MediaWiki:Sitenotice:
2025-12-29: I have restored the wiki to a backup from the end of November. Starting in September 2025, accesses went form the 800MB-1.2GB range per month to 26GB in September, 42GB in October, and 70GB in November with most accesses originating from China. As soon as I realized what was causing all the access problems in November, I shut it down (it had reached 36GB by then) behind a password/login screen. The database had gotten corrupted, and I tried a restore from just before the spike in access but that didn't work. Thus, end of November. I still have the other daily backups so if there were any important additions in December, let me know and maybe they can be recovered. - Allen H.
Motorola 6847
The MC6847 is a video display generator chip that is designed for the 6800 family of microprocessors. It reads data from memory (via the SAM chip) and displays the contents on screen. The 6847 is used on Coco 1 and 2's only; this function was replaced by the custom GIME chip in Coco 3 models.
The chip provides a 32x16 alphanumeric display, or graphic displays up to 256x192 pixels in resolution. Additionally, a variety of "semigraphics" modes are provided.
On the Coco, the familiar dark-green on light-green text is generated as a fundamental function of this chip.
In Coco 1's and most Coco 2's, the 6847 is not capable of displaying lowercase. Instead, lower case text appears inverted. Later Coco 2's replaced the 6847 with a 6847T1 that can display proper lower case text.
See Also
- Wikipedia article on the Motorola 6847
- Datasheet http://instruct1.cit.cornell.edu/courses/ee476/ideas/mc6847.pdf