Can you Mod an SG-1000 and Colecovision like an NES for RGB?

Started by panzeroceania, February 15, 2011, 04:50:14 PM

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panzeroceania

What I mean is, the only mods I see for the SG-1000 or Colecovision are not for RGB. I am assuming this is because the usual ICs in them don't support RGB. I was wondering if anyone has tried to swap out the ICs with one's from other systems like the SC-3000, Coleco Adam, MSX etc. like you can switch the IC from a PlayChoice into an NES or Famicom.

If so could are there any tutorials out there? Is this possible?

Midori

SG-1000 and Colecovision uses a TMS 9918 for video, you should be able to swap this for a TMS-9928 instead(not sure actually if Colecovision already uses a 9928). Although 9928 does not output RGB, but you can build a circut to convert the YUV colours to RGB for the 9928 and then you get RGB.

You might also be able to use a V9938 or V9948 instead, they have real RGB outputs but require a large operation and I'm not sure if you can actually do it, even if they are software compatible.


skforty

One caveat though;

Its been said that most of these french versions of these consoles that are exclusive in outputting RGB (like the linked secam COLECO) are actually X-to-RGB hacks, and not TRUE RGB.

http://www.assemblergames.com/forums/showthread.php?t=28318

"The French were lucky mainly due to the French government deciding to have a completely different TV standard to the rest of the world, PAL improves on NTSC and it is not that difficult to change a composite signal into either PAL or NTSC, SECAM on the other hand requires a little more hardware.

A lot of the RGB mods were Composite or similar to RGB which was simpler to do then trying to output a SECAM signal, so the RGB offered isn't 100% crystal clear. The french Atari 2600 did output SECAM and offered a total of 8 colours where as PAL offer 96 and NTSC 128... "



That said, who cares.  Its gotta look better than composite and probably VERY good and much easier than the alternatives...


NFG

I was looking at getting one of these French NES systems a long time ago, but when I found out it was a regular old NES with a composite->RGB converter inside I lost interest.  The only thing you'll save in this configuration is a little bit of quality normally lost on the cabling to the TV. 

Midori

Shouldn't a modern TV actually handle the composite to RGB conversion even better than the Sony chip from the 80s(In the NES case)? Logic says yes but I have nothing that says that it can be wrong too.

panzeroceania

February 17, 2011, 03:55:19 PM #6 Last Edit: February 17, 2011, 04:01:00 PM by panzeroceania
Yes I also read about the French Colecovision but figured it must be a stock Colecovision with RGB converter. I completely forgot about the Adam though. That's probably the route I'll take if it does indeed output true RGB.

I have another question for you guys. Has anyone considered making a unified list of what the internal ICs of all consoles output from the bare board? for example, some consoles output RGB, while some, like the NES, just output composite, While others, like the early atari consoles output Chroma and Luma.

a list with pics of the ICs with labels would be amazing, I know there are some out there like the atari 2600 mod page on the wiki, but it'd be cool if there was one uniform place that showed them all.

Example from the wiki:



panzeroceania

February 17, 2011, 05:26:32 PM #8 Last Edit: February 17, 2011, 06:40:10 PM by panzeroceania
I'm sorry lawrence, you must think I have several mental deficiencies by now.

thank you. thank you very much.

EDIT:

what is this VGA cable tapping? it can't be RGB. Is is just YPbPr?

http://www.goldenshop.com.hk/AI-trad/gc/vgacable.htm

NFG

Well, as you can see from the GameCube digital pinout spits out digital component.  There's a chip in the component cable that converts it to either analogue component, or RGB. 

panzeroceania

Good to hear, I guess I'll pick one up then if it's truly digital to analog RGB source and not digital > YPbPr > RGB

bigsanta

Quote from: Midori on February 16, 2011, 04:12:58 AM
SG-1000 and Colecovision uses a TMS 9918 for video, you should be able to swap this for a TMS-9928 instead(not sure actually if Colecovision already uses a 9928). Although 9928 does not output RGB, but you can build a circut to convert the YUV colours to RGB for the 9928 and then you get RGB.

I'm definitely trying this out !

ApolloBoy

Quote from: bigsanta on February 23, 2011, 06:04:44 AM
Quote from: Midori on February 16, 2011, 04:12:58 AM
SG-1000 and Colecovision uses a TMS 9918 for video, you should be able to swap this for a TMS-9928 instead(not sure actually if Colecovision already uses a 9928). Although 9928 does not output RGB, but you can build a circut to convert the YUV colours to RGB for the 9928 and then you get RGB.

I'm definitely trying this out !
I figured I'd necro this as I'm in the middle of doing this with my SG-1000 II right now. If you're going to swap out the 9918 with a 9928, you actually have to build a circuit for the system clock. The 9918 outputs the 3.58 MHz signal required for the Z80 and SN76489, and unfortunately the 9928 doesn't, so if you just do a straight swap the system won't boot. Thankfully both the SG-1000 II and original SG-1000 have spots on the board for the system clock circuit so you just need to add a 3.58 MHz crystal, 74HC04 inverter (and it needs to be the HC version) and a few resistors and caps. I'd like to give thanks to TmEE on SMS Power for helping me figure this out!

Also, the ColecoVision already has the 9928 so no need to do a swap. If you're not interested in component you can swap it with the 9918 and get composite video.