dual GHz is not really 2 GHZ?

Discussion in 'Hardware Rumors' started by nerveosu, Jan 18, 2002.

  1. nerveosu macrumors member

    Joined:
    Sep 17, 2001
    #1
    Just asking....

    I was under the impression the dual G4s are not really twice as fast as a single cpu. Maybe 1.5x but not 2x.

    I guess it depends what you are doing and with what software... i do know it does help a lot in 3d rendering

    -bill


    Am i wrong?
     
  2. Falleron macrumors 68000

    Falleron

    Joined:
    Nov 22, 2001
    Location:
    UK
    #2
    Its not. However, apple might use a naming scheme like AMD has.
     
  3. colocolo macrumors 6502

    Joined:
    Jan 17, 2002
    Location:
    Santiago, Chile
    #3
    It's not twice as fast. It depends in eah program in the number of threads that run simultaneously and in the data dependency between them.

    As an example (not the best one, i know), if you have two stoves, you can cook the potatoes and the chicken at the same time, but it won't help you get only the chicken ready any faster.
     
  4. Ensign Paris macrumors 68000

    Ensign Paris

    Joined:
    Nov 4, 2001
    Location:
    Europe
    #4
    AMD

    I hope apple used AMD style names, it would get them more cred!

    Guy
     
  5. sparkleytone macrumors 68020

    sparkleytone

    Joined:
    Oct 28, 2001
    Location:
    Greensboro, NC
    #5
    based upon my understanding, as long as you are in OS X it CAN be twice as fast. this is not really the important point tho. i need bus speed.
     
  6. colocolo macrumors 6502

    Joined:
    Jan 17, 2002
    Location:
    Santiago, Chile
    #6
    The big advantage of OS X is that it distributes processor loads very well. This means, you will never get a processor running at 100% of its capacity while the other is idle, at least when running multiple applications or when running a single application with multiple threads.

    If you run a single process with a single thread, you will get the same performance from a single or a 32-processor system, regardless of the OS. This is because in that case, the CPU needs to receive the result of the execution of the last line of code before attempting the next one, so there's pretty much nothing you can do in that case.
     
  7. networkman macrumors regular

    Joined:
    Jan 1, 2002
    Location:
    california, usa
    #7
    so a dual 1 ghz is not as fast as a 2 ghz in every single scenario, but one thing is for sure...

    the dual 1 ghz, if it comes out, will sell to high end users

    if i had the money, i would want one too but i am not a graphics person but my wife seems to do fine with her freelance clients using her ibook

    but for the "big" jobs and the color critical stuff, a dual 1 ghz with a 24" inch color calibrated high end crt is what a big studio house would most likely use

    what a monster that machine would be if it is for real
     
  8. krossfyter macrumors 601

    krossfyter

    Joined:
    Jan 13, 2002
    Location:
    secret city
    #8
    If the new ghz come out...how much will they be marked for?
     
  9. ThlayliTheFierce macrumors regular

    Joined:
    Jul 31, 2001
    Location:
    San Luis Obispo, CA
    #9
    Probably the same price as the 800 dualie now.
     
  10. MrMacMan macrumors 604

    MrMacMan

    Joined:
    Jul 4, 2001
    Location:
    1 Block away from NYC.
    #10
    no way apple needs more money, if they need more money they raise prices, not lower them, why would you do that. Oh just to tell ya 300 posts baby!!
    :D:D :D :D :D

    He he he he he
     
  11. krossfyter macrumors 601

    krossfyter

    Joined:
    Jan 13, 2002
    Location:
    secret city
  12. krossfyter macrumors 601

    krossfyter

    Joined:
    Jan 13, 2002
    Location:
    secret city
    #12
    okay call me stupid but im dont understand the dualie thing.

    i mean i know it has 2 sets of proccesors....however does that mean speed on any task that requires speed is actually doubled? or is it only for certain tasks? whats the deal here. im sure this has been explained more on this forum but hell there is sure a lot of techies going around talking to techies and i kinda get lost with the number thing.....im an artist so bare with me.


    :D
     
  13. anshelm macrumors member

    Joined:
    Jan 17, 2002
    #13
    More analogies, anyone? :)

    Imagine going to an amusement park with a stunning rollar coaster ride that was getting rave reviews. You stand in the queue line, get on the coaster, zip through, have fun, and come out exhausted. The amusement park realizes that the roller coaster often times gets so overcrowded that they could open a duplicate roller coaster to get the extras, and keep people pouring in. So they do. Larger numbers of people can be handled at once, yet it still takes just as long for a roller coaster ride to happen. So it can do more because it has a larger "width" (that refers to how many whatevers you can cram through whatever it is you are measuring).

    A dual G4 is quite similiar to the amusement park. Now, there are certain things that can't be run simultaneously (say you want to add five to a number, and then multiply the result by 6... you can't do the multiply and add at the same time because the computer won't know what to multiply by 6 until the add is done!) due to data dependencies (the add and multiply example) and other things like that. The "people" in the "roller coaster" (processor) are the equivalent of "threads". Not quite exactly, but pretty close.

    Now, to get the full picture, add a guy at the front of the queue lines that will send you to one line or the other to keep the lines as close to the same length as possible. This will keep the roller coasters running will closer to equal sized loads, so that nobody has to wait as long for the coaster to be ready again.

    That's what MacOS X does. And, from what I understand, it does a very good job at it. This allows a dual processor to get much higher performance (in some areas equal to almost 150% - sorry about the "200%", that was a typo!) then a single processor system (in certain areas... that comment was not meant to mean in all areas... sorry about that!). You won't get a 2GHz system from having two 1GHz processors, you'll get something better: higher FLOPS (which is what is the REAL indication of power... my Athlon 1.2 running, in Linux, a no-hands-held number crunching routine I wrote came up with... 400 MEGAflops! Now the 11.8 Gigaflops advertised by Apple is not with MacOS X running, but I imagine it is still much better then my Athlon's rating), but that inof itself is another thread.

    (Windows NT (and XP, which is just NT 5.1 with an ugly face and name change on the outside) fills up one processor to full capacity and then goes on to the next processor. Which really hurts dual processor systems that choose to foolishly use Windows instead of *nix.)

    Anyway, I hope my rant was helpful on the performance issue.
     
  14. krossfyter macrumors 601

    krossfyter

    Joined:
    Jan 13, 2002
    Location:
    secret city
  15. pc_convert? macrumors regular

    Joined:
    Jan 18, 2002
    Location:
    UK
    #15
    Dual CPU's is not equivalent to twice the speed of a single CPU. There are various overheads comunicating between the processors which performance gain. Anything upto 1.5 times the performance is a good estimate, but it depends on the software.
     

Share This Page