The Xbox 360 CPU

The original Xbox used a hybrid mobile Pentium III/Celeron processor, but for the 360 Microsoft went to IBM and got the rights to a PowerPC core.  The move to the PowerPC instruction set meant that there would be no direct binary compatibility with older Xbox titles, but the sacrifice was obviously deemed necessary by Microsoft. 

The CPU itself features three of these PowerPC cores and is currently manufactured on a 90nm process, however Microsoft will most likely be transitioning to 65nm as soon as possible in order to reduce the die size and thus manufacturing costs.  Remember that a die shrink from 90nm down to 65nm will cut the size of the CPU in half, and should be possible for Microsoft sometime before the end of next year. 


Click to Enlarge

All three cores are identical and feature a 2-issue pipeline and can only execute instructions in-order; we've already discussed the reasoning behind this decision here.  The impact of the in-order execution cores is generally a negative one on current game code, but by going with a much simpler core Microsoft was able to stick three of them on a die with hopes of making up for lost performance by enabling some pretty serious multithreading. 

Not only does the Xbox 360's CPU feature 3 cores, but each core is capable of executing two threads at the same time, making the CPU capable of simultaneously executing 6 threads.  Unfortunately, most titles appear to be only using one or two threads for the majority of their game code, with the remaining threads being used for things like audio encoding/decoding, real-time decompression of game data off of the DVD-ROM and video decoding. 

Microsoft has their own license to use and manufacture the CPU used in the Xbox 360, and thus we see their logo on the chip itself.  Microsoft cools the 3-core CPU using a fairly beefy heatsink outfitted with heatpipes (pictured below): 


Click to Enlarge

Airflow is supplied by the two rear fans in the Xbox 360; the air is channeled over the GPU and CPU heatsinks using a duct. The larger heatsink on the right is atop the CPU, the smaller heatsink is for the GPU:


Click to Enlarge

We have previously discussed the Xbox 360's CPU in much greater detail, which you can read about here.

Removing the Heatsinks from the Motherboard The Xbox 360 GPU
POST A COMMENT

91 Comments

View All Comments

  • PrinceGaz - Friday, November 18, 2005 - link

    Just google "cpu dies" - although you get some hits about dead processors, there are many more abot processor manufacturing, more than you get by googling "cpu dice" (the vast majority of those are to do with random number generation).

    The correct trm for more than one CPU die is "dies".
    Reply
  • KristopherKubicki - Sunday, November 20, 2005 - link

    CPU "die" is called that because the CPU is cut from silicon in a specific term called "dicing". "Dice" is in fact the correct word.

    Just because I had nothing better to do this weekend besides beat Kameo in 10 hours, I put together an etymology of all words related to "Die". I'll put that on a website sometime in the near future.

    Kristopher
    Reply
  • yacoub - Monday, November 21, 2005 - link

    That makes little sense. You dice food but you don't call the resulting piece(s) "die" or "dice". However, a processor is made from a die (remember die-cast metal cars when you were a kid?), and if you have more than one of that type of die, you have dies. Even the Google search comparison between "dies" and "dice" confirms that to be true. Reply
  • akugami - Thursday, November 17, 2005 - link

    Anandtech with a comic from www.gucomics.com about their xbox 360 article. Reply
  • yacoub - Thursday, November 17, 2005 - link

    As with the last article here that did this, you want "dies" not "dice".
    quote:

    simply pull the heatsinks off to reveal the GPUs (two dice on the chip)
    Reply
  • yacoub - Thursday, November 17, 2005 - link

    quote:

    332 million transistor GPU is split into two separate dice,


    "Dice" are only in gambling. You want "dies".
    Reply
  • yacoub - Thursday, November 17, 2005 - link

    pl. dies A device used for cutting out, forming, or stamping material, especially:
    An engraved metal piece used for impressing a design onto a softer metal, as in coining money.
    One of several component pieces that are fitted into a diestock to cut threads on screws or bolts.
    A part on a machine that punches shaped holes in, cuts, or forms sheet metal, cardboard, or other stock.
    A metal block containing small conical holes through which plastic, metal, or other ductile material is extruded or drawn.

    pl. dies Architecture. The dado of a pedestal, especially when cube-shaped.


    pl. dice
    A small cube marked on each side with from one to six dots, usually used in pairs in gambling and in various other games.
    dice (used with a sing. verb) A game of chance using dice.


    tr.v. died, die·ing, dies
    To cut, form, or stamp with or as if with a die.
    Reply
  • yacoub - Thursday, November 17, 2005 - link

    quote:

    On a smaller manufacturing process, the dice could be unified,


    DIES. DIES DIES DIES. Yarrr...
    Reply
  • yacoub - Thursday, November 17, 2005 - link

    The worst part is people reading the article who've never heard it used like that before (because it's wrong) are going to think you've got it right and will start saying it. Reply
  • xbdestroya - Thursday, November 17, 2005 - link

    Seriously, is grammar commentary the extent of your thoughts on the article? Reply

Log in

Don't have an account? Sign up now