Magnavox Odyssey 2: 64 Shapes?

[BladeJunker]

I've been looking over the oldest school game systems to see what they can do graphically, one such system is the Magnavox Odyssey2.

 

I found all the sprite performance basics under the Wikipedia page but haven't had any luck with what all 64 shapes or characters look like? I also can't find an approximation of the 16 system colors listed anywhere either.

 

Even if I deduct 26 letters and 10 numerals I still have 28 8 by 8 pixel characters unaccounted for. Anybody know of a level editor or someone who's exported the data from the MO2 ROM or something? Even if I manually extract from every screenshot I can get my hands on it would be a lot of work and I could still miss one.

 

Any place you know of where I could ask even would be most appreciated as my searches haven't found a heck of a lot?

[jeremiahjt]

Any place you know of where I could ask even would be most appreciated as my searches haven't found a heck of a lot?

 

MagnavoxAge.com.

 

All kidding aside I have never come across a site dedicated to the Odyssey2. I would even hazard a guess that this site might hold the largest collection of Odyssey2 fans you can find.

Edited June 15, 2012 by jeremiahjt

[GroovyBee]

All kidding aside I have never come across a site dedicated to the Odyssey2.

 

Have you tried http://www.videopac.nl ?

 

I would even hazard a guess that this site might hold the largest collection of Odyssey2 fans you can find.

 

Not as many as are on the forums on the site I linked to .

[desiv]

There are several good sites, but you'll probably need to look for videopac.

Dan Boris' site has lots of great info, including an awesome pdf.

http://www.atarihq.com/danb/o2.shtml#techfiles

 

It has a color list and character map description.

(Not with actual images of the characters tho, more descriptions).

 

desiv

[BladeJunker]

MagnavoxAge.com.

Hah good one, actually this domain is still up for grabs it would appear.

[BladeJunker]

Have you tried http://www.videopac.nl ?

 

Not as many as are on the forums on the site I linked to .

Ah right Videopac, didn't try that, such an odd name imo. This looks pretty good, thanks you.

[BladeJunker]

There are several good sites, but you'll probably need to look for videopac.

Dan Boris' site has lots of great info, including an awesome pdf.

http://www.atarihq.c...shtml#techfiles

 

It has a color list and character map description.

(Not with actual images of the characters tho, more descriptions).

 

desiv

Well I'm sure I can find it somewhere if I try Videopac, thanks for the link.

[+atari2600land]

There's also this: http://www.the-nextlevel.com/odyssey2/

 

But I think what you're looking for may be this:

http://home.kpn.nl/~rene_g7400/vp_info/G7000_symbols.gif

[BladeJunker]

There's also this: http://www.the-nextlevel.com/odyssey2/

 

But I think what you're looking for may be this:

http://home.kpn.nl/~...000_symbols.gif

Another link thanks, I don't have a MO2/VP but its on my list and fun to learn about in the mean time.

 

Yep that's the 64 or 63 it looks like shapes I was looking for. Its surprising since I didn't expect some of them to be so specific like the people and boats, I thought for sure those would have been custom sprites. Well its not quite ANSI/ASCII level but I see how they would fit together to make a number of games.

 

Thank you very much.

[BladeJunker]

I found the colors too or at least some people trying to reverse engineer the RGB values.

 

http://videopac.nl/forum/index.php?topic=1631.0

[Jess Ragan]

The whole notion behind the Odyssey2's built-in character set is that if they built the sprites into the machine, they could cut corners everywhere else. That worked pretty well for Magnavox for about a year, until licensed arcade games with distinctive mascots demanded more than the Odyssey's handful of robots and abstract shapes.

 

On the plus side, I can't recall a single Ody2 game that had any flicker in it. The machine could push around a lot of objects at once, provided they were all boulders and pale robots.

[Hatta]

The whole notion behind the Odyssey2's built-in character set is that if they built the sprites into the machine, they could cut corners everywhere else.

 

If you look at 0x32-35 it looks like the O2 doesn't even flip these sprites in hardware. That's really cutting corners!

 

On the plus side, I can't recall a single Ody2 game that had any flicker in it. The machine could push around a lot of objects at once, provided they were all boulders and pale robots.

 

True. The smoothness of O2 graphics even leaves a favorable impression today.

[Phredreeke]

A few games, Frogger and Backgammon comes to mind, updated sprite registers mid-screen to achieve a larger number of sprites. The catch is that timing is different between NTSC and PAL units, so such a game would run on either PAL or NTSC, but not both, unless you make a second version for the other system.

[Rolo]

I may be a bit late, but I just found this thread.

A character table of all predefined characters, together with their exact bitmaps, can be found in the Appendix of the manual of Videopac 9 "Computer Programmer".

Do you still need it?

[Flojomojo]

There's also this: http://www.the-nextlevel.com/odyssey2/

 

But I think what you're looking for may be this:

http://home.kpn.nl/~rene_g7400/vp_info/G7000_symbols.gif

THANK YOU for finding that, I was looking for that same image (I think it might be from the Computer Intro manual?) but could not find it anywhere.

 

I wanted to use it as a background someplace. Now I wish I could remember why I wanted it. IT'S SO BEAUTIFUL

 

[CatPix]

A few games, Frogger and Backgammon comes to mind, updated sprite registers mid-screen to achieve a larger number of sprites. The catch is that timing is different between NTSC and PAL units, so such a game would run on either PAL or NTSC, but not both, unless you make a second version for the other system.

The second catch is that unlike almsot every other systems, the video is generated differently, to my understanding, the game "picture" is realized internally as a whole complete picture then this pciture is sent to the video chip to be turned into a 240p signal. This make classic video based tricks harder to do since the system doesn't allow you to change something by line to make it flicker at 60 htz and add colors to a sprite, for example.

 

On the other hand, it mean that the video was less prone to flickering AND that the timing issues between PAL and NTSC machines are less important - the biggest issue is that the games had to be reprogrammed for the different resolution, but there isn't any speed difference between a PAL and a NTSC game.

 

The whole notion behind the Odyssey2's built-in character set is that if they built the sprites into the machine, they could cut corners everywhere else. That worked pretty well for Magnavox for about a year, until licensed arcade games with distinctive mascots demanded more than the Odyssey's handful of robots and abstract shapes.

Let's recall too that the Videopac is powered by a microcontroller, which is a stripped down microprocessor. The Intel microcontroller used in the Videopac was used for example in pocket calculators, in remote controls in the 90's, in home automation control panels, etc...

As you can guess it's not exactly a powerhouse, so using build-in items meant that the controller had less job to do. It's interesting to note that the Videopac also include a rando number generator and a maze generator, which is why you have several of those games on the machine, because they were quite easiy to make.

 

Using built-in items also mean that you have less things to write : smaller ROMs are possible : cheaper carts : more profit.

Edited October 21, 2016 by CatPix

[samscud]

I realize this is an old thread, but it's still showing up for searches so here's some info...

 

The second catch is that unlike almsot every other systems, the video is generated differently, to my understanding, the game "picture" is realized internally as a whole complete picture then this pciture is sent to the video chip to be turned into a 240p signal. This make classic video based tricks harder to do since the system doesn't allow you to change something by line to make it flicker at 60 htz and add colors to a sprite, for example.

 

The O2 actually generates the image on the fly, so you can alter registers halfway through a field to have more than 4 sprites + 28 characters simultaneously on the screen. You just have to make sure you have enough time to update and the data. The 8048 in the O2 runs at 1.79Mhz, which is further divided by 5 "states" for a one byte instruction, or 10 "states" for a two-byte instruction. This works out as between 179,000 and 358,000 instructions per second. This seems like a lot, but (for NTSC) when you divide this by 59.94 (field rate), you have at most 5,972 instructions per field or 22.75 instructions per scanline, and 443 instructions during vertical blanking.

 

The 8244 VDC can control several objects and helps reduce to load on the processor. It will output signals for background color, grid color and position, the 4 sprite colors and 28 (4 x 4 quads + 12 individual) characters that are in it's memory.

 

To change info in the 8244 VDC (video display controller), you have to enable it onto the bus (you would do that in vertical blanking); then you have to turn off graphics to update them; you need to copy the new data over to the VDC byte by byte; and finally need to reenable the graphics again. This will take longer than one scanline. To reposition a sprite, you will need to update 3 bytes (assuming you don't change the bitmap) per sprite. The hardware has a special "copy EXTERNAL RAM to VDC" mode, where the following sequence uses 8 instruction cycles per byte copied from RAM to VDC:

LOOP:

MOVX A,@R0 ;reads from external ram

MOVX @R1,A; writes to VDC

DEC R0

INC R1

DJNZ R2,LOOP

Just copying three bytes takes 24 instruction cycles (longer than a scanline). You could save a few instruction cycles by not using a loop. The following code takes 18 instruction cycles instead of 24 (although it uses 12 bytes of memory instead of 6):

MOVX A,@R0

MOVX @R1,A

DEC R0

INC R1

MOVX A,@R0

MOVX @R1,A

DEC R0

INC R1

MOVX A,@R0

MOVX @R1,A

DEC R0

INC R1

 

To see if a game uses these "mid-screen update tricks", just hold the RESET button down on an actual console. This will halt the 8048 as long as you're holding the button down, and stop any VDC updates. Since the 8244 continues to generate the video signal, you can see what is actually in the VDC memory. If half the on screen objects disappear, you'll know that updates are ocurring.

I think the source of your misconception might be because the O2EM emulator caches parts of the screen to speed up screen updates, and this is why some games (Wall Street, Frogger) have problems running correctly.