Article:
  Apple's High-Water Mark?
Subject:   Cell's PPE is not at all related to the POWER5
Date:   2006-03-27 21:24:23
From:   riskin
I'm not sure where you came up with the statement that the Cell’s PPE is derived from the POWER 5, but in your own link to Anandtech's article on the cell it states "The PPE is a new core unlike any other PowerPC core made by IBM."


It is a very simple, in-order execution processor with a high clock speed to help offset this in-order design. If it is derivative of any IBM design, it is certainly not the POWER 5.


For a detailed analysis of the Cell, I recommend Jon "Hannibal" Stokes' articles here:


Part 1: http://arstechnica.com/articles/paedia/cpu/cell-1.ars


Part 2: http://arstechnica.com/articles/paedia/cpu/cell-2.ars



As mentioned by a poster above me, you seem to be downplaying the difficulty of extracting performance from the Cell for general computing tasks. Yes, the Cell is a media processing beast and has the potential to be a boon in certain computing tasks. However, the majority of code run on personal computers (you know, the ones that Toshiba, Sony, and Apple all make) does not benefit at all from the additional SIMD processing elements in the Cell. So the only thing you're left with for day to day computing (web browsing, word processing, chat, email, book keeping, and so on) is the relatively weak processing power provided by the Cell's PPE. Granted, if you wanted to encode one of your DVDs into a format suitable for your Video iPod, the Cell would whip through it like a bulldozer through cheese.


Quite simply, the Cell is not in any way well suited to general purpose computing at all. Yes, it may suffice in that role and under certain conditions, but every application of it deals with processing massive amounts of data: games, scientific and high performance computing (supercomputing), media processing, and other workstation (aka task-specific machines) environments. I'd love to see a Cell co-processor paired with a general purpose CPU. We see such pairings of powerful, highly parallel media processors with general purpose CPUs all the time. They're called video cards. They are great at what they do, but if you tried to run an OS on a graphics chip you’d kill yourself.


I think you're pretty far off the mark to suggest that Apple has to fear the Cell being adopted by computer makers as a central CPU. In fact, I think your argument that Cell-based devices such as a Linux powered PS3 will do anything to impact Apple or Microsoft on the desktop. The Cell is just not designed to be a general purpose CPU, and attempting to argue otherwise misses the point.


However, you are correct that the PS3 is an excellent vehicle to expose a large number of people to Linux.

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  • Cell's PPE is not at all related to the POWER5
    2006-03-30 17:39:12  pquam [View]

    If by general purpose computing, you mean email, internet, the office suite, etc., then all you need is a PIII and some fast drives. In other words, the excitement about general purpose computing is dead. The only way to make general purpose computing fun anymore is to pack it into something that weighs 6 oz., or give it unbelievable performance per watt.

    At up to 4ghz with absolutely phenomenal I/O, Cell is more than fast enough for this stuff; all of the overhead generated by techniques to try to feed the processor (like out-of-order processing) continuously actually slowed down the P4 and its sucessors, in my opinion. The consensus in the processor design community is that chips had become unnecessarily complicated with these techniques, and that they didn't pay enough attention to I/O. Cell was specifically designed to remedy that.

    Cell is a specialized processor, and its specialty is in what consumers care most about: multimedia. This was also Apple's specialty until recently, which is what I assume led to this article's focus on Apple. Cell has over 200 fully programmable gigaflops, which is like 30 times more than your average processor these days (or about 3 times more than a quad G5). Cell is a consumer electronics dream.


  • Cell's PPE is not at all related to the POWER5
    2006-03-29 13:08:11  AdrienLamothe [View]

    Digital media is where the commercial computing market is heading, it is where most of the action will be. Apple has a core group of customers, who have been with Apple a long time, who use Macs primarily for digital photos, sound and film. Cell is optimized for digital media and computational work; this makes it very attractive to people who work with digital media. You can connect the dots from here.

    Regarding the Cell processor's roots in the Power5 architecture, perhaps it is best to quote an article in the IBM Journal of Research and Development, authored by the Cell architects. You can find this article at:

    http://www.research.ibm.com/journal/rd/494/kahle.html

    Three sentences stand out:

    1. "Indications were that a completely new architecture can easily require ten years to develop, especially if one includes the time required for software development. Hence, the Power Architecture* was used as the basis for Cell."

    2. "By the end of 2000 an architectural concept had been agreed on that combined the 64-bit Power Architecture* [4] with memory flow control and “synergistic” processors in order to provide the required computational density and power efficiency."

    3. "The Broadband Processor Architecture extends the 64-bit Power Architecture with cooperative offload processors (“synergistic processors”), with the direct memory access (DMA) and synchronization mechanisms to communicate with them (“memory flow control”), and with enhancements for real-time management."

    Regarding the difficulty of extracting Cell processor performance from a programming perspective, a large effort has been underway to provide developers with the necessary programming tools. Intel has been doing the same thing for their Core Duo architecture. A muti-core, multi-processing environment is about to become the new norm; those who refuse to adapt will suffer the same fate as others in the past who didn't change with the technology. If you want to develop relatively simple applications, then you will likely be able to continue using your current programming model. If you program on top of engines such as Apache, then you also won't likely need to worry about it; the Apache developers will port to the new environment and you won't have to deal with it.

    Cheers,

    Adrien