GPU

Xenos

The original Xenos, Y1
Introduced	Late 2005
Designed By	ATi Microsoft NEC (eDRAM)
Codename	ATi C1
Type	GPU
Used In	Original Xbox 360
Clock Speed	500MHz
Memory	10MB eDRAM
Successor	XCGPU

Xenos, codenamed C1, is the graphics processor, northbridge, and memory controller used in the Xbox 360. It also has an NEC designed eDRAM which contains additional logic.

The processor was developed by Microsoft and ATi, and the first version was codenamed Y1, which stands for Year 1.

Specifications

GPU

• 500Mhz clock speed
• 48 floating-point vector processors divided into 3 dynamically scheduled SIMD groups (16 each)
• Unified shader architecture
• 16 texture addressing units
• 16 texture filtering units
• 8 pixel rendering pipelines
• Direct access to CPU L2 cache

eDRAM

• 10MB 256GB/s eDRAM
• Contains logic for:
  • 4-sample anti-aliasing
  • Alpha compositing
  • Color
  • Z/stencil buffering

Versions

Y1 (90nm)

Main article: Y1 (GPU)

The initial version of the GPU, known as Y1, entered production in 2005 and is used on the Xenon and Zephyr_A motherboards. Initial versions were defective while later versions became reliable.

Y2 (80nm)

Main article: Y2 (GPU)

In 2007, the GPU was shrunk to 80nm, while the eDRAM remained at 90nm. Known as Y2, it is used on the Zephyr_B motherboard.

Rhea (80nm)

Main article: Rhea (GPU)

Later in 2007, the GPU was revised with an 80nm eDRAM. Known as Rhea, it is used on the Zephyr_C and Falcon motherboards. Later versions of the chip were the first chips installed on newly produced consoles to be reliable. Multiple versions of Rhea were created as Microsoft experimentated during the attempts to make the chip reliable.