Close to Metal (CTM) is an application programming interface (API) that is designed to expose developers with the underlying parallel processing architecture of graphics hardware.
It was initially released by ATI Technologies to enable general purpose computing on graphics processing units (GPGPU) or custom programming and control on the graphic card/hardware.
CTM primarily enabled exposure and provided access of previously unavailable, low-level graphic card functions to software developers. These included the instructions, processor set architecture and memory. It allowed developers to create applications utilizing an array of untapped GPGPU capabilities and performed faster than standard central processing units (CPU). It also replaced the OpenGL and DirectX API for programmers. The CTM was integrated and supported from ATI R580 GPU processor cards.
After Advanced Micro Devices, Inc. (AMD) acquired ATI, the CTM was succeeded by the OpenCL framework, which provided more enhanced access and control over graphical processor capabilities.