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The original GPU, Y1
IntroducedLate 2005
Designed ByATi
Gunga (65nm only)
Used InOriginal Xbox 360
Clock Speed500MHz
Memory10MB eDRAM

The GPU, codename Xenos (later Gunga) is the graphics processor, northbridge, and memory controller used in the Xbox 360. It also contained an eDRAM daughter die that contains additional logic.

The processor was developed by Microsoft and ATi, and the first version was codenamed Y1, which stands for Year 1. The eDRAM was designed by NEC. Microsoft would later take over development of both dies with Gunga and Styx

GPU Specifications

  • 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

GPU Variants

Y1 (90nm)

The initial version, Y1, entered production in 2005 and is used on the Xenon and Zephyr_A motherboards. Initial versions were defective while later versions became reliable. It uses the Edifis eDRAM.

Y2 (90nm)

In 2007, the GPU was revised and the physical size of the die reduced. The process remained at 90nm and the eDRAM remained unchanged. Y2 is used on the Zephyr_B motherboard.

Rhea (90nm)

Later in 2007, The Y2 version was revised with the Styx-90 eDRAM. Named 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.

Elpis (90nm)

In 2009, fixed 90nm chips stopped being produced, however Microsoft still had Xenons to repair and refurbish. Since the fixed Rhea chip was still being produced, Microsoft chose to slightly modify it in order to allow a revised chip to be retrofitted in place of a defective one. This modification to Xenon boards was named Elpis, which served as the name of the GPU and the motherboard with this GPU installed.

Zeus (65nm)

In 2008, the chip was redesigned for the 65nm process under the codename Gunga. It still uses the Styx-90 eDRAM. Named Zeus, it is used on the Jasper motherboard. It is the first chip where all variants are reliable.

Kronos (65nm)

In 2009, the Zeus chip was revised with a Styx-65 eDRAM. Named Kronos, it is used on the Jasper (July 2009 only) and Tonasket motherboards.


In 2010, the XCPU was combined with the GPU to create a system-on-a-chip, called the XCGPU.

eDRAM Specifications

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

eDRAM Variants


Edifis is the first eDRAM die used on the GPU and was designed by NEC. It was only manufactured on the 90nm process. It is used on the Y1 and Y2 GPUs.


Styx is the redesigned eDRAM die and replaces Edifis. The redesign was done by Microsoft, not NEC. It was manufactured on the 90nm and 65nm processes, known as Styx-90 and Styx-65 respectively. It is used on all versions of Rhea, Elpis, Zeus, and Kronos. It is also used on the Vejle XCGPU.


The Oban CGPU integrated the eDRAM into the main die. As a result, there is no daughter die anymore.