Close to Metal (CTM) is the name of a beta version of a low-level programming interface developed by ATI, now AMD Graphics Product Group, to enable GPGPU computing. CTM was short-lived and the first production version of AMD`s GPGPU technology was called the AMD Stream SDK, or the current AMD APP SDK for Windows and Linux 32-bit and 64-bit. APP stands for “Accelerated Parallel Processing” and also aims at a heterogeneous system architecture.

What is Close to Metal?

Close to Metal, originally called THIN (Thin Hardware Interface) and Data Parallel Virtual Machine, gave developers direct access to the native instruction set and memory of the massively parallel computing elements in modern AMD graphics cards. CTM bypasses the graphics-centric DirectX and OpenGL APIs for the GPGPU programmer to provide previously unavailable low-level functionality, including direct control of the stream processors/ALUs and memory controllers. R580 (ATI X1900) and later generations of AMD`s GPU microarchitecture supported the CTM interface.

CTM`s commercial successor, AMD Stream SDK, was released in December 2007 under AMD EULA after the software stack was rewritten. The Stream SDK provides both low-level and high-level tools for universal access to AMD graphics hardware.

The use of GPUs to perform computations has great potential for some applications because GPU microarchitectures are fundamentally different from CPUs. GPUs achieve much higher througput (calculations per second) by running many programs in parallel and limiting flow control (the ability of a program to execute instructions independently of others). Modern GPUs also have addressable on-die memory and extremely powerful multi-channel external memory.

AMD then switched from CTM to OpenCL.

Open Source.

Some components of CTM and the Stream SDK are open Source, like the Book+ C-like language and compiler.

Thank you for your visit.