Apple abandons AMD Radeon in the transition to its own ARM processors

During Apple’s WWDC 2020 developer event, the company revealed that Intel’s x86 processors are being abandoned in favor of home-built ARM processors, currently known as Apple Silicon. Its own processors replace Intel in Mac computers over a two-year transition period, but Apple did not mention how the graphics side is handled. This will be changed in a developer session from WWDC 2020.

In the session “Bring your Metal app to Apple Silicon Macs”, Apple describes how developers most smoothly develop with the graphics interface Metal for the company’s upcoming ARM computers. In a table comparing development for the two hardware families, the presentation lists only Apple-developed graphics cards for the upcoming ARM-based computers, thus confirming that AMD’s dedicated Radeon graphics cards will be abandoned in connection with Intel’s exit from the Mac family.

Just as during the presentation of the transition to ARM, Apple demonstrates here how games compiled for Intel’s x86 processors run with good performance on the company’s ARM processors. An Intel version of the rally game Dirt Rally is used to demonstrate how the home-built graphics hardware supports the modern rendering techniques used to paint the graphic landscape of the game, while interpreting the code via the Rosetta 2 emulation layer.

Apple’s graphics parts for its own silicon are based on technology used in the company’s ARM processors in the A-series for mobile devices. This means a continued use of so-called Tile-Based Deferred Rendering (TBDR), where the image to be rendered is divided into a grid of sections or “tiles” rendered in parallel. This model strikes a better balance between performance and energy efficiency, something that is important for mobile devices.

With this, Apple also deviates from the rendering model Immediate Mode Rendering (IMR) which the company has used with Mac OS and Mac computers, where both integrated Intel graphics and dedicated graphics circuits from AMD are used. Here, functions such as depth and which surfaces are covered by others in the entire image are calculated, which is more demanding for the graphics hardware.

Additional advantages Apple states for TBDR rendering are that the division of the image into a grid enables effective application of anti-aliasing (AA). By performing these calculations on the different squares of the grid, the technology can Multisample anti-aliasing (MSAA) performed with good performance, without having to use memory outside the graphics circuit.

Both current graphics chips from Intel’s and AMD’s range and Apple’s home – built technology are supported in Apple’s graphics interface Metal. Developer interfaces such as OpenGL and OpenCL are still supported, but are kept alive only for compatibility reasons (deprecated) and optimal performance is only achieved with Metal and other interfaces in Mac OS signed by Apple themselves.

Apple has previously announced that the first Macs with their own silicon will be launched at the end of 2020. Previous reports indicate that this may be about laptops in the Macbook family and the smallest model in the Imac family, which seems to be logical products to introduce a home-made and energy-efficient graphics technology.

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