AnandTech: Microsoft's Xbox 360 goes 65nm: Falcon Dissection and Power Consumption

Die shrinks are big deals in the PC industry; transitioning to smaller manufacturing processes means faster switching times and greater transistor density, usually resulting in cooler, faster and more feature-filled CPUs and GPUs.

Intel just recently began its transition from 65nm to 45nm transistors with the release of its Penryn based Core 2 CPUs. The benefits of smaller manufacturing processes are made clearly visible by the Penryn example; despite having 50% more cache than its predecessor and more features (e.g. SSE4), each Penryn die measures 107 mm^2 compared to a 65nm Conroe at 143 mm^2. Transistor density also went up tremendously, as Penryn crams 410 million transistors into less space than 291 million transistors with Conroe.

We just saw a more dramatic showcase of the improvements smaller transistors can bring to GPUs with AMD's new Radeon HD 3800 graphics cards. The RV670 GPU is built off of TSMC's 55nm process and very similar, architecturally, to the 80nm R600 used in the Radeon HD 2900 XT. The die size and transistor density have both improved tremendously thanks to the new process, as has power consumption. The table below should give you some hard numbers to look at:

Microprocessor	Manufacturing Process	Die Size	Transistor Count	Transistor Density
Intel Core 2 Duo (Conroe)	65nm	143 mm^2	291M	~2.03M per mm^2
Intel Core 2 Duo (Penryn)	45nm	107 mm^2	410M	~3.83M per mm^2
AMD Radeon HD 2900 XT (R600)	80nm	408 mm^2	700M	~1.71M per mm^2
AMD Radeon HD 3870 (RV670)	55nm	192 mm^2	666M	~3.46M per mm^2

In both examples, the move to a smaller transistor feature size results in a tremendous increase in transistor density on the order of 90 - 100%. On the PC side, these increases are nothing new, Moore's Law has been hard at work for decades now and we keep reaping the benefits in the form of better, faster, cheaper products. With Game Consoles however, the story is a little different.

Game console hardware must remain largely unchanged throughout the life cycle of the system, which these days is somewhere in the 4 - 5 year range. The whole point to a closed game console system is that you have one spec of hardware to develop for, introducing faster CPUs and GPUs in the middle of the life cycle just wouldn't fly. Since adding features and performance isn't possible, the only real benefits to process shrinks for chips in game consoles are cost, heat and noise reduction, all of which are still important.

Microsoft just recently dropped the price of its Xbox 360 and around the same time, rumors crept up about a quiet introduction of 65nm CPUs into the bill of materials. The original Xbox 360 manufactured from 2005 up until August of this year all used 90nm chips; the CPU, GPU and eDRAM were all fabbed on a 90nm process, which was state of the art at the time. However, as you've undoubtedly noticed with Intel's recent move to 45nm, 90nm is more than dated now.

A move to 65nm would undoubtedly reduce power consumption, potentially make the console quieter and obviously make it cheaper to produce. With the Xbox 360 there's also another side effect that many surmised would result from a move to 65nm: increased reliability.

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