The Consoles and their CPUs

The CPUs at the heart of these two consoles are very different in architecture approach, despite sharing some common parts.  The Xbox 360’s CPU, codenamed Xenon, takes a general purpose approach to microprocessor design and implements three general purpose PowerPC cores, meaning they can execute any type of code and will do it relatively well.

The PlayStation 3’s CPU, the Cell processor, pairs a general purpose PowerPC Processing Element (PPE, very similar to one core from Xenon) with 7 working Synergistic Processing Elements (SPEs) that are more specialized hardware designed to execute certain types of code. 

So the comparison between Xenon and Cell really boils down to a comparison between a general purpose microprocessor, and a hybrid of general purpose and specialized hardware. 

Despite what many have said, there is support for Sony’s approach with Cell.  We have discussed, in great detail, the architecture of the Cell processor already but there is industry support for a general purpose + specialized hardware CPU design.  Take note of the following slide from Intel’s Platform 2015 vision for their CPUs by the year 2015:

 

The use of one or two large general purpose cores combined with specialized hardware and multiple other smaller cores is in Intel’s roadmap for the future, despite their harsh criticism of the Cell processor.  The difference is that Cell appears to be far too early for its time.  By 2015 CPUs may be manufactured on as small as a 32nm process, significantly smaller than today’s 90nm process, meaning that a lot more hardware can be packed into the same amount of space.  In going with a very forward-looking design, the Cell processor architects inevitably had to make sacrifices to deal with the fact that the chip they wanted to design is years ahead of its time for use in general computation.

Index Introducing the Xbox 360’s Xenon CPU
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  • Darkon - Friday, June 24, 2005 - link

    #49

    WTF are you talking ?

    The Cell does general-purpose processing although not as good as 360 cpu.


    And Anand I suggest you do some more research on cell
  • Alx - Friday, June 24, 2005 - link

    Someone explain to me how Sony will support 1080p please. If developers make the games run at acceptable framerate at that resolution, most people running them at 720p and 480i will be wasting at least half of PS3's rendering power.

    On the other hand if XBOX360 game devs make their games run just fast enough at 720p, that'll give them far more resources to work with than those poor Sony game devs.
  • Shinei - Friday, June 24, 2005 - link

    That's not necessarily true, #48. The Cell processor doesn't do general-purpose processing, so it can't do decoding on its own--and as far as I know, even pressed DVDs have to be decoded by some kind of processor. (Of course, I know next to nothing about video equipment, so I could be wrong...)
  • arturnow - Friday, June 24, 2005 - link

    Another difference between RSX and G70 is hardware video decoder - PureVideo, i'm sure RSX doesn't need that which saves transistors count
  • freebst - Friday, June 24, 2005 - link

    Actually, in response to 31 there is no 1080p 60 frame/sec signal. the only HD signals are 1080 30p, 24p, 60i, 720 60p, 30p, 24p.
  • BenSkywalker - Friday, June 24, 2005 - link

    Why the support for lower resolutions? I'm a bit confused by this- I can't see why anyone who isn't a fanatic loyalist wouldn't want to see the highest resolution possible supported by the consoles. The XBox(current) supports 1080i and despite the extreme rarity in which it is used- it IS used. Supporting 1080p x2 may seem like overkill, but think of the possibilities in terms of turn based RPGs or strategy games(particularly turn based) where 60FPS is very far removed from required.

    The most disappointing thing about the new generation of consoles is MS flipping its customers off in terms of backwards compatability. Even Nintendo came around this gen and MS comes up with some half done emulation that works on some of 'the best selling' games. Also, with their dropping production of the original XB already it appears they still have an enormous amount to learn about the console market(check out sales of the original PS after the launch of the PS2 for an example).
  • Warder45 - Friday, June 24, 2005 - link

    errr #31 not 37
  • Warder45 - Friday, June 24, 2005 - link

    #37 is right on the money. There is a good chance that there will be no HDTV that can accept a 1080p signal by the time the PS3 comes out.

    It seems less like Sony future proofing the PS3 and more like Sony saying we have bigger balls then MS. Not to say MS is exempt from doing the same.
  • IamTHEsnake - Friday, June 24, 2005 - link

    Excellent article Anand and crew.

    Thank you for the very informative read.
  • masher - Friday, June 24, 2005 - link

    > "Collision detection is a big part of what is commonly
    > referred to as “game physics.” ..."

    Sorry, collision detection is computational geometry, not physics.

    > "However it is possible to structure collision detection for
    > execution on the SPEs, but it would require a different
    > approach to the collision detection algorithms... "

    Again, untrue. You walk the tree on the PPE, whereas you do the actual intersection tests on the SPs. The SPs are also ideally suited to calculating the positions of each object (read: real physics) and updating the tree accordingly.

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