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Racing the Beam: The Atari Video Computer System


Albert

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Mr. Decuir,

 

Have you seen any of the new stuff being developed for the 800/XL/XE? Stuff like this:

 

 

or demos like this:

 

 

 

 

 

 

 

Additionally, one hopes that the following multi system emulator that is in the works (link below) will emulate some if not all Mr. Decuir's creations/designs

 

http://www.techradar.com/news/gaming/uk-un...emulator-528487

 

what would be nice would be an all in one hardware emulator that mimics/emulate all of atari's hardware platforms (incl. coin op)...perhaps Joe Decuir could assist in the design of that system

 

Going back to Mr Decuir's last comments, I guess the reason why cbm didn't go down the videogame (with the lorraine/amiga thing) route is simply because they (cbm) didn't want what would have been a souped up Max/Ultimax system that cbm would have had to have sold at a loss just to get it on the market...and also because they could see that market was heading into the toilet so they switched gears and worked on computer based applications for that hardware

 

Just curious as to whether Mr. Decuir ever got to see the proposed atari version (worked on under the warners admin) of the lorraine/amiga chip set or didn't it get past the drawing board stage (chipset only, not the actual system)

hello,

I saw the demos. Someone is having fun.

 

CBM kicked out the Tremiel clan in early 1984, then bought Amiga in mid-1984.

They were entranced by the MAC (which came out in January 1984) and decided to morph the Amiga into a color MAC.

They were not long on vision. Nintendo was.

The Amiga chipset was conceived to be able to render cartoon animation in real time.

Depending on how much detail you wanted, it could.

 

Before that sale (to CBM) Amiga peddled its chipset to Atari for coin-op use ONLY.

That didn't end in a product. Atari itself failed, to be dismembered and sold off.

The Tramiel clan bought the consumer part, and tried to get the Amiga chipset.

Only the lawyers benefited from that dispute.

 

BTW, you can call me Joe.

 

yours,

 

Joe Decuir

 

 

As Atari800 coder since 1986 I have to admit that I love Antic and it's display list concept... I found the concept very flexible and creative plus even later when touching Amiga, Atari7800 or even PSX.

 

as partly involved in Numen... have a look here, too:

 

;)

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Heya Joe, good to see you getting involved here. Hope all is well since the last time we talked.

 

Before that sale (to CBM) Amiga peddled its chipset to Atari for coin-op use ONLY.

 

The problem is, we know now that is not the case thanks to all the documents Curt uncovered. In return for the initial investment, Atari would get a one-year exclusive use of the Amiga design as a video game console. After the year, Atari was allowed to add a keyboard and market the complete "Amiga computer" setup, designated as the 1850XLD and codenamed "Minnie".

 

The Tramiel clan bought the consumer part, and tried to get the Amiga chipset.

 

Unfortunately, that's half the story it turns out and even then only subterfuge on their part - the Tramiel's never planned the ST around the Amiga chipset. That was a lawsuit launched to counter Commodore's initial lawsuit and injunction against Tramiel launched immediately after the announcement of him buying Consumer. When they bought Consumer, they had no idea about the Atari-Amiga deal and first discovered it during the end of July when they were evaluating programs, personel, documents, etc. (which I believe you told me is when you left again).

Edited by wgungfu
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Great information, Supercat! thanks. :)

 

Would the use of the 40-pin Mos6502 have increased the number of registers available to programmers?-how many does it have?

 

How many registers does the Mos6507 have, for comparison?

 

I know I've read somewhere here, probably Nukey, that if the VCS had just one more register(for a certain function?) that it would have increased it's abilities in at least one significant way.

 

I'm just curious, and unfortunately don't know enough about the VCS to even know if I'm making sense.

There are different kinds of "registers" on the Atari 2600.

 

The 6507 CPU chip has six registers-- A (the accumulator), X (one of two indexes), Y (the other of two indexes), P (the program counter), S (the stack), and PS (the processor status flags).

 

The 6532 RIOT chip has several registers, related to input, output, and the interval timer.

 

And the TIA chip has numerous read and write registers, related to the Atari's graphics and sounds.

 

I'm pretty sure Nukey was referring to the TIA registers.

 

Michael

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Review:

 

I quite enjoyed the book. The earlier chapters were better than the later chapters. Towards the end, the authors seemed to have lost their focus, particularly during the Empire Strikes Back chapter, where the topic of conversation changes repeatedly without any real rhyme or reason. That chapter started out very promising, and then just fell apart into a discussion of a bunch of unrelated topics.

 

Still a good read. Solid B

 

-Howie

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Review:

 

I quite enjoyed the book. The earlier chapters were better than the later chapters. Towards the end, the authors seemed to have lost their focus, particularly during the Empire Strikes Back chapter, where the topic of conversation changes repeatedly without any real rhyme or reason. That chapter started out very promising, and then just fell apart into a discussion of a bunch of unrelated topics.

 

Still a good read. Solid B

 

-Howie

 

 

That's exactly what I found.

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  • 2 weeks later...

Nice, but:

If you've ever seen little black lines appear at the left edge of the screen while you're playing a VCS game, those are bits of the game's code where the program is taking too much time doing other calculations, and it can't draw on the screen, leaving it blank. The black bar on the left-hand side of the Pitfall! screen at top was Activision designers' solution -- they cut out part of the gameplay field in exchange for more processing time.

Sorry, but this is completely wrong.

 

The black bars come from repositioning sprites (it is the hardware, not the "program"), they are hard to avoid. Activision decided to hide them by making the left border completely blank, which costed (not gained!) them some CPU time.

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The black bars come from repositioning sprites (it is the hardware, not the "program"), they are hard to avoid. Activision decided to hide them by making the left border completely blank, which costed (not gained!) them some CPU time.

How do you know this?

The first is well documented, the 2nd comes from disassembling the ROM.

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The black bars come from repositioning sprites (it is the hardware, not the "program"), they are hard to avoid. Activision decided to hide them by making the left border completely blank, which costed (not gained!) them some CPU time.

How do you know this?

The first is well documented, the 2nd comes from disassembling the ROM.

So where'd the other info come from then? (the incorrect one)

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Ah ok. So the book is right then.

 

Not quite. The Atari 2600's horizontal motion circuitry is rather complex, and I doubt that more than a handful of people back in the day ever understood it (and I suspect none understood all its wrinkles). The horizontal motion circuitry is designed to hit each sprite with 0 to 15 extra motion pulses during horizontal blanking interval. That would have the effect of moving the sprite 0 to 15 pixels left. To allow sprites to move rightward, the TIA designers engineered the TIA so that an HMOVE would blank the first 8 pixels of the following line and disable the motion pulses that would normally occur there. Eliminating the first eight motion pulses effectively moved all the sprites eight pixels rightward. If the horizontal motion registers were set to output 8 pulses, the 8 pulses they output would offset the eight pulses that were blanked, leaving the sprite's position unaffected. If it output fewer than eight pulses, the sprite would move right. If more than eight pulses, it would move left.

 

There are two ways to reposition objects without blanking the left 8 pixels of the following scan line:

 

-1- Set the sprite's position to a multiple of three pixels using RESxx and don't fine-position it with HMxx/HMOVE. For shapes that are at most six pixels wide, one may achieve pixel-level control by selecting one of three different versions of the sprite shape. Both approaches were used back in the day, but I don't know if they were ever combined (the only use I'm aware of for the latter is in Galaxian).

 

-2- Hit the HMOVE register just before the start of horizontal blanking. This will trigger the pulser circuitry for the usual 0-15 pulses, but it will not trigger the blanking circuit for the next line. The net effect is that sprites will move 0-15 pixels left (instead of -8 to +7) but the HMOVE "bar" will be eliminated. I am unaware of any game using this technique in the twentieth century.

Edited by supercat
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Finished the book this week. Great read. I am always amazed that others love this system as much as I/we do. I never thought of it in the terms of a platform study like this and the book is well organized; unlike the actual events that unfolded in the early 80's. I don't think it gets into off-topics, as I feel its written more like an ethnography of the console (if there could be such a thing).

 

Enjoyed it very much. Would recommend to others, even if they were not die-hard 2600 fans. Some technical lingo but I think it frames "why" the 2600 is different than other systems/platforms.

 

CN

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