The 6845 '''CRTC''' (Cathode Ray Tube Controller) chip was created by Motorola in 1977. It works with the [[Gate Array]] to generate the video signal on the Amstrad CPC.
This chip is also used in the [[BBC Micro]], Camputers [[Lynx]], [[Sharp X1EG2000 Colour Genie]], [[EACA Colour GenieSharp X1]], [[MicroBee]], [[Commodore PET]] and the early graphics cards (MDA, Hercules, CGA, Plantronics Colorplus) for [[IBM PC]]. And it is found in some [https://www.msx.org/wiki/Hitachi_HD6845 MSX1 expansions], providing an 80-column text mode.
It's important to note that the CRTC chip is primarily designed for character-based displays. It explains why, on the Amstrad CPC, the video memory is organized into a grid of characters rather than a purely linear bitmap.