3 ms·

FantasyLand on VGA

47 points by kencausey 5y ago

h2odragon 5y ago
EGA cards were truly funky beasts. There was a "64 color" stunt where you could switch the 16 color palette fast enough to have up to 4 different palettes visible on screen at once. There were fringe flavors of compatibles, with extra capabilites. 400 scanline modes that enabled 43 and 50 lines text modes hover in my memory.
- bitwize 5y ago
  Pfff... getting more colors on screen than you have palette entries is not a stunt at all... not on a thoughtfully designed system with raster interrupts. On the Amiga you could even program the copper to do this work for you, freeing up the CPU for other tasks.
- shdon 5y ago
  400 scanline modes gave us 50 lines of text by virtue of loading the 8x8 pixel font (400/8=50). There was no incompatible trickery going on for 43 line mode. That was just the 8x8 pixel font at the standard 350 scanlines (350/8=43.75). The palette was weird because changing palette entries away from the standard 16 CGA colours was impossible in 200 scanline modes. It was only possible in 350 scanline mode (and also on VGA, but I digress). That's because the EGA could connect (and often would be connected) to CGA monitors and adjusted the pinout of the connector accordingly. This meant just 1 bit per colour channel and 1 intensity bit. The full EGA palette required 2 bits per colour channel and could only be used on actual EGA monitors. The way IBM ensured that was limiting palette changes to the 640x350 mode.
- TonyTrapp 5y ago
  How about 1024 colors on CGA? https://int10h.org/blog/2015/04/cga-in-1024-colors-new-mode-illustrated/ https://int10h.org/blog/2015/04/cga-in-1024-colors-new-mode-...
djmips 5y ago
This reminds me that, back in the eighties, a friend of mine made a super cool EGA BBS terminal program with split screens and smooth scrolling - but it also used the vertical retrace interrupts. It's a shame there wasn't more compatibility around a lot of this on PC since it would have enabled some very cool software that everyone could use.
ttul 5y ago
Id Software managed to get smooth scrolling working on EGA - a mind blowing achievement at that time. https://en.wikipedia.org/wiki/Adaptive_tile_refresh https://en.wikipedia.org/wiki/Adaptive_tile_refresh
- joakleaf 5y ago
  id Software and Carmack often gets credit for this, but I remember seeing a number of games already using smooth-scrolling in EGA before. Zanygolf from 1988 and Rick Dangerous 1989 comes to mind (albeit vertical scrolling). Harvard Graphics 2.3 (from 1990) could also use smooth-scrolling in EGA (640x350) when running presentations. I am pretty sure Lemmings (early 1991) also used the horizontal smooth-scrolling capabilities of EGA/VGA. For reference, id software's Commander Keen is from late 1990. I remember trying to work with the smooth scrolling registers on VGA (256 color mode) in 1991/1992 myself. The registers were described in the EGA/VGA programmers reference (1988), and I suspect the author of that book must have known that the hardware was capable of this. Unfortunately, smooth-scrolling required using a combination of several registers, so as far I remember, the documentation of this was scattered all over the book under the different registers, and wasn't really easily approachable for the reader. Of course, the techniques behind smooth-scrolling and page-swapping for VGA (e.g. mode-X) were really popularized when Michael Abrash published an article about it in 1991 in Dr. Dobbs. Gaming on the PC from '87 to 1992 would probably have been very different, if IBM had just described smooth-scrolling and other hidden gems of the EGA/VGA cards in more detail.
  - JohnBooty 5y ago
    That's super interesting. How did Harvard Graphics use smooth scrolling? I see that it smoothly animated some screen elements, but not a whole screen-filling background ala Commander Keen. https://youtu.be/wwqm0zOivUU?t=1007 https://youtu.be/wwqm0zOivUU?t=1007 I'm not familiar with Harvard Graphics or EGA graphics details, so, might be a dumb question. As an aside, it's eternally hilarious to me that there were so many capabilities in the EGA/VGA chipsets that were "hidden." IBM clearly spent a lot of engineering time (and die space!) implementing them... and then it still took ages for them to be "discovered." Did IBM just neglect to promote them to developers? Or did they intentionally sort of bury those features so as not to be seen as having built a "game machine?" Always curious.
glhaynes 5y ago
YouTube video of this program. Not sure what hardware (or emulation) it's running on but it doesn't appear buggy. https://www.youtube.com/watch?v=RRnHzt7X0OE https://www.youtube.com/watch?v=RRnHzt7X0OE

47 points by kencausey 5y ago

EGA cards were truly funky beasts. There was a "64 color" stunt where you could switch the 16 color palette fast enough to have up to 4 different palettes visible on screen at once. There were fringe flavors of compatibles, with extra capabilites. 400 scanline modes that enabled 43 and 50 lines text modes hover in my memory.

bitwize 5y ago
Pfff... getting more colors on screen than you have palette entries is not a stunt at all... not on a thoughtfully designed system with raster interrupts. On the Amiga you could even program the copper to do this work for you, freeing up the CPU for other tasks.
shdon 5y ago
400 scanline modes gave us 50 lines of text by virtue of loading the 8x8 pixel font (400/8=50). There was no incompatible trickery going on for 43 line mode. That was just the 8x8 pixel font at the standard 350 scanlines (350/8=43.75). The palette was weird because changing palette entries away from the standard 16 CGA colours was impossible in 200 scanline modes. It was only possible in 350 scanline mode (and also on VGA, but I digress). That's because the EGA could connect (and often would be connected) to CGA monitors and adjusted the pinout of the connector accordingly. This meant just 1 bit per colour channel and 1 intensity bit. The full EGA palette required 2 bits per colour channel and could only be used on actual EGA monitors. The way IBM ensured that was limiting palette changes to the 640x350 mode.
TonyTrapp 5y ago
How about 1024 colors on CGA? https://int10h.org/blog/2015/04/cga-in-1024-colors-new-mode-illustrated/ https://int10h.org/blog/2015/04/cga-in-1024-colors-new-mode-...

djmips 5y ago

This reminds me that, back in the eighties, a friend of mine made a super cool EGA BBS terminal program with split screens and smooth scrolling - but it also used the vertical retrace interrupts. It's a shame there wasn't more compatibility around a lot of this on PC since it would have enabled some very cool software that everyone could use.

ttul 5y ago

Id Software managed to get smooth scrolling working on EGA - a mind blowing achievement at that time. https://en.wikipedia.org/wiki/Adaptive_tile_refresh https://en.wikipedia.org/wiki/Adaptive_tile_refresh

joakleaf 5y ago
id Software and Carmack often gets credit for this, but I remember seeing a number of games already using smooth-scrolling in EGA before. Zanygolf from 1988 and Rick Dangerous 1989 comes to mind (albeit vertical scrolling). Harvard Graphics 2.3 (from 1990) could also use smooth-scrolling in EGA (640x350) when running presentations. I am pretty sure Lemmings (early 1991) also used the horizontal smooth-scrolling capabilities of EGA/VGA. For reference, id software's Commander Keen is from late 1990. I remember trying to work with the smooth scrolling registers on VGA (256 color mode) in 1991/1992 myself. The registers were described in the EGA/VGA programmers reference (1988), and I suspect the author of that book must have known that the hardware was capable of this. Unfortunately, smooth-scrolling required using a combination of several registers, so as far I remember, the documentation of this was scattered all over the book under the different registers, and wasn't really easily approachable for the reader. Of course, the techniques behind smooth-scrolling and page-swapping for VGA (e.g. mode-X) were really popularized when Michael Abrash published an article about it in 1991 in Dr. Dobbs. Gaming on the PC from '87 to 1992 would probably have been very different, if IBM had just described smooth-scrolling and other hidden gems of the EGA/VGA cards in more detail.
- JohnBooty 5y ago
  That's super interesting. How did Harvard Graphics use smooth scrolling? I see that it smoothly animated some screen elements, but not a whole screen-filling background ala Commander Keen. https://youtu.be/wwqm0zOivUU?t=1007 https://youtu.be/wwqm0zOivUU?t=1007 I'm not familiar with Harvard Graphics or EGA graphics details, so, might be a dumb question. As an aside, it's eternally hilarious to me that there were so many capabilities in the EGA/VGA chipsets that were "hidden." IBM clearly spent a lot of engineering time (and die space!) implementing them... and then it still took ages for them to be "discovered." Did IBM just neglect to promote them to developers? Or did they intentionally sort of bury those features so as not to be seen as having built a "game machine?" Always curious.

glhaynes 5y ago

YouTube video of this program. Not sure what hardware (or emulation) it's running on but it doesn't appear buggy. https://www.youtube.com/watch?v=RRnHzt7X0OE https://www.youtube.com/watch?v=RRnHzt7X0OE