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Tandy (1000) Video II, Mode E - 640x200x16

Cloudschatze

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I mentioned this in the Yahoo! Tandy1000 group, but, for the benefit of anyone who may not subscribe...

The Tandy Video II chip, first introduced with the TL/SL in 1988, has a hi-res, 640x200x16 graphics mode that was largely ignored. Two game titles I'm aware of that do make use of it are Interplay's "Star Trek: 25th Anniversary," and "Mario Teaches Typing." I'd love to know if anyone knows of any other examples.

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Were these games ported over from the Apple IIGS? Because I know in the IIGS's 640x200 mode, you have to do that weird kind of vertical striped shading effect in order to get all the colors on the screen, but on a Tandy, it shouldn't be necessary.
 
The discussion on yahoo group is being very enjoyable! Delightful and NICE!

Such a interesting information to share.

Thanks!
 
Were these games ported over from the Apple IIGS? Because I know in the IIGS's 640x200 mode, you have to do that weird kind of vertical striped shading effect in order to get all the colors on the screen, but on a Tandy, it shouldn't be necessary.
Nope, neither of those were IIGS games; they were both available on DOS and Mac, and Star Trek had an Amiga port. On the IIGS there's some funky hardware restrictions on which colors can appear in which columns in 640x200 mode; these titles appear to simply be using it as easy dithering to simulate more colors at a perceived 320x200 (which was their native resolution anyway.)
 
Here are a handful of supporting titles from The Learning Company, who, interestingly enough, referred to this specific graphics mode as "ETGA."

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Treasure Cove!


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Time Riders in American History


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Treasure MathStorm!


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Math Rabbit Deluxe
 
What great art all this is. I'm kind of bummed I don't have a compatible Tandy. I have a TX and a 2500SX, doh. Guess that's one more reason for me to pick up a TL at some point.
 
Makes sense that most were educational games, because Tandys were big in schools. And I'm sure with the CM-5 monitor's huge dot pitch, the hi-res dithering becomes invisible and the image truly appears to have more than 16 colors!
 
I'm sure with the CM-5 monitor's huge dot pitch, the hi-res dithering becomes invisible and the image truly appears to have more than 16 colors!

I'd recommend using at least a CM-11 for the 640x200x16 mode. The CM-5 exhibits some pretty horrible moiré patterning at this resolution.

There's a palette of 256K possible colors (blended), according to TL technical reference manual. Not too shabby...
 
I'm interested in how they figure that, given that there's only 256 possible 16-color pixel pairs, and 112 of them are mirrors of identical pairs. Unless they're factoring in some Apple II-style NTSC color bleed or something...
 
It's likely just some sort of typo.

So, different question. Has anyone ever looked into creating some sort of software routine that would effectively "map" the Tandy's 320x200x16 and 640x200x16 video modes to their EGA counterparts (and then appear as such to supporting software)?
 
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The problem with that is that EGA is planar while TGA is chunky (and EGA is straight framebuffer while Tandy below 640x200x16 interleaves lines.) You can write conversion software for that, but it's not fast. Furthermore, the EGA includes a handful of simple accelerator hardware (masked, shifted writes and such) that the TGA doesn't. It'd be easier and more performant to just hack up TGA rendering code for the individual programs.
 
Unless they're factoring in some Apple II-style NTSC color bleed or something...
Not possible - the TL doesn't have composite video out, does it? Even if it did, this technique would only get you a maximum of 64K colors, not 256K (NTSC's color resolution is 1/4th the pixel clock in 640x200 mode, so 4 conscutive pixels will blend into a solid color, and each of these has 16 possible values). Still pretty impressive if it was possible.
 
I dunno about the TL, I know my RL doesn't have composite output. I'm guessing either they just screwed it up, or there's been some mistake and this actually refers to the VGA Tandy PCs (VGA having 6-bit DACs for each color element, totalling 256K possible colors.)
 
So, different question. Has anyone ever looked into creating some sort of software routine that would effectively "map" the Tandy's 320x200x16 and 640x200x16 video modes to their EGA counterparts (and then appear as such to supporting software)?

If you're looking for some sort of TSR to do this -- meaning, allow EGA graphics programs to run transparently on TGA systems -- this is impossible without a 386 to run programs in V86 mode so their memory and port reads/writes can be trapped and massaged.

The routine has been written before, if you just want to see how to do it. Graeme Devine's Turbo Champions does this; the internal bitmap is created as 160x200 in CGA/TGA's interlaced format and then blown to the screen with REP MOVSW for those modes; for EGA, he wrote a routine that blows the same bitmap into EGA planar memory (at a noticable speed penalty). You'd have to run in DOSBOX's debugging mode to trap/watch it, or try to disassemble it. I might try to disassemble it because I want to see how his scaling routines work (I know how they work by looking at their output, but am curious how he used the registers).
 
That looks fantastic. I just happen to have my tandy 1000 Tl sitting right here. I was always a fan of this video mode but nothing other than deskmate seemed to use it. I believe Gif converter or something named similarily like that (an image display program) support this mode. I used use it for displaying some pretty great looking pics on the tandy 1000tl

I'm going to try out these titles today on the system. Anymore suggestions. Star trek looks fantasic. I had this on the system as the time but I recall it running much too slow to be playable.

What I need is a sierra graphics driver to take advantage of this mode. I wonder maybe it already exists for kings quest V.
 
What I need is a sierra graphics driver to take advantage of this mode.

Sierra never made a 640x200x16 Tandy driver, that I'm aware of. Someone could certainly create one though...

Such a driver would make the following Sierra SCI1.1 titles "playable" on a stock, TGAII-bearing system (all of which feature PSSJ DAC and "3-voice" music support besides). Per the Wikipedia list:

1992 Christmas Card
EcoQuest: The Search for Cetus
EcoQuest II: Lost Secret of the Rainforest
Freddy Pharkas: Frontier Pharmacist
The Island of Dr. Brain
King's Quest VI: Heir Today, Gone Tomorrow
Laura Bow: The Dagger of Amon Ra
Leisure Suit Larry 6: Shape Up or Slip Out! (disk and low-res CD-ROM version)
Mixed-Up Mother Goose (Version 2.000)
Pepper's Adventures in Time
Police Quest: In Pursuit of the Death Angel (enhanced remake)
Quest for Glory I: So You Want to Be a Hero (256 color remake)
Quest for Glory III: Wages of War
Space Quest IV: Roger Wilco and the Time Rippers (CD-ROM version)
Space Quest V: The Next Mutation
 
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