by Richard F. Drushel (drushel@apk.net)
[Happy Groundhog Day to everyone! I haven't heard whether or not Puxatawney Phil saw his shadow or not this morning, but here's hoping he didn't--meaning the end of winter, according to folklore.]
Although I have heard through the grapevine that some of my previous articles dealing with the TMS9918/28/29 VDP color palettes were causing MEGO Syndrome (My Eyes Glaze Over) among my readers, I still have one last bit of color palette discussion that I want to empty out of my buffer. So, to those of you who are MEGO-sensitive regarding this topic, please bear with me (or else skip ahead to the next section of the article).
As you may recall, I set out to determine RGB color triplets for the ColecoVision/ADAM VDP colors based upon technical information provided in TI's VDP Data Manual. I did this because I was dissatisfied with the colors used in Marcel de Kogel's COLEMDOS.EXE ColecoVision emulator (which was derived from an MSX2 emulator by Marat Fayzullin). After lots of calculations (see TWWMCA 9611.18 for details), I arrived at a color palette which I felt accurately represented what I saw on a TV set or NTSC color monitor. Here's what I got, compared to what Marat and Marcel used in their emulators:
==================================================
| | | RFD | MF & MdK |
| | =============================
| | | 8-bit value | 8-bit value |
| | TMS9118 =============================
| hex | color | R G B | R G B |
==================================================
| 0 | Transparent | 0 0 0 | 0 0 0 |
| 1 | Black | 0 0 0 | 0 0 0 |
| 2 | Medium Green | 71 183 59 | 32 192 32 |
| 3 | Light Green | 124 207 111 | 96 224 96 |
| 4 | Dark Blue | 93 78 255 | 32 32 224 |
| 5 | Light Blue | 128 114 255 | 64 96 224 |
| 6 | Dark Red | 182 98 71 | 160 32 32 |
| 7 | Cyan | 93 200 237 | 64 192 224 |
| 8 | Medium Red | 215 107 72 | 224 32 32 |
| 9 | Light Red | 251 143 108 | 224 96 96 |
| A | Dark Yellow | 195 205 65 | 192 192 32 |
| B | Light Yellow | 211 218 118 | 192 192 128 |
| C | Dark Green | 62 159 47 | 32 128 32 |
| D | Magenta | 182 100 199 | 192 64 160 |
| E | Grey | 204 204 204 | 160 160 160 |
| F | White | 255 255 255 | 224 224 224 |
==================================================
Marat saw a repost of my derivations on one of the USENET newsgroups (alt.folklore.computers), and insisted the RGB triplets he used in his color palette for the MSX2 emulators (which has a TMS9938 VDP, which has a backwards-compatibility mode with the TMS9918/28/29 VDP), was the actual RGB palette used by the hardware (determined either by some 9938 function call or from the 9938 Data Manual, he didn't say which). Marcel agreed with both of us: Marat was using the hardware palette, but mine looked just like what he saw on his composite color monitor.
Marcel told me that in AdamEm, his combined ADAM/ColecoVision emulator, he has included both palettes: mine is the default, but the "hardware" one is available as a startup option. How the same underlying "hardware" RGB palette can give rise to two totally different appearances on different display monitors (composite color versus VGA) must be due to the video modulator circuitry in composite monitors.
In any case, I'm glad that I worked through the math and derived the composite-color version of the palette. It's the one that I'm going to use in any image-conversion utility programs that I might develop (such as the one to convert PowerPaint 10K binary files to RGB TIFFs).
I still have a couple of old topics to clear out of my buffer, not the least of which is my "Mystery Man" interview. (I've even located a second "Mystery Man", and may have some information about who currently owns the rights to some of the ADAM software.) But after that, and after my review of the Telegames DYNA System (a ColecoVision-compatible game console), I will be free to take TWWMCA in any of a number of possible directions. Here are some options:
continue with the current porpourri, whatever happens to strike my fancy.
pick some topic of general interest, and systematically explore it (and eventually beat it to death). Such topics include: the internal workings of ADAMserve, or of the ColecoVision OS7 operating system, or a complete analysis of a ColecoVision game (like Pitfall).
pick some topic of interest to *me*, whether or not it's of interest to anybody else, and systematically explore it. Such topics include: trying to figure out what the Memory I/O Controller chip on the ADAM lower circuit board actually does (it interfaces the ADAMnet master 6801 and the Z80, manages memory bank switching, and controls dynamic RAM refresh, and probably more things), building an ADAMnet serial/parallel board that has working bidirectional serial I/O (the prototype serial/parallel can only send, it can't receive), or building an ADAMnet tape drive which can format new tapes (I believe it's possible).
use TWWMCA as a forum to publish important ADAM technical documents in electronic form, such as the ColecoVision Programmers Manual (including the Sound Users Manual and the Graphics Users Manual) and the ADAM Technical Manual set. Instead of writing new text for TWWMCA, I would be retyping existing documents from my collection. This would also be a place to document technical specs for various 3rd-party hardware (Eve, Orphanware, Micro Innovations, etc.) which are known (to me, anyway) only by disassembly.
anything else which I haven't thought of yet.
So, you, Gentle Readers, can help me choose the future direction of TWWMCA. I enjoy writing these articles; I would enjoy any of the things (1)-(5) that I suggested above. As I stated publicly at ADAMcon VIII, however, I want to use my time and efforts to the maximum benefit of the ADAM community. Since, by and large, my articles have not had the (intended) effect of generating conversation on the Coleco ADAM Mailing List, I am beginning to wonder if TWWMCA as I've been writing it is the right way to go.
Let's talk about this on the Mailing List (those of you who are subscribed to it, anyway; those of you who read TWWMCA through the reposts to alt.folklore.computers, comp.sys.misc, and comp.os.misc, you can send me E-mail).
See you next week!
*Rich*
Next Article
Previous Article
TWWMCA Archive Main Page