The Ember Console — System Architecture Design: Basic Requirements
- Tom Gambill
- Mar 7
- 2 min read
We have made significant progress in the Ember CPU design; this week, we look at the higher-level picture of the Ember Homebrew Game Console and which other systems we still need to design to create a working system capable of playing 80s and 90s-era video games. For example, we will need to handle reading input from a keyboard or game controller, generate the game display and output to the screen, and determine how other internal parts, like storage, memory, etc., will work.
Display
The display output is typically generated by a separate processor from the CPU. In modern computers and consoles, this processor is called a GPU, or Graphics Processing Unit. However, before 3D graphics and triangles, most computers and game consoles generated only a 2D output. This was often accomplished with a combination of background layers and movable images called sprites. The Nintendo Entertainment System or NES, SNES, Collecovision, Sega Genesis, and many others, including some personal computers of the time from Atari and Commodore, also used sprites and backgrounds.
Perhaps a more appropriate name for this level of graphics output was Pixel Processing Unit, or PPU, which Nintendo and a few others used at the time for the chip that powered the display output.
A popular off-the-shelf sprite and graphics chip of the time was the TMS9918 from Texas Instruments. This chip became the model for many game consoles and computers in the 1980s and 90s. We will take a lot of inspiration from this chip for our GPU (or PPU?) design.
Sound
Sound is another important output from a game machine or computer, so we will need a processor to handle sound and music output. A popular design of the time was the AY-3–8910 by General Instrument, which was copied by Yamaha as the YM2149. This was a 3-channel sound chip used in many computers of the time, including the Atari ST, MSX2, and some versions of the Sinclair ZX Spectrum. These chips were even used in pinball games and even the arcade game Gyruss to great effect. We will take a lot of inspiration from these chips in our sound design.
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