its size, one water supply can only shoot the water 10 feet. but if you hook in another water supply it can shoot the water 20 feet at double the capacity.

    With 2 processors, you can crunch double the numbers. Volume, not speed.
    does that make sense?
     
  6. Mechcozmo macrumors 603

    Mechcozmo

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    #6
    It is usually a 40% speed boost if you use dual-processor aware programs, but that can vary. And that test was with G4s, but still should hold for the G5s.
     
  7. Sun Baked macrumors G5

    Sun Baked

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    #7
    Only in the Wintel fantasy world do those numbers stack up like that, but not quite there in the "real" world.

    And don't forget the dual channel DDR memory bus... ;)

    Which grabs memory across two PC2700/PC3200 dimms at the same time, which require pairs of matched dimms be installed.

    Or the dual-link DVI port... :p

    Lot's of duals in the duals.
     
  8. Platform macrumors 68030

    Platform

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    Dec 30, 2004
    #8
    Very correct.....not just Dual-link DVI but Dual Dual-Link DVI on the 6800 :rolleyes:
     
  9. Rod Rod macrumors 68020

    Rod Rod

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    #9
    Yup, but 8.5GB DVD±Rs are double-layer, not dual layer. :)
     
  10. Mechcozmo macrumors 603

    Mechcozmo

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    #10

    But you can have dual double-layer drives. :D
     
  11. raincoat macrumors member

    raincoat

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    #11
    Dual Dual Dual Cores?

    Would one of you enlightened people now explain how the DUAL core will help? i understand that one could run two different operating systems on one chip-what else can they do, will they improve performance? Although i have done a little digging into this, assume that i know nothing please! :confused:
     
  12. mkrishnan Moderator emeritus

    mkrishnan

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    #12
    The concept is very much the same...applications that use threading or some other technique to distribute work among more than one core will be substantially faster. The OS will be faster in general, because multitasking demands (and in a modern OS, there are always more than a dozen processes running doing something or other) will be open to being split up.

    Dual core and dual processor configurations don't really compete, but two big advantages of multi-core processors are that they will probably be a lot cheaper to manufacture than two single-cores, and they will consume less circuit board space and use less power. Disadvantages include the fact that you typically do not have a total replicated system of two sets of inputs and outputs, so if lots of data is going in/out of the CPU, this may act as a bottleneck, I think. I'm not sure about that, though, because I think dual processors are on the same bus.

    Also look here: http://en.wikipedia.org/wiki/Dual_core ... an invaluable and easy-to-use source of information. ;)
     
  13. garybUK Guest

    garybUK

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    Jun 3, 2002
    #13
    Dual core is putting two processor die's in a single package, Pentium 4 Hyperthreading have this and the increase is about 15% - 20% speed increase. They run a lot hotter because there are two lots of cycles running at the same time in the same package. In windows the OS see's a Hyper threading or dual core cpu as two seperate processors hence is only really an improvement to dual aware app's like photoshop, although some games have seen an increase.
     
  14. Nermal Moderator

    Nermal

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    #14
    Technically, yes, you get 4 GHz. In practice, you don't.

    Remember, the GHz rating is just the number of cycles per second. If you had 2 CPUs each cycling 10 times per second, then the total performance of the entire system would be 20 cycles per second.

    However, we tend to talk about MHz and GHz on a per-processor basis, rather than a per-system basis. So, in practice, you don't effectively get double the performance, and we don't refer to two 2 GHz CPUs as 4 GHz.
     
  15. atszyman macrumors 68020

    atszyman

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    #15
    Hyperthreading is NOT dual core. Intel just recently announced Dual core chips while hyperthreading has been around for at least 6 months, I think more like a year but I'm too lazy to research. Hyperthreading has 2 instruction pipelines feeding the same CPU core which is why you only see a 15% increase or so, I believe that dual core systems typically see close to a 40% increase on apps that take advantage of it.

    Due to their pushing of clock speed Pentiums have an un-godly long instruction pipeline. In order to keep the pipelines full you have to predict where branch statements will go otherwise every time you hit a branch you will have to empty the pipeline to figure out where to go which would start to eliminate the benefit. Since you're prediction will sometimes be wrong you will end up doing this anyway which is where the second instruction pipeline comes in handy. Normally the processor will try to handle both pipelines by multiplexing which would give no benefit over a single if branch prediction were perfect. But when it makes a prediction mistake on one pipe, it can simply feed off of the other until the wrong one catches back up yielding the performance increase.

    I hope this makes sense.
     
  16. mkrishnan Moderator emeritus

    mkrishnan

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    #16
    Just a random question for intellectual curiosity ... when Intel made the 486dx/2 and 486dx/4 processors, which had external speeds that matched the single processor speed (25 or 33 MHz, IIRC), but had twice or four times the number of instructions per cycle internally, was this an early example of a dual core processor? If not, how was it different?
     

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