VBXE+U1MB --> MARIA/7800?

[Xebec]

Would it be technically possible for the VBXE board (combined with U1MB) with the right ROM / NVRAM bits to emulate the MARIA chip allowing the Atari 8bit to emulate/run 7800 games?

 

I understand a ton of work; just curious if it's even feasible without changing the boards hardware..    I assume GTIA isn't sufficiently backward compatible with TIA for sound?

[+Stephen]

It's the PoKey in the computers that does the sound.  Pretty sure it can be made to perfectly emulate TIA sounds.  The VBXE can certainly best the graphics, but as far as running a direct emulation layer, I doubt that would be possible.

 

phaeron did some pretty cool 2600 conversions a while back - I'm sure he would have much better insight into this.

[Xebec]

9 minutes ago, Stephen said:

It's the PoKey in the computers that does the sound.  Pretty sure it can be made to perfectly emulate TIA sounds.  The VBXE can certainly best the graphics, but as far as running a direct emulation layer, I doubt that would be possible.

True though I was also thinking the CTIA/GTIA chips are an evolution of TIA, and they do have a sound channel output -- sort of a 5th channel,  attached to the speaker on the Atari 400/800 and muxed to the output on the newer machines.  That *might* be directly compatible with TIA sound .. 

 

re: Graphics, VBXE is a FPGA so I was thinking if you reprogrammed the FPGA to simulate MARIA instead of ANTIC ..  though the architecture probably won't work, but I wanted to explore.  

 

Thanks..

[flashjazzcat]

3 minutes ago, Xebec said:

I was thinking if you reprogrammed the FPGA to simulate MARIA instead of ANTIC

The FPGA emulates GTIA, not ANTIC. Not sure if that's a help or a hindrance to what you have in mind.

[+DrVenkman]

While I'm sure MARIA could be reverse-engineered for an FPGA implementation, I don't think it has happened yet. And having said that, I'm pretty darn sure that working 7800's are still cheaper than a VBXE, let alone the combo of a working A8 machine + VBXE + U1MB.

[Rybags]

You can't emulate Maria but the versatility of the bitmapping (XDLs) and blitter can help.

7800 Display List Lists position objects in a sort of colour-clock mode which can translate easily to X coords on VBXE.

From memory with Moon Cresta I used 320 mode and a screen layout that was 512 bytes wide then just multiplied the XPos by 2 to get screen position on VBXE.

7800 has successive object scanlines 256 bytes apart which doesn't really suit - it's easier to just do sprite mapping in a more normal manner - in any case since you have 8bpp on VBXE there has to be changes anyhow.

 

If you have source code the job is a whole bunch easier - to port a game with a binary alone would be a whole lot more work.

 

C64 would IMO be an easier system to port from to VBXE - it's something I'd like to try sometime.