IHS

An Integrated Heat Spreader (IHS) is a thick piece of thermally conductive metal such as aluminum plated copper which allows for improved heat transfer between the dies of a multi-chip-module (MCM) and the heatsink. It also adds thermal inertia to the system.

On the Xbox 360, IHS's were used on Shiva and Valhalla, but curiously the GPU MCM does not use one. However, the use of an IHS is not thermally required as the eDRAM puts out less than 9W and is always slightly shorter than the GPU die.

Shiva with IHS

Valhalla with IHS