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IBM Paper with Details of Xbox 360 CPU Design

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#1 Xbox-Scene


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Posted 09 December 2005 - 07:18 AM

IBM Paper with Details of Xbox 360 CPU Design-- Posted by XanTium on December 9 01:18 EST
IBM released a new paper with details about the Xbox 360 CPU they designed for Microsoft:

The Xbox 360 system has a single chip (with 165 million transistors) for its CPU. This chip is in fact a three-way symmetric multiprocessor design. The three PowerPC cores are identical, except that they are physically reflected through the X and Y axis. Each of the CPU cores is a specialized PowerPC chip with a VMX128 extension related to (and partially compatible with) the VMX instructions in the G4 and G5 CPUs. The three CPU cores share a 1MB Level2 cache. Each processor has 32KB each of data and instruction Level1 cache. The chip's front-side bus/physical interface has a 21.6GB/second bandwidth, and runs at 5.4GHz. The high frequency clocks are generated on-chip by four phase-locked loops: two for the core clocks, two for the PHY clock.

The Xbox 360 CPU chip has testing and debug functions, including tracing, configuration control, and performance monitoring features. Access to these functions is through the block in Figure 1 labeled test/debug. The block labeled Miscellaneous IO provides a JTAG port, a POST monitor, and an interface for a serial EEPROM in case patch logic configuration was needed during bring-up.

The last sentence quoted above might give a bit more info as to why some Xbox 360s have the flash EEPROM near the CPU and others not.

Check out more tech details about the CPU on ibm.com.

#2 jimmsta


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Posted 09 December 2005 - 07:44 AM

Very, very interesting... This should provide some insight into the structure of the applications... to some degree. I have to say "Thanks IBM!" wink.gif

#3 JohnnyVegas


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Posted 09 December 2005 - 07:19 PM

Nice find. Thx.

#4 ksteiner


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Posted 09 December 2005 - 08:24 PM

Nice good job IBM smile.gif

#5 ukanndewit


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Posted 09 December 2005 - 10:45 PM

So the EEPROM is explained, at least a little.

#6 stampsm


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Posted 10 December 2005 - 07:06 AM

did anyone else hear the same thing i did? JTAG biggrin.gif

#7 blah101


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Posted 06 January 2006 - 08:09 AM

nice find.. Kudos

#8 sirsmacketh


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Posted 19 January 2006 - 02:54 PM

yay nice find.... does anyone have the equipment here to actually probe this Miscellaneous I/O port and monitor the POST?

I've been trying to scour the forums for any information about people checking out this I/O port and found nothing.

Either that or they're keeping quiet. ph34r.gif

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