View source for Engineering:Xenon (processor)

{{short description|CPU used in the Xbox 360}}
{{Infobox CPU
| name                      = Microsoft XCPU<br />(codenamed Xenon)
| image                     = KL Microsoft XBOX 360 CPU ES.jpg
| image_size                = 150px
| caption                   = Picture of the microprocessor (XCPU-ES shown).
| produced-start            = 
| produced-end              = 
| slowest                   = 
| fastest                   = 
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| size-from                 = 
| size-to                   = 
| soldby                    =
| designfirm                = [[Company:IBM|IBM]]
| manuf1                    = [[Company:IBM|IBM]], [[Company:GlobalFoundries|GlobalFoundries]]
| core1                     = 
| sock1                     = 
| pack1                     =
| brand1                    =
| arch                      = [[PowerPC]]
| microarch                 = 
| cpuid                     =
| code                      =
| numcores                  = 3 cores
| l1cache                   = 32/32 KB
| l2cache                   = 1 MB
| l3cache                   =
| application               =
}}
{{POWER, PowerPC, and Power ISA}}
'''Microsoft XCPU''', codenamed '''Xenon''', is a [[Central processing unit|CPU]] used in the [[Engineering:Xbox 360|Xbox 360]] game console, to be used with ATI's Xenos graphics chip.

The processor was developed by [[Company:Microsoft|Microsoft]] and [[Company:IBM|IBM]] under the IBM chip program codenamed "Waternoose", which was named after the ''Monsters, Inc.'' character Henry J. Waternoose III.<ref>{{cite news|url=http://www.designnews.com/article/12317-Learning_from_Failure.php|title=Learning from failure - The inside story on how IBM out-foxed Intel with the Xbox 360|last=Takahashi|first=Dean|work=Electronic Business|date=May 1, 2006|url-status=dead|archive-url=https://web.archive.org/web/20090827105101/https://www.designnews.com/article/12317-Learning_from_Failure.php|archive-date=August 27, 2009}}</ref> The development program was originally announced on November 3, 2003.<ref>{{cite web|url=http://www-03.ibm.com/press/us/en/pressrelease/6298.wss|title=IBM News room - 2003-11-03 Microsoft and IBM Announce Technology Agreement - United States|work=ibm.com}}</ref>

The processor is based on IBM [[PowerPC]] [[Instruction set architecture|instruction set architecture]]. It consists of three independent processor cores on a single die. These cores are slightly modified versions of the [[Engineering:Cell (microprocessor)#Power Processor Element (PPE)|PPE]] in the [[Engineering:Cell (microprocessor)|Cell processor]] used on the [[Engineering:PlayStation 3|PlayStation 3]].<ref>"[http://www.gamasutra.com/view/feature/3904/processing_the_truth_an_interview_.php Processing The Truth: An Interview With David Shippy]", Leigh Alexander, ''Gamasutra'', January 16, 2009</ref><ref>"[https://www.wsj.com/articles/SB123069467545545011 Playing the Fool]", Jonathan V. Last, ''Wall Street Journal'', December 30, 2008</ref> Each core has two symmetric hardware threads ([[Simultaneous multithreading|SMT]]), for a total of six hardware threads available to games. Each individual core also includes 32 KB of [[CPU cache|L1 instruction cache]] and 32 KB of L1 data cache.

The XCPU processors were manufactured at IBM's East Fishkill, New York fabrication plant and Chartered Semiconductor Manufacturing (now part of [[Company:GlobalFoundries|GlobalFoundries]]) in Singapore.<ref>{{cite web|url=http://www-03.ibm.com/press/us/en/pressrelease/7941.wss|title=IBM News room - 2005-10-25 IBM Delivers Power-based Chip for Microsoft Xbox 360 Worldwide Launch - United States|work=ibm.com}}</ref> Chartered reduced the fabrication process in 2007 to 65 nm from 90 nm, thus reducing manufacturing costs for Microsoft.

==Specifications==
*90 nm process,<ref name="xbox360cpu">{{cite web|url=http://www.ibm.com/developerworks/power/library/pa-fpfxbox/ |title=Application-customized CPU design: The Microsoft Xbox 360 CPU story |access-date=September 8, 2007 |author=Jeffrey Brown |website=[[Company:IBM|IBM]] |date=December 6, 2005 |url-status=dead |archive-url=https://web.archive.org/web/20071025035913/http://www.ibm.com/developerworks/power/library/pa-fpfxbox/ |archive-date=October 25, 2007 }}</ref> 65 nm process upgrade in 2007<ref name="chartered65nm">{{cite web|url=http://news.teamxbox.com/xbox/10754/Chartered-to-Manufacture-65nm-Xbox-360-CPUs/ |title=Chartered to Manufacture 65-nm Xbox 360 CPUs |access-date=January 9, 2008 |author=César A. Berardini |date=August 21, 2006 |url-status=dead |archive-url=https://web.archive.org/web/20080123124440/http://news.teamxbox.com/xbox/10754/Chartered-to-Manufacture-65nm-Xbox-360-CPUs/ |archive-date=January 23, 2008 }}</ref> (codenamed "Loki"), 45 nm process since Xbox 360 S model<ref name="engadgetnewxbox">{{cite web | url = https://www.engadget.com/2010/06/14/slim-xbox-360-gets-official-at-299-shipping-today-looks-angul/ |title=New Xbox 360 looks angular and Ominous |first=Nilay |last=Patel |date=June 14, 2010 |publisher=Engadget.com |access-date= June 14, 2010 }}</ref>
*165 million [[Engineering:Transistor|transistor]]s
*Three cores, each two-way [[Simultaneous multithreading|SMT]]-capable and clocked at 3.2&nbsp;[[Hertz|GHz]]<ref  name="xbox360cpu"/>
*[[SIMD]]: Two [[Engineering:AltiVec#VMX128|VMX128]] units with a dedicated (128×128 bit) [[Register file|register file]] for each core,<ref  name="xbox360cpu"/> one for each thread
*1&nbsp;[[Megabyte|MB]] L2 cache<ref  name="xbox360cpu"/> (lockable by the GPU) running at half-speed (1.6&nbsp;GHz) with a 256-bit bus
*51.2 GB/s of L2 memory bandwidth (256&nbsp;bit × 1600&nbsp;MHz)
*21.6 GB/s [[Engineering:Front-side bus|front-side bus]] (On the CPU side, this interfaces to a 1.35&nbsp;GHz, 8B wide, FSB dataflow; on the GPU side, it connects to a 16B wide FSB dataflow running at 675&nbsp;MHz.)<ref  name="xbox360cpu"/>
*[[Dot product]] performance: 9.6&nbsp;billion per second
*[[Out-of-order execution#In-order processors|In-order instruction execution]]<ref  name="xbox360cpu"/>
*768 bits of IBM eFUSE-based OTP memory<ref name="google">{{cite web|url=https://www.youtube.com/watch?v=uxjpmc8ZIxM |archive-url=https://ghostarchive.org/varchive/youtube/20211219/uxjpmc8ZIxM |archive-date=2021-12-19 |url-status=live|title=Xbox360 security system|website=[[Company:YouTube|YouTube]] }}{{cbignore}}</ref>
*[[Read-only memory|ROM]] (and 64&nbsp;[[Kibibyte|KB]] SRAM) storing Microsoft's Secure Bootloader, and encryption hypervisor<ref name="google"/>
*[[Endianness|Big-endian]] architecture

==XCGPU==
The Xbox 360 S introduced the '''XCGPU''', which integrated the Xenon CPU and the [[Engineering:Xenos (graphics chip)|Xenos GPU]] onto the same die, and the [[EDRAM|eDRAM]] into the same package. The XCGPU follows the trend started with the integrated EE+GS in PlayStation 2 Slimline, combining CPU, GPU, memory controllers and IO in a single cost-reduced chip. It also contains a "front side bus replacement block" that connects the CPU and GPU internally in exactly the same manner as the [[Engineering:Front-side bus|front side bus]] would have done when the CPU and GPU were separate chips, so that the XCGPU doesn't change the hardware characteristics of the Xbox 360.

XCGPU contains 372 million transistors and is manufactured by [[Company:GlobalFoundries|GlobalFoundries]] on a 45&nbsp;nm process. Compared to the original [[Engineering:Chipset|chipset]] in the Xbox 360 the combined power requirements are reduced by 60% and the physical chip area by 50%.<ref name="ArsXCGPU">{{cite web|url=https://arstechnica.com/gaming/news/2010/08/microsoft-beats-intel-amd-to-market-with-cpugpu-combo-chip.ars|title=Microsoft beats Intel, AMD to market with CPU/GPU combo chip|date=August 24, 2010|access-date=August 24, 2010|author=Jon Stokes, Ars Technica}}</ref><ref name="360S-teardown">{{cite web|url=http://www.pcper.com/article.php?aid=940 |title=The New Xbox 360 S "Slim" Teardown: Opened and Tested |access-date=June 24, 2010 |author=PC Perspective |date=June 21, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100625003750/http://www.pcper.com/article.php?aid=940 |archive-date=June 25, 2010 }}</ref>

== Gallery ==
Illustrations of the different generations of processors in Xbox 360 and Xbox 360 S.
<gallery>
XCPU-ES Xenon.jpg|The original XCPU-ES manufactured at 90&nbsp;nm by IBM in 2005. ES stands for "Engineering Sample" and the device is packaged by IBM at their Bromont facility in Canada. It runs at 2.8GHz, as opposed to the final chip, which ran at 3.2GHz.
XCPU Zephyr.jpg|The 90nm XCPU manufactured at 90&nbsp;nm by Chartered in Singapore 2006.
XCPU Falcon.jpg|The 65nm XCPU manufactured at 65&nbsp;nm by Chartered in Singapore 2007.
XCGPU.jpg|The two chips of the XCGPU: The larger is the XCGPU itself and the smaller is the 10&nbsp;MB eDRAM. Manufactured at 45&nbsp;nm by Global Foundries in Singapore in 2010.
XCGPU-heatspreader.jpg|The XCGPU with heatspreader. The complete device is packaged by IBM at their Bromont facility in Canada.
</gallery>

==References==
{{reflist|30em}}
*[http://forums.xbox-scene.com/index.php?showtopic=231928 Xenon hardware overview] {{Webarchive|url=https://web.archive.org/web/20060220043626/http://forums.xbox-scene.com/index.php?showtopic=231928 |date=February 20, 2006 }} by Pete Isensee, Development Lead, Xbox Advanced Technology Group, written some time before June 23, 2007

==External links==
*[https://arstechnica.com/articles/paedia/cpu/xbox360-2.ars Ars Technica explains the Xenon CPU]

{{Xbox}}

[[Category:PowerPC microprocessors]]
[[Category:IBM microprocessors]]

{{Sourceattribution|Xenon (processor)}}