本文转载自：01.org，主要介绍Intel GPU的三个firmware：GUC、HUC和DMC。

1. CRIPTION

New generations of Intel® graphics hardware make use of firmware with power and performance benefits and functionalities like scheduling and media offloading.

2. PHICS MICROCONTROLLER (GUC)

The Graphics micro (µ) Controller (GuC) is designed to offload some of the functionality usually run on the host driver. This functionality includes:

2.1 Authentication of the HEVC/H.265 micro (µ) Controller (HuC)

Enables use of HuC codec(video decoder and encoder) acceleration extensions by the iHD Intel media driver.

2.2 Low latency graphics context scheduling

GuC context scheduling operations will include determining which context to run next, submitting a context to a command streamer for a next available engine and pre-empting and resubmitting existing contexts as required.

2.3 Power management

When performing scheduling, the GuC is well placed to track busyness and enable efficient frequency and power gating decisions.

3. C/H.265 MICROCONTROLLER (HUC)

The HEVC/H.265 micro (µ) Controller (HuC) offloads some of the media functions from CPU to the GPU and is utilized by the iHD Intel media driver. These include but are not limited to bitrate control and header parsing. For example in the case of bitrate control, driver invokes HuC in the beginning of each frame encoding pass, encode bitrate is adjusted by the calculation done by HuC. Both the HuC hardware and the encode hardcode reside in GPU. Using HuC will save unnecessary CPU-GPU synchronization. Note that the GuC is required to enable the loading of HuC.

4. PLAY MICROCONTROLLER (DMC)

DMC provides additional graphics low-power idle states. It provides capability to save and restore display registers across these low-power states independently from the OS/Kernel.