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The death of CPU scaling: From one core to many — and why we’re still stuck By Joel Hruska on February 1, 2012 at 2:31 pm
The multi-core swerve
For the past seven years, Intel and AMD have emphasized multi-core CPUs as the answer to scaling system performance, but there are multiple reasons to think the trend towards rising core counts is largely over. First and foremost, there’s the fact that adding more CPU cores never results in perfect scaling. In any parallelized program, performance is ultimately limited by the amount of serial code (code that can only be executed on one processor). This is known as Amdahl’s law. Other factors, such as the difficulty of maintaining concurrency across a large number of cores, also limit the practical scaling of multi-core solutions.
Amdahl`s Law
AMD’s Bulldozer is a further example of how bolting more cores together can result in a slower end product. Bulldozer was designed to share logic and caches in order to reduce die size and allow for more cores per processor, but the chip’s power consumption badly limits its clock speed while slow caches hamstring instructions per cycle (IPC). Even if Bulldozer had been a significantly better chip, it wouldn’t change the long-term trend towards diminishing marginal returns. The more cores per die, the lower the chip’s overall clock speed. This leaves the CPU ever more reliant on parallelism to extract acceptable performance. AMD isn’t the only company to run into this problem. Oracle’s new T4 processor is the first Niagara-class chip to focus on improving single-thread performance rather than pushing up the total number of threads per CPU.
The difficulty of software optimization is a further reason why adding more CPU cores doesn’t help much. Game developers have made progress in using multi-core systems, but the rate of advance has been slow. Games like Rage and Battlefield 3 — two high-profile titles that use multiple cores — both utilized new engines designed from the ground-up with multi-core scaling as a primary goal.
The bottom line is that its been easier for Intel and AMD to add cores than it is for software to take advantage of them. Seven years after the multi-core era began, it’s already morphing into something different.
kad softver ne može da ih iskoristi, tj. programeri neće da ga napišu kako treba.
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Da ste vi zivi i zdravi Intel 6 ore je postao potreban pre godinu dana. Ne neophodan ali vidljivo bolji u sve vise aplikacija. Sada kupiti 4 core nije bas pametno ako zelis neki maksimum. Kada smo vec kod CPU stigla mi je Arctic MX-4 pasta trenutno najcenjenija i najtrazenija za graficke karte i procesore. Kosta 800din i ima u EMMI. Mislim ima sada pa za godinu dana, zadnjih 4-5 meseca je cekam. Rok trajanja je duzi nego ostale, 8 god tako da se vise isplati nego NT-H1 koja je 2-3. Iskoristite sada situaciju ako imate neko djubre cesto menjate. Ja na godinu dana stavim novu.
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