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Is a new ANTIC in CPLD feasible?


Larry
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VBXE duplicates what GTIA does though (the video part).

 

Antic... it's probably a case of why, but in concert with an improved GTIA replacement things could get interesting.

 

Most of the time the A8 is using half or less of the available memory bandwidth to generate video, so we could in theory do an upward compatible system with some better graphics mode.

Think stuff like...

 

GTIA bitmap modes with all 256 colours 80 pixels width.

16 colours instead of 4 for the hires multicolour (160x) bitmap mode.

4 colours for hires (320) mode.

Like VBXE, eliminate the annoying single colour/2 luma limitation of hires modes.

Character modes allowing 256 definitions instead of 128.

Attribute memory, either dedicated or loadable by DMA.

 

Of course most of this stuff would mean incompatability issues and yet another set of video capabilities to support.

 

Another thing to consider - DMA based audio, blitter and maybe even peripheral I/O. With a custom Antic, spare cycles could be put to use.

Maybe even add stuff like TIA and Maria partial emulation.

Edited by Rybags
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If anyone was to enhance the Antic, certainly would try to do 2x,4x HOZ mode, Double and Quadruple the internal clock frequency. I am sure there are unused bits in the registers or map another 16 registers in the $D4xx area. Is $D406 and $D408 used for anything?

Edited by peteym5
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The trick would be to have compatibility mode as default and use an unlock bit somewhere to put it in enhanced mode.

Then have the extra registers just map into spare space in the $D4xx page.

 

Another enhancement could be more/better PMGs. Maybe even C64 style sprites instead.

Just do the extra DMA like Maria does it - leave it to the programmer to ensure enough cycles exist to do what's required. Missed DMAs can just reuse whatever data was already there.

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If anyone was to enhance the Antic, certainly would try to do 2x,4x HOZ mode, Double and Quadruple the internal clock frequency. I am sure there are unused bits in the registers or map another 16 registers in the $D4xx area. Is $D406 and $D408 used for anything?

 

Just guessing/speculating.... What ANTIC does is defined by the speed of the entire system. It does what it does based on the DMA time available in the system. Things that a superdeedooperdee ANTIC would do that need more DMA would probably need the entire system, bus, and memory running 2x or 4x or more times faster in order to provide the necessary data/DMA time.

 

At that point we have an Amiga. :-) (not that that's a bad thing ).

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Just guessing/speculating.... What ANTIC does is defined by the speed of the entire system. It does what it does based on the DMA time available in the system. Things that a superdeedooperdee ANTIC would do that need more DMA would probably need the entire system, bus, and memory running 2x or 4x or more times faster in order to provide the necessary data/DMA time.

 

At that point we have an Amiga. :-) (not that that's a bad thing ).

I would imagine a faster chip would just have an internal clock subdivided to give the higher throughput. I think it could work that way, similar to how the hi-res mode is really a hack.

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What ANTIC does is defined by the speed of the entire system. It does what it does based on the DMA time available in the system. Things that a superdeedooperdee ANTIC would do that need more DMA would probably need the entire system, bus, and memory running 2x or 4x or more times faster in order to provide the necessary data/DMA time.

 

Well, it all depends on the price and complexity of that Hyper Antic.

 

Some things indeed depend a lot on the available bandwidth. Both system bandwidth, and the bandwidth of the private ANTIC-GTIA bus. But a lot of things could be done internally without any external modification. You could use internal ram to store players graphics, no need to consume system bandwidth.

 

And, if you want to pay the price and use an FPGA, not just a CPLD, well ... you could snoop the bus and keep a shadow of the whole system RAM if you want ...

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Antic... it's probably a case of why, but in concert with an improved GTIA replacement things could get interesting.

 

 

GTIA bitmap modes with all 256 colours 80 pixels width.

16 colours instead of 4 for the hires multicolour (160x) bitmap mode.

First, a technical comment. The limitation why (non-GTIA) modes are limited to four colors is that Antic and GTIA communicate only by three lines, i.e. only 3 bits are available to transport playfield data from Antic to GTIA. Thus, replacing ANTIC alone does not give you more colors in the playfield, unless you also upgrade GTIA. With the current ANTIC-GTIA interface, you are limited to five playfield colors. (Yes, really five, not four).

 

Then, maybe a more general comment on this: I wonder a bit what the purpose of this exercise is. I mean, after all, you do not get any additional software by such a feature, and the 8-bits are certainly completely outdated systems, so if you want more colors, buy an Amiga (for a considerably similar system) or a PC (for a system with many more features).

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WIth enhanced Antic/GTIA I would think doing it in a single package would be desirable. As such the AN0-AN2 lines become internal and somewhat irrelevant.

 

Throw 80-col mode into the mix too.

Though the problem is, the expense would probably approach what a VBXE costs, which brings into question the reasoning for making it.

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Antic+GTIA in one single package (without enhancements) - Atari made it, named it CGIA and later Keri and never released it. But Curt Vendel once posted a list with more of those unreleased Atari chip designs...

 

http://www.atariage.com/forums/index.php?showtopic=74377&hl=Rainbow

or:

http://www.atarihq.com/danb/AtariChips.shtml

 

quote "Keri was an Antic/GTIA/Pokey combined, Meg was a Cmos version of Pokey, Porkey was a stereo Pokey, Misty, MTV, Star and a few others I have not determined as of yet..."

Edited by CharlieChaplin
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