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What Makes Apple's Power Mac G5 Processor So Hot

Posted by Hemos on from the learn-the-basics dept.

An anonymous reader writes "58 million transistors can drive a lot of power. Apparently, Apple appreciated the choices IBM processor architects made when designing the 970 family. This article provides the 64-bit architecture big picture for the 970 family (A.K.A. the Power Mac G5) and the critical issues in IBM's 64-bit POWER designs, covering 32-bit compatibility, power management, and processor bus design."

6 of 313 comments (clear)

  1. 64 bit integers by Xpilot · · Score: 4, Insightful
    From the article:
    ...64-bit processors also accelerate complex mathematical calculations through their ability to perform calculations directly on 64-bit numbers...
    Don't they mean 64-bit integers? Since floating point registers in most modern CPU's are 64-bit wide already.

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  2. Re:anyone else noticed how COOL the AMD-64 chips r by Noah+Adler · · Score: 5, Insightful

    I was able to hold my hand on the heatsink and it was barely warm.

    It could be because there's inadequate conduction between the CPU core and the heatsink. Check the temperature monitors to make sure it's actually as cool as you hope it to be. It could be that just most of the heat is staying in on the CPU, which would be a bad thing. Hopefully you've already checked this though.

  3. Nitpicking... by Tristandh · · Score: 5, Insightful

    Capable of addressing an astronomical 18 billion GB, or 18 exabytes, of memory,

    I know the first 2 digits are 1 and 8, but 2^64 bytes is still 'only' 16 exabytes...

  4. Re:Increased Pointer size by Eccles · · Score: 4, Insightful

    In most meaningful, sizeable programs, pointers aren't a significant chunk of memory usage. (And for small programs, it doesn't matter.) I would think most modern apps consume most of their memory storing images, which aren't affected by the 32->64 change.

    Also, 64-bit pointers allow you to go from a max of 4GB of RAM to 16 billion GB, so the assumption is memory prices will keep dropping and you'll have much more than twice as much RAM on your 64-bit system anyway.

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    Ooh, a sarcasm detector. Oh, that's a real useful invention.
  5. Re:Heat Problem Back Ground by the_2nd_coming · · Score: 5, Insightful

    umm, what heat problem? the 9 fans and liquid cooling are in their respective models to solve a SOUND problem. not a heat problem. but then if you bothered looking up statistics on the G5 you would not be able to bash the mac would you?

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    I am the Alpha and the Omega-3
  6. Re:What makes it so hot (abridged) by John+Whitley · · Score: 5, Insightful
    Wow. Artful and elegant rebalancing of engineering tradeoffs for very diferent markets reduced to a knee-jerk oversimplification in one fell swoop. And it got a +5 Insightful for that, too boot. Here are some reasons why the "stripped it down a bit so we don't cut into our own market" statement is ridiculous:
    1. If selling POWER series chips to Apple was going to undermine IBM's server business, IBM would have a hell of a lot more to worry about from the plain 'ol x86 market.
    2. IBM's POWER-series chips are designed to trade away ultra-high-speed clock rates in favor of low failure rates. The design rule (feature size on chip) is pulled back from the bleeding edge and other layout techniques are employed to make these processors rock solid, to avoid costly downtime from hardware failures in business servers.
    3. These days Apple is well known for its forays into the cluster computing space -- but that's a far cry from the sort of transactional throughput capacity of IBM's high-end servers. I.e. not the same markets!