Comment by ajross
13 days ago
That doesn't sound right. The tube the mac was displaying on was much closer to a TV-style 4:3 ratio anyway, there were significant blank spaces at the top and bottom.
If I was placing bets, it was another hardware limitation. Maybe 342 put them right at some particular DRAM timing limit for the chips they were signing contracts for. Or maybe more likely, the ~21.5 kHz scan rate was a hard limit from the tube supplier (that was much faster than TVs could do) and they had a firm 60 Hz requirement from Jobs or whoever.
You guys are ignoring the horizontal and vertical blanking periods, which were usually 25~35% of the active horizontal period and 8~10% of the active vertical period. I could find these two links that explain that the actual signal sent to the CRT was around 704x370 pixels:
https://nerdhut.de/2016/06/26/macintosh-classic-crt-1/
https://bobparadiso.com/wp-content/uploads/2014/09/timing.pn...