Maria on the A8?

[AtariNerd]

Something that has popped up in the 7800. programming forum. Sort of surmised this was possible, but still surprised to see it pop up. Looks like it is being accomplished by a PBI/ECI-cart add-on board.

 

In some ways it might seem redundant, given other options are available, like the VBXE, but since the base system share the same CPU, with the A8 having the POKEY already built-in, it seems like an interesting bridge between the two systems. 

 

I do wonder just how compatible the software is, though.

 

https://forums.atariage.com/topic/315966-my-experiments-with-atari-7800/?do=findComment&comment=5280442

 

Edited July 7, 2023 by AtariNerd
Added link

[+Stephen]

Thanks for posting that here - I had seen the link just a few hours prior - it sure came out of nowhere (at least to me)!

[+DrVenkman]

I'm not exactly sure what the point is here - isn't it easier (or wouldn't it be easier?) to just ... I dunno, buy a 7800? Rather than buying/building a custom MARIA carrier board to plug into an XL/XE computer? 

[Rybags]

Not sure how they are doing this - it looks like it's probably addressable and generating video locally.

Not a lot of point IMO for multilpe reasons.  VBXE is already here and not widely installed.  Maria stocks are probably not great, why disassemble a good 7800 to allow the computer to emulate it in some capacity?

Doing the Moon Cresta conversion - the graphics generation of the 7800 is somewhat different to just about everything, it's not text based or bitmap based, it's really just a sprite engine that's limited by available DMA per scanline to read the objects.  Generally converting a game involves going up a level or two from the hardware and just generating objects by translating the positional and data pointers.

I doubt the 7800 + Antic graphics could be combined easily.  Possibly something like an enhanced Sophia could take graphics from both and combine them.  But at the end of the day you'd end up with yet another graphics standard to support and I do suspect that porting games wouldn't be very direct.  In all probability the Asteroids might have been reassembled to cater for different addressing to the used hardware.  Additionally, you have TIA for the sound/controller inputs which is another consideration - likely games would need changes there as well.

[+mytek]

1 hour ago, DrVenkman said:

I'm not exactly sure what the point is here

35 minutes ago, Rybags said:

Not a lot of point IMO for multilpe reasons.  VBXE is already here and not widely installed.

The point is sometimes as simple as rising to the challenge of whether it's possible, and if so, to what extent. Why is there a VBXE? Why are there A8 emulators? What's the point if I can run stuff on the original hardware without these things. Why does Sophia have graphics modes that a stock GTIA chip doesn't, or for that matter a VBXE? We could question everything as to why someone would want to do this or that, but what's the point

 

To tell you the truth I always wondered if and when someone would combine a Maria chip with our A8 systems, and for what its worth I think it's cool 👍

 

BTW, I keep hearing people on this forum bemoaning the lack of support for VBXE, and then using that as a reason to not create or support new and different graphics enhancement devices. Bottom line is that just because the VBXE came before something else, doesn't make it the thing that everyone wants to get behind and support. As for lack of Maria chips to be had in the wild... look at what Simius did with the Sophia, or for that matter the creator of the VBXE. They both are based upon reproductions of no longer manufactured Atari VSLI chips with a twist. Why not also a combo Maria/GTIA in an FPGA    Could be very interesting indeed.

[+DrVenkman]

26 minutes ago, mytek said:

Why not also a combo Maria/GTIA in an FPGA    Could be very interesting indeed

Well, MISTer already does that, along with SALLY, RIOT and TIA (there’s apparently a pretty solid 7800 core design for MISTer enthusiasts). 

 

With NOS TIA’s going for $50 from Brad these days, the world is just about ready for an FPGA TIA replacement in a DIP40 form factor, if you ask me.  

[+mytek]

18 hours ago, DrVenkman said:

With NOS TIA’s going for $50 from Brad these days, the world is just about ready for an FPGA TIA replacement in a DIP40 form factor, if you ask me.  

Yeah I'm surprised that hasn't already happened. Or duplicate the single chip aspect of the later 2600 Jr.

 

18 hours ago, DrVenkman said:

Well, MISTer already does that, along with SALLY, RIOT and TIA (there’s apparently a pretty solid 7800 core design for MISTer enthusiasts). 

I still like the idea of being able to go either way, either with the real Atari VSLI chips or a drop-in replacement where possible. Although Mister and the Eclaire are very cool in their own right.

[Rybags]

Is TIA sufficiently reverse-engineered for a proper FPGA implementation?

I know that even in the early 80s competitors had their own versions but there's all those quirks that aren't necessarily replicated properly and games can not work as a result.

[Tickled_Pink]

7 hours ago, DrVenkman said:

Well, MISTer already does that, along with SALLY, RIOT and TIA (there’s apparently a pretty solid 7800 core design for MISTer enthusiasts). 

 

With NOS TIA’s going for $50 from Brad these days, the world is just about ready for an FPGA TIA replacement in a DIP40 form factor, if you ask me.  

Yeah, I'm surprised this hasn't happened yet either. Found out the other day that the Maria schematics are available online and was thinking that the TIA should be a much simpler device, so was wondering why nobody's done a drop-in replacement for either yet.

[+CharlieChaplin]

Forthcoming: VIC and SID on a PBI/ECI card. Wait, we already have SID available for the A8...

Coming next: Paula, Denise and Agnus on a PBI/ECI card.

And then: Tom and Jerry on a PBI/ECI card. And suddenly working Jaguars are not available anymore

 

 

[Rybags]

I wonder how the Ram interface would be done - I'm fairly sure the 7800 Ram is somewhat higher speed SRAM and accessed at 3.6 MHz effective?

So I guess it would have to have it's own dedicated Ram then the computer would need some way to also talk to it.  Maybe some sort of shadowing is going on where main Ram acts as a cache that the CPU has available then Maria has less impeded access to the SRam?

[+DrVenkman]

6 minutes ago, Rybags said:

I wonder how the Ram interface would be done - I'm fairly sure the 7800 Ram is somewhat higher speed SRAM and accessed at 3.6 MHz effective?

So I guess it would have to have its own dedicated Ram then the computer would need some way to also talk to it.  Maybe some sort of shadowing is going on where main Ram acts as a cache that the CPU has available then Maria has less impeded access to the SRam?

The 7800 architecture is weird - SALLY has the same 1.77/1.79MHz speed as it does in the A8’s, but it slows down to 1Mhz (I think? Maybe 1.19?) anytime TIA or RIOT are accessed. And since the controllers are accessed through those chips even in 7800 games, the system is always speeding up and slowing down, and then MARIA is tied to the video signal speeds … Scoping that system is hard to make a lot of sense of without knowing what’s going on. I would guess those SRAM chips were chosen by GCC to avoid trying to synchronize DRAM access speeds between parts of the system all sort of doing their own thing at their own rates. 

[Rybags]

Yeah, it's been a while since I looked it over.  Fair enough with RIOT/TIA since it's 2600 tech - the clock speed is colourburst/3 where A8/7800 is colourburst/2 on NTSC.

The Maria video accesses - I think it's something like 2 7.2 MHz cycles for RAM and 3 for ROM.  So you have to sit down and calculate how much bandwidth you have available for your graphics.

[+DrVenkman]

21 minutes ago, Rybags said:

Yeah, it's been a while since I looked it over.  Fair enough with RIOT/TIA since it's 2600 tech - the clock speed is colourburst/3 where A8/7800 is colourburst/2 on NTSC.

The Maria video accesses - I think it's something like 2 7.2 MHz cycles for RAM and 3 for ROM.  So you have to sit down and calculate how much bandwidth you have available for your graphics.

Yeah, I have never delved into 7800 programming at all, but I do casually follow the 7800 programming/development forum and see how those who know what they’re doing discuss the pros and cons of various MARIA modes and how much time they have for moving sprites, changing colors, memory access, etc. It’s astounding what some of those guys can do once they understand the system well. But the overall complexity + Atari Corp’s constant futzing with the hardware to make it cheaper to manufacture explains why hardware development for the system is so difficult - even the most-capable current-gen 7800 flash cart (the Dragonfly, no longer in production thanks to chip shortages) is not 100% compatible with every .A78 on every type of 7800 hardware. Concerto (still being manufactured) is even more hit-and-miss but at least Fred continues to work on firmware. 

[Eagle]

I don't want to go into too much detail, but it's like Super Maria  
It can make 3 times more sprites than the original Maria and is fully downward compatible. Except that it does not steal Sally cycles as it does in the A7800.
Can also display background in 320x200 resolution (each line can be scrolled independently)
Plus 8 covox channels (no Sally cycles usage)
and has 32MB on board 

7800 developers can easily adapt the code to work on the A8.

Edited July 8, 2023 by Eagle

[pirx]

we need Super Maria Sisters then

[Eagle]

YM2612+SN76489

 

 

[oky2000]

On 7/8/2023 at 7:53 AM, Rybags said:

Is TIA sufficiently reverse-engineered for a proper FPGA implementation?

I know that even in the early 80s competitors had their own versions but there's all those quirks that aren't necessarily replicated properly and games can not work as a result.

Apparently the Coleco Atari expansion #1 used discrete components so it's got to be fairly do-able. 

 

Like some others here I don't see the point, it's a bit like people who ripped out the BMW 220bhp engine from an M3 and replaced it with a 220hp Ford Sierra Cosworth engine. Law of diminishing returns and we already have VBXE as a bespokely coded for improvement to the A8 machines to juggle. This is the sort of thing you might do once, do a YT video about how you did it, and watch it go nowhere because it's an engineering challenge looking for a reason to exist in the world of retro-gaming really IMO. Interesting challenge though technically. Just spent a few days doing proper research about another early 8bit system that was hoping to get a shot in the arm in 1990 with some new abilities.

[Geister]

I may be talking crap here, but I've read that the VBXE's output is not compatible with many modern LCD computers, or something to that effect.  But then I have seen very little discussion about the VBXE other than that it's currently the only option for the b-bit computers.  So my question is if this upgrade has flaws, why the objection to alternatives?  In this thread I read that the Sophia makes new modes available to the 8-bit and I ask why have I never seen this before in discussions about the Sophia?  What new modes does it offer, I thought it was just to sharpen the output of the Atari composite display.

 

I want something that can produce 80 column displays and PC (EGA/VGA) like graphics and works with displays that aren't made of unobtanium.  That's why I'm very interested in Reifsnyder's 1090 revival as an expansion bus makes development of plug-in video cards feasible. 

[+MrFish]

18 hours ago, Geister said:

In this thread I read that the Sophia makes new modes available to the 8-bit and I ask why have I never seen this before in discussions about the Sophia?  What new modes does it offer, I thought it was just to sharpen the output of the Atari composite display.

It's been discussed and demonstrated since its inception (even a short video from the developer); but discussion has been minimal. The reason why is because the main focus and interest for the device is to provide better output for the standard video features of the machine; the extra features are just a bonus.

 

As far as I recall, the new features of Sophia amount to hi-res (graphics 8 / Antic F) where the pixels and background have their own colors (instead of just the normal 1 hue at 2 luminances). This is a long-time wanted/missing feature.

 

 

[Geister]

Thank you for that information. On many upgrades for the Atari, any new features or side features often do not get the highlighting they deserve.  Or, the information gets lost in the older threads.  Not all options get the exposure they deserve and by the time I hear of them they are no longer being produced by the original designer.

I think that it would be a good idea to add a pinned thread on hardware for the Atari 8-bits where designers can announce new hardware and provide documentation about the features of the new device instead of having a thread where somebody announces a device and takes orders then sinks into the old post to bit lost forever.  Sure, one could search for new hardware announcements assuming that there is a standard posting format that can be searched for, but how do you search for something elsewise if you don't know it exists?

 

Edited to add: If I'd known there were new features on the Sophia of that kind, I would have jumped on one long ago.

Edited August 20, 2023 by Geister

[+mytek]

17 hours ago, Geister said:

If I'd known there were new features on the Sophia of that kind, I would have jumped on one long ago.

I think it's good to point out that those extra features won't apply to any of the games and programs already out there that were written with the stock GTIA in mind. So in other words don't expect to pop in the Sophia and suddenly have more colors in existing applications.

[Geister]

Understood, but it's more to explore.  More to challenge myself with.  

I came back to the 8-bit because the PC architecture became too much for a single mind to encompass and the 8-bit world seemed a little smaller a friendlier, but I still want something new from time to time.  I just want the new stuff to be something I give a damn about, not what Microslth and the other big platforms want to shove down my throat.

The Atari 8-bit was damn near perfect but it should have achieved 80 columns and hi-res video modes  in a much more thoughtful manner than the kludge that Tratari flaccicly offered.  A well thought out expansion bus coud have provided that.  Witness how Apple had to deliberately hamstring and then kill off the IIGS because it made the Mac look weak by comparison. 

[tebe]

What other expansion has resulted in more than 100 new game titles.

 

MARIA ECI can make that happen.

 

[Rybags]

2 problems I see - lack of Maria chips and the fact you'd render a 7800 dead each time you harvested one.

The Atari could potentially become a peripheral, merely supplying joystick input and possibly uploading Rom images to the box but otherwise not participating or much benefitting from the experience.