[HN Gopher] The Character Generator ROM ___________________________________________________________________ The Character Generator ROM Author : alraj Score : 30 points Date : 2023-08-11 06:22 UTC (1 days ago) (HTM) web link (www.atariarchives.org) (TXT) w3m dump (www.atariarchives.org) | JdeBP wrote: | Some of those block diagrams were a bit oversimplified. One | cannot address 9 rows with only 3 address lines, for example. Or | do block graphics with just 4 NOR gates. | jandrese wrote: | I think there is a typo in the first graphic on that page, on the | top row the second column is labeled 0011 when it should be 0001. | sedatk wrote: | A 44-year old typo, to be exact. :) | chrisco255 wrote: | (1979) | rbanffy wrote: | Oh... That's just the start of the trickery. DEC and HP (and the | Apple II, in high-res mode) had tricks to shift (delay, really) | groups of pixels by half a pixel, giving us better A's and V's, | and more rounded O's. | raphlinus wrote: | So the HP 2645 _did_ use a half-bit shift and it 's quite | clever. It's shown in this video[1] by CuriousMarc (I've set | the timestamp to the relevant part). The document shown in the | video is available on the Internet Archive[2]. It also reminds | me of techniques used in Epson dot matrix printer fonts, where | the _rate_ of pin firing couldn 't be increased, but the half- | pixel timing could be. | | I'm pretty sure DEC VT100 and VT220 did not do this. There _is_ | some dot-stretching logic in the VT100 and VT220[3], which | improves appearance but doesn 't increase effective resolution. | | Apple ][ is a slightly different story. The high bit (very | similar to the HP terminal) does cause a half-pixel shift, but | I believe this was almost entirely used to create more colors | through NTSC artifacts, not to increase horizontal resolution. | I'm unaware of a character ROM that uses the technique, but I | could be missing something. The best writeup I've found is [4]. | | [1]: https://www.youtube.com/watch?v=QikO0WOAGWI&t=371s | | [2]: | https://archive.org/details/bitsavers_hpterminaleriesCharact... | | [3]: https://www.masswerk.at/nowgobang/2019/dec-crt-typography | | [4]: | https://retrocomputing.stackexchange.com/questions/6271/what... ___________________________________________________________________ (page generated 2023-08-12 23:01 UTC)