Any plan for RGB mod for C64 and 128 in 64 mode?

[7800fan]

C64 and the 128 in 64 mode uses VIA to output video and they are capable of only Y/C and composite. Is there any information around of an add on board or a drop in replacement chip that can output RGB signal?

[Rybags]

There is none that I know of. But there's a cartridge that emulates what VIC-2 does and outputs RGB.

 

Turbo Chameleon 64 http://www.syntiac.com/chameleon.html

 

Does VGA output and more like REU, Turbo CPU, disk drive emulation and emulation of freezer/action replay cartridges.

Seems it can also be used standalone as a C64 system emulator, just supply power and plug in a PS2 keyboard.

Edited April 16, 2015 by Rybags

[carlsson]

For comparison, I've learned there is a reasonably new NES RGB mod that does not require a PPU from a V/S system. I haven't looked into exactly what it does or which signals are available from the PPU to tap, but I doubt the VIC-II internally works with RGB anyway. The Turbo Chameleon might be kind of an answer, otherwise you would need some sort of replacement VIC-II chip or daughterboard that generates a compatible signal. I don't think that is easy.

 

The French back in the 80's supposedly installed Y/C splitters to get RVB into the C64, but the signal quality from the splitter board according to my source made the picture worse than if you had used Y/C. It is possible there are better Y/C splitters today, could be worth looking into if you are hard pressed for RGB output.

 

If you feel lucky, you could also try a composite and S-Video upscaler to HDMI, but your milage might vary by a great deal what the outcome is, in particular as the C64 outputs higher voltages than what you'd normally expect from S-Video. There are mods to bring down the levels though, might be advicable.

 

http://www.ebay.com/itm/400309329713

(currently $40 + shipping)

Edited April 16, 2015 by carlsson

[Rybags]

C64 would be harder than e.g. Atari to do a "proper" RGB video output based at a low level on what the video chip is outputting.

 

C64 only has Colour and Sync/Luma pins. Atari supplies Colour, seperate CSync and 4 Luma pins which would make the job easier.

Also C64 allows colour change at hires pixel equivalence which would make decoding which colour is in effect harder.

Possibly the best solution is as exists - just snoop the bus and emulate what you think the real thing is doing.

[carlsson]

FWIW, can the C64DTV be modded to output RGB? ISTR it only has composite on the outside, but that isn't to say it wouldn't be capable of other. I didn't yet research the topic, and even if it would handle RGB, a heavily modified C64DTV still isn't the exact same thing as a real C64, even if emulation is splendid.

[+OLD CS1]

Be careful with those composite/S-Video to VGA converters.

 

A couple of threads detailing our woes in TI land:

 

http://atariage.com/forums/topic/233051-using-composite-to-vga-converters

http://atariage.com/forums/topic/172937-getting-s-video-from-the-ti-console

 

A couple of specific posts:

 

http://atariage.com/forums/topic/172937-getting-s-video-from-the-ti-console/?p=2146377

http://atariage.com/forums/topic/172937-getting-s-video-from-the-ti-console/?p=2819013

 

 

tl;dr: Many of our platforms from the 80s output progressive video rather than interlace. The cheaper converters expect interlaced video.

[Greg2600]

Probably would have to be something like the RGB mod boards made for NES, which are very expensive.

[Timstuff]

Sorry to bump such an old thread but has anyone talked to Tim Worthington about the possibility of an RGB kit for the Commodore 64, like he's done with the Atari 2600 and the NES? I own both of those boards and installed them into my systems and it was like magic when I saw the difference. Given that the reason the C64 can't do RGB is due to the PPU itself only outputting composite, in theory an RGB board with a "helper chip" that bypasses the PPU and creates its own RGB signal would be the ideal solution.

 

I am just a modder and not an engineer though so I don't really know the technical difficulties involved with designing a board like that, let alone making one that can be installed in all the revisions of the C64 (and hopefully the 128 as well). I also don't know if Tim Worthington has any interest in retro computers or if he doesn't think it'd be worth his time.

[carlsson]

The VIC-II outputs Y/C actually, and I believe it internally works with that colour model too.

 

The NES RGB mod consists of a board that sits between the motherboard and the PPU, capturing colour info and then combines with the image signal from the PPU. Does the NES have a shared memory bus just like the C64, or does the CPU feed all data to the PPU all the time? I'm not an engineer as well, but I would suppose the fact the VIC-II shares the memory bus with the CPU and generates the display without getting fed with data makes a difference.

 

Rather I think we'd need a solution like the F18A for the VDP systems, a FPGA implementation of the graphics processor. There exists one or more cores of the VIC-II of varying degree of compatibility. We'll see how well Gidjeon's Ultimate 64 will work out, and if he's interested in producing a VIC-II replacement chip similar to what the SwinSID does for the SID chip.

[Timstuff]

It's possible that a solution could incorporate the original chip in some capacity (the NES and VCS boards involve removing the original chip from the motherboard and placing it in a socket on the RGB board). It may be more convenient to completely replace the VIC2 like with the SwinSID though, as you mentioned. There is more than one version of the VIC2 and it might be a hindrance to have to design a board around them all, when the alternative is just to have a jumper on the RGB board for the VIC2 it's replacing-- as well as the fact that the replacement chip would likely generate a lot less heat, and would be great for the C64s out there with dead or dying VIC2 chips.

 

It'd be great to hear from someone who actually knows more. My C64 looks great when plugged in to a 1702 monitor, but with the framemeister it doesn't hold up quite so well-- especially since I have one of the older breadbins with the older VIC2 chip.

[TMR]

Does the NES have a shared memory bus just like the C64, or does the CPU feed all data to the PPU all the time?

Neither if memory serves, looking through my old prototype code it all seems to all be writing to the PPU and display RAM through a port - writing appears to use two stores to $2006 which set the high/low of the address and $2007 writes data - rather than accessing either directly.

[carlsson]

But it is your program that does these writes, so it goes through the CPU every now and then? Obviously the CPU is involved when it comes to defining various bits of the C64 graphics too, but I think the approach technically is different.

 

In any case, there surely are enough C64 users in the world to make a RGB solution worthwhile if it is possible to achieve, so anyone looking to make a buck or two probably already have looked into it but come to the conclusion it is a different kind of problem to tackle.

[TMR]

But it is your program that does these writes, so it goes through the CPU every now and then?

The program writes to the port but the CPU doesn't directly touch the screen RAM or registers, so setting up the palette might look like this...

 

; Set palette address for copying
		lda #$3f
		sta $2006
		lda #$00
		sta $2006

		ldx #$00
load_pal	lda tile_palette,x
		sta $2007
		inx
		cpx #$20
		bne load_pal

...and after that's done once the PPU fetches the palette from it's own RAM without the CPU getting involved - you did ask if the CPU was feeding "all data to the PPU all the time"...

[White Flame]

RGB doesn't exist anywhere in the C64, but if you're looking for a chip replacement that does RGB output, then you might look at something like the Turbo Chameleon 64. It reimplements the VIC-II chip in FPGA, and simply plugs into the expansion port, snooping the bus. It outputs VGA. However, they're between revisions and out of stock until the next one comes out.

 

Other than that, you're going to be stuck converting the existing Y/C to RGB.

Edited February 28, 2018 by White Flame

[carlsson]

Or one could pre-order the Ultimate64 motherboard at 209 Euros. It has a FPGA implementation of the VIC-II and will output HDMI.

https://ultimate64.com/Ultimate-64

 

Personally I'm totally fine with Y/C output, no need for RGB/VGA for my C64.

[TMR]

Personally I'm totally fine with Y/C output, no need for RGB/VGA for my C64.

i'd like VGA because i take machines to retro gaming events and the stock of HP L1706 monitors i have is far easier to deal with than CRTs... but i have MyGica Gamebox HD upscalers for those gigs which are reasonable and a TC on my main work machine.

[carlsson]

I've got two Samsung LW15M23C which are fine for me to carry, though one did get a few scratches last time I brought it inside a suitcase.

[Zap!]

If there's anyone I would like to see try and answer these questions, it would be AA user Simius. He created the amazing Atari 8-bit RGB mod called Sophia.

[carlsson]

Does the GTIA have its dedicated memory, is raw data sent from the ANTIC subsystem for GTIA to generate the picture (similar to how a 6845 is used in other systems)? I don't know the Atari hardware that well, but I think the VIC-II is more of an integrated solution: reading the same memory shared by the CPU - thus the badlines, generating the image based on all the data it reads, generating the display as Y/C video with an internal palette model. If it was made up of two chips, one composing the image and one generating the actual video, I'm sure there would be internal RGB solutions for the C64 by now.

 

External converters from composite or S-Video to HDMI (which I suppose is the new black after RGB) already exist and do their job with various degrees of quality. Then again both the TC64 and Ultimate 64 in their FPGA implementations of the VIC-II chip so far have their issues, not everything is implemented/emulated as expected, so it is a bit like plague or cholera if you insist of using any other type of display than one that handles 15 kHz. You'll spend an awful lot of money and either get lag or bugs while you really were looking for a very cheap solution that works 100% from day 1.