Graphics Accelerator Chip for VIC-20

[RJBowman]

I've been reading up on graphics enhancements included on cartridges for consoles; specifically the Display Processor Chip on the Pitfall II cartridge for the Atari 2600 and the Super FX chip that provided polygon rendering for Star Fox and a few other Super Nintendo games.

Has anyone tried to make a graphics accelerator for the VIC? I imagine that these days this could be done with an off-the-shelf microcontroller. I know that cartridges are not a popular media for hobbyists' games, but this might be a worthwhile thing.

What kind of features would be worth putting into it?

[Mike]

Recently, we had a similar discussion about hardware assisted games here on Denial: link.

[olafL66]

Unfortunately the VIC chip cannot reach memory in the cartridge port, and the cartridge cannot reach memory or the VIC chip.

Only the C64 had DMA capability to fill memory from a cartridge, so you could create a blitter that does the calculations to change the bytes in graphics memory for lines, filled squares and (filled) circles which would be faster then pure 6502 coding.

If you wanted to add better graphics and faster drawing on a VIC20, you could add a Videochip in the cartridge and put that output to a monitor.
That was done before with a 40/80 character cartridge with mono video out (for sharpness to normal b/w TVs).

[Mike]

Unfortunately the VIC chip cannot reach memory in the cartridge port, and the cartridge cannot reach memory or the VIC chip.

Yeah, that's one of the things that inspired me to create the VFLI mod on my VIC-20 in 2010.

Only the C64 had DMA capability to fill memory from a cartridge, so you could create a blitter that does the calculations to change the bytes in graphics memory for lines, filled squares and (filled) circles which would be faster then pure 6502 coding.

Even without hardware assist I have a fast line routine at my disposal that does 30000 pixels/second (yes, you read that right: thirty thousand) and likewise, fast circle/ellipse routines (~4000 pixels/s) and fast fills (flood fill or geometry fills for polygons/circles). At that speed, graphics primitives aren't that much of a bottleneck anymore. You also need a fast geometry engine for those routines (doing translation/rotation/projection in 2D or 3D space), otherwise the speed of the graphics primitives is gobbled up in the surrounding overhead.

Anyhow, some people in the forum here struggle at much simpler problems than implementing routines for (bitmapped) graphics.

There are also some other people here, who think beefing up the(ir) VIC-20 with extra hardware (besides RAM expansions or modern mass storage solutions) and/or a new OS would be the cure-all to their problems.

I won't go as far as to imply there's a certain overlap between those two groups, but ...

If you wanted to add better graphics and faster drawing on a VIC20, you could add a Videochip in the cartridge and put that output to a monitor. That was done before with a 40/80 character cartridge with mono video out (for sharpness to normal b/w TVs).

Providing the VIC-20 with a mostly text-oriented extra video hardware to allow for sensible word processing with 40 or 80 columns is fair enough. Even though, with little problems, a purely software-based 40 column mode (with fairly readable 4x8 pixel characters) is feasible.

If you put a new graphics video chip into the cartridge port, though, then there's not much left of the VIC-20. You could quite as well use a C64 (or any later contemporary 8-bit machine) instead. IMO.

[darkatx]

Anyhow, some people in the forum here struggle at much simpler problems than implementing routines for (bitmapped) graphics.

Guilty as charged!

[bdk6]

If you put a new graphics video chip into the cartridge port, though, then there's not much left of the VIC-20. .

Everyone has their own opinion on these things, but I agree with that statement. For me, much of the appeal is the minimalist systems we had 35 years ago and making the most of them. It's a challenge. Or a puzzle. I've often been tempted to build all sorts of fancy add-ons for my VIC (and some other old computers) but I always come back to "then it wouldn't be a VIC 20."

[cbmeeks]

If you put a new graphics video chip into the cartridge port, though, then there's not much left of the VIC-20. .

Everyone has their own opinion on these things, but I agree with that statement. For me, much of the appeal is the minimalist systems we had 35 years ago and making the most of them. It's a challenge. Or a puzzle. I've often been tempted to build all sorts of fancy add-ons for my VIC (and some other old computers) but I always come back to "then it wouldn't be a VIC 20."

Agreed. With the exception that if the video enhancement provides a way to ditch CRT's in favor of VGA or HDMI. I love CRT's (I have many of them) but they are a pain sometimes.

One great example is the F18a (TMS9918 replacement). Although it goes a little overboard in features, you don't have to use them. At its core it's a cycle-accurate, drop-in replacement for the TMS9918 but with VGA output. I wished the VIC had something similar.

[bdk6]

provides a way to ditch CRT's in favor of VGA or HDMI.

To my way of thinking that would be great. Composite inputs / CRTs are getting more and more difficult to find. Making the output compatible to displays that are actually available wouldn't change the character of the machine at all, really. But it would keep it usable a lot longer. You can even get boxes on ebay for a few dollars that will convert a composite signal to VGA or whatever. It would be nice if someone created a VIC replacement with VGA output.

[siccoyote]

I agree if you want a vic with graphic and sound enhancements you may as well just use a c64.

The appeal for me is the Vic as a relic from a certain point in time and seeing the things that could have been possible if people knew then what they know now.

I'm not even sure why I'm more obsessed with the vic than the c64. It's not even nostalgia, I was a speccy kid.

As people have said if you put too much new stuff in it it's not the original article anymore like the ship of Theseus.

[cbmeeks]

I'm not even sure why I'm more obsessed with the vic than the c64. It's not even nostalgia, I was a speccy kid.

That's understandable...to me anyway.

I think the VIC-20 and the Speccy are similar in a lot of ways.

(/me runs and hides....)