About halfway through I was thinking this was a really complicated way to display 160x100x16 on a C128 lol, but being able to use the actual DOS content files on a Commodore is invaluable with connecting both platforms in an online environment for example. Really impressive stuff, neat how you got past the common-color restriction of Commodore hardware. I quite enjoy the hybridization of both platforms, like that CGA Composite Artifact Color option that approximates the C64 color palette.🙂
Very nice! One further optimization you could do is to fill the entire bitmap with %00001111. If two pixels are the same color, just set the attribute to the same color for both foreground and background. This way you can clear the bitmap with fast block fills of %00001111 and only have to individually set the color attribute RAM bytes. Going beyond that, there is also a double-width mode with which you can do theoretically do a 320x200 mode, which only takes up 8000 bytes of bitmap, and then treat it as 160x100x16 as here. I can't recall what that does to the color attributes though. There's also something in my memory about timing weirdness in double-width mode which can result in it requiring doing a slightly smaller horizontal width. So in actuality it might end up being something strange like 304x200, leaving you with 152x100. I'm without a C128 at the moment (but expecting to have one again soon) so I can't reliably experiment to reproduce the mode. It's also entirely possible that I just wasn't adjusting something correctly and could've gotten 320x200 working reliably with different settings. Even with the VDC's limitations compared to the VIC-II's strengths, I still find it a fascinating chip, and think more could've and would've been done on the graphics and gaming side in the 80s and 90s if people had understood it better. It's great to see people like yourself doing videos like these, and I hope it'll inspire more people to see what they can make the VDC do. One more thing regarding the double-width mode is that since it reduces the bitmap to only needing 8000 bytes, I wonder if the mode I described above could be done on the 16K chip? With attributes taking up 8000 bytes, we'd be at 16000 total. Seems like it could be doable, but I may be missing something that would change the math.
Thanks for the input! Double width mode also halves the color resolution, unfortunately. That would have been a great memory saver. Wrt 8000 bytes: if you‘re good with greyscale, you can really use textmode to fake graphics just as CGA does for the 160x100 mode. Also, thanks for the great feedback. I also hope that this inspires more people to look into the c128‘s unique capabilities.
@@the8bittheory Ah, thank you for correcting my flawed memory! Maybe you can also help me recall how attribute RAM works with interlace. Is it interleaved the same way as the bitmap is, so for example byte 1 of color RAM in 8x2 mode would choose the colors for lines 1 and 3, or does it behave in a contiguous way and it would color lines 1 and 2? I believe it's interleaved, but I don't trust my memory on it. Contiguous would be extremely useful, but seems unlikely.
Absolutely. A couple of years make a big difference. Only two RAM chips required for the VDC, for example. Also, 3rd party vendors produced much smaller layouts.
@@the8bittheory even still, I get the feeling that IBM over-engineered everything because I guess it was at the high end of the market, and could justify whatever price to its business consumers.
@@shaunbebbington6411 Yes, and they were super flexible on the Atari 2600 too. The Commodore computers were totally rigid in comparisson. I think another machine that has a video chip that can bend like a rubber duck is the CPC. They could make it do insane vertical resolutions, like 3:4 vertical for Arkanoid, change palettes on line-to-line basis and 4 colour true bitmap modes.
18:29 A much more efficient way to do this doesn't use strings at all: VMW AP, CL(INT(B/16))*16 + CL(B AND 15) The INT() is only for clarity and isn't even needed, since subscripts will be 'integerized' anyway.
@csbruce Nice! Yes, precalc makes it a lot faster. The disk image in the Github Repo also has a version that does everything through lookups. CGALOWRES3.PRG I should mention that in the next video, thanks!
I would think that 640x200 in 16 colours should be possible, or 320x200x16 with dual page buffers or screen+sprite buffer, as the VRAM is 64kB. The VDC now feels a bit like a failure, and not an improvement. The only positive is no jailbars and chroma bleed.
Warum ist dieses Video in Englisch während die vorherigen in Deutsch waren? Bin ein wenig verwundert 😅 Trotz alle dem wieder sehr informativ und interessant. Mir haben auch die vorherigen Videos sehr gefallen.😊
😁 naja ich hatte von Anfang an geplant, zweisprachig zu fahren. Zwei Tonspuren gibts leider noch nicht, englische Untertitel gibts aber schon bei anderen Videos. Und die machen fast die Hälfte der dortigen Besucher aus. Deshalb hab ich jetzt mal englisch gemacht. Deutsche Untertitel kommen aber noch. Freut mich dass es dir trotzdem gefallen hat. Danke für das Feedback 💪🏻
@@the8bittheoryDie absurde Situation ist, dass RU-vid gerade wegen der Sprachwahl das Video auch einem breiteren Publikum zeigt. An sich verstehe ich Deutsch genauso gut wie Englisch und könnte mir genauso gut das deutsche Video anhören. Allerdings bekomme ich das englische Video in meinen Vorschlägen zu sehen und so erfahre ich nun von der Existenz dieses Kanals.
Genau, das habe ich auch bemerkt. Ich werde aber wohl beide Sprachen beibehalten. Die Sprachversion, die als zweite kommt, hat immer den Vorteil dass Feedback von der ersten einfließen kann :-)
1:50 This is wrong. CGA can display 16 colors in high res. Generally though, it is limited to color cells in alpha numeric mode (displaying the built in fonts). The color data only takes 4 bits per cell and there are only 2k cells.
So it could if it had more RAM available. Is that what you‘re saying? Do you know of any CGA cards that came with more RAM? Thanks for your input, highly appreciated
@@the8bittheory Honestly, I think it was just a wording error or I misinterpreted what you said.. I was referring to text mode, which technically is running in 640x200 using 8x8 fonts and each cell can be any of 16 colors. I really should delete the comment. Sorry.
Ich bin gerade am Experimentieren und hab auch das Video zum Microcompiler in beiden Sprachen veröffentlicht. Ich werd mal sehen wie groß der Aufwand für die zweite Sprache ist. Vielleicht gibts in Zukunft alle Zweisprachig (die zu Zeit der Gilden werden aber immer Deutsch bleiben) Danke für deinen Kommentar, sowas ist wichtig :-)
