DLOAD "80 COLUMN RGBI CABLE FOR THE C128"
I was going through my back-issues of Loadstar disk magazine, which I have on compact disc, when I came across a really interesting article on the first issue of Loadstar for the Commodore 128. It was an article on how to make your own RGBI video cable out of a standard RCA cable, so you can utilize the 128’s eighty column mode without having to have an RGB compatible monitor.
The article (see below) goes on to explain that the drawback to using the 80 column mode this way is that you bypass the RGB signal and are only accessing the 80 column monochrome channel. So, all you are left with are three colours: black, white and gray. Anything in colour is translated into these three so-called colours. The article gives a detailed table of how these colours are translated.
It then goes on and provides you with a parts list of what you will need to make this cable, along with Radio Shack SKU numbers for these parts, as well as their prices (back in the day). You are even given a diagram as to which pins to use, on the DB-9 connector.
So, with this information, I decided to make one of these cables for myself.
The only DB-9 connector I had was this breakout board style connector. But it should work well to test things out. If this cable works well, I can make up something more permanent later.
The RCA cable I used was just your standard cable you'd use to hook up your video signal (from your DVD, VCR or whatever player) to the video cable on the back of your T.V. - the yellow plug cable. I cut one end of the yellow RCA plug off and stripped the casing back to expose the two smaller wires inside. There's a “center” signal wire and an “outside” ground wire.
I proceeded to connect my RCA cable, as described in the article (center wire to pin 7 and ground wire to pin 1 or 2) and then taped everything up with electrical tape. Then, I plugged the 9 pin DIN end into my 128 and the yellow RCA plug into my RCA/S-video to VGA converter box, which then plugged into my VGA monitor via it's VGA output. If this works, it will be the first time in a long time, that I get to run my 128 in 80 column mode. I was really hoping the results were good.
And, wouldn’t you know it, the signal on my LCD monitor was clean and quite sharp. It looked better than what I expected it to be. The display would have been even sharper, if I were using an RGB monitor, but the composite signal still produced text that I could easily read. Of course, the real benefits of 80 column mode come into play when using software specifically written for the extra wide screen. Like DraCopy, for example. I much prefer the side-by-side interface, in 80 column mode, when compared to the top-bottom interface in standard mode.
But, what about the issue with everything in monochrome? So far, it’s only been a minor annoyance in games. For example, BurgerWhop. This is one of my favorite 128 games, but it’s only playable in 80 column mode. It looks great, but some of the burger ingredients are black, which makes them invisible on the black screen. A minor annoyance for, what I consider to be, the best version of Burger Time available on the Commodore 64 or 128, which I could only play on an emulator, until now.
However, gaming wasn’t the main reason why I wanted to utilize 80 column mode, on my 128. It’s the applications that I wanted to run, which I couldn’t do before; applications like GEOS. GEOS, for the most part, is a monochrome application. So, it looks perfectly fine in 80 column mode, with this RCA cable. I’m quite confident that most of the other business applications, for the 128, will also look just fine in monochrome.
I did come across a couple of issues (colour-wise) with applications published in Loadstar 128, like MasterFile II. However, they were easily fixed by changing a few lines in the BASIC code. That's one of the nice things about software in Loadstar: for the most part, they publish software in such a way that you can easily examine and tinker with the code.
It is really surprising at how important a resource Loadstar was for the average Commodore user, back in the day, before there was the Internet. I’m finding that there is quite a bit of useful information, even for today, locked away in it’s electronic pages.
459 visitors.
The Loadstar Cable Article
HOW TO MAKE A C128 80-COLUMN CABLE
by Edward J. Corr
You've got your Commodore 128 up and running. BASIC 7.0 is great; and you've found interesting 128 and CP/M software, both commercial and public domain. And now you're wondering about 80-column mode. Would you like it? Would it be truly better in some applications? Do you have to buy a $300 RGB monitor to find out?
Not necessarily.
“Would you believe…” you can find out for only about $7.00, and a little work on your part. If you can solder, or have a friend who will do that small chore for you, you can easily check out 80-column mode. All you need is a video cable that can access it and a standard, NTSC Composite-input monitor. Sorry, a TV won't work here unless it also has direct video input; or unless it's hooked up to a video cassete recorder (VCR) that will take auxilliary video input. But that's another article in itself.
What you will achieve with the help of this special cable is a monochrome (black and white) version of the 80-column screen. The only limitation this causes is in the selection of colors. With the monochrome arrangement, you can have three screen colors: black, white, and gray. This can work just fine as long as your software has made the right choices, or gives you the option to make changes to all assigned colors. Otherwise some screen messages, images, etc. may become invisible when normally different colors translate into the same color as your monochrome background color.
Let me explain. The C-128 puts out 16 different colors on the 80-column RGB “color” screen. The 80- column “monochrome” screen has three color choices. Somehow 16 colors must be squeezed down to three. That means that five or six different RGB colors can come out as the same color in monochrome. The translation table appears on the next page:
RGB Color Monochrome Color
1. BLACK BLACK 2. WHITE WHITE 3. DARK RED GRAY 4. LIGHT CYAN WHITE 5. LIGHT PURPLE WHITE 6. DARK GREEN GRAY 7. DARK BLUE GRAY 8. LIGHT YELLOW WHITE 9. DARK PURPLE GRAY 10. DARK YELLOW GRAY 11. LIGHT RED WHITE 12. DARK CYAN GRAY 13. MEDIUM GRAY BLACK 14. LIGHT GREEN WHITE 15. LIGHT BLUE WHITE 16. LIGHT GRAY GRAY
For example, your background color is white and a screen message gets printed in light purple. Since both of these translate to white in monochrome, they both end up the same color, and the message is now invisible - like the proverbial black cat in the coal bin. The message, like the cat, is still there. You just can't see it since it's now the identical color as its surroundings (white letters on a white background).
But, except for this particular problem, there's no reason why you can't use your non-RGB monitor for 80-column programs. Here's what you do.
All of the following parts are available from various sources. Radio Shack part numbers (P/N) and prices are given only as a universal reference. Where you get these things makes little difference. The only item where quality can vary considerable is the cable; don't try to save pennies here unless you're very sure of what you are getting.
1 each DB-9 Male Connector
P/N 276-1537 $1.49
1 each DB-9 Connector Hood
P/N 276-1539 $1.99
1 each Cable, RCA - RCA, 6'
P/N 42-2367 $2.19
NOTE ABOUT RCA - RCA CABLE:
We will be cutting off one end of this cable. If you already have good quality shielded cable, by all means use it. I suggest that you keep the cable four to five feet long; I find three feet too limiting. Just be sure it has FULL braid, not the new/cheap junk that is only partially covered by braided shielding. You will also need the RCA plug for one end (such as the Radio Shack P/N 274-383 or 274-319 or 274-451 packages). For the best image results, you may even substitute 75 ohm video cable. Just be aware that you will give up quite a bit of cable flexibility, which may be important on a cramped desk top.
INSTRUCTIONS
1. Prepare the Cable. If you are using an RCA-to-RCA cable, simply cut off one of the connectors and strip back the insulation, exposing the center conductor and the shield. If you're using bulk cable, go ahead and solder on the RCA connector, center conductor to center pin, shield to connector barrel. Now go ahead and strip back the other end of the cable.
2. Add the DB-9 Connector. Time to solder on the DB-9 connector. Solder the center conductor of the cable to Pin 7 of the connector. Solder the shield braid to either Pin 1 or 2 of the connector, whichever is convenient for you. You can even solder it to both pins, they're tied together inside the C-128 anyway.
3. Check Your Work. Double check the solder joints, especially the DB-9 pins. If you used Pins 2 and 7, add insulation between them (a piece of electrical tape, sleeving, RTV, etc.). Consider adding insulation even if you used Pins 1 and 7; a cable occasionally gets pushed back into its connector. If too much wire was exposed by stripping, it could bend over and short to other pins.
4. Add the Hood to the Connector. Please don't eliminate this step, it would be false economy.
5. Install. Plug the cable into the RGBI Connector port at the back of the C-128 (reference page 649 of the System Guide), plug the cable's RCA connector into the Composite Video Input jack on whatever monitor you're using. Push down the “40/80 DISPLAY” key on your C-128 keyboard and hit the RESET switch, or simply hit the “ESC” key and then “x” if you're already in 40-column mode.
6. Adjust The Monitor. You may have to adjust your monitor for best display. This is definitely true if you're using a color monitor. When you have an 80 character wide display, that's 640 dots (pixels) that the screen has to be able to show along each horizontal line. And it should show them clearly enough for you to distinguish each separate dot. That's really pushing the capabilities of some color monitors. (Standard, inexpensive monochrome monitors should have no problem showing these dots; they actually work best for this particular application. But go ahead and try the available adjustments anyway.)
The adjustments that you are most concerned about are: Sharpness or Focus, Brightness or Intensity, and Contrast. Color-specific adjustments such as Tint, Hue, etc. will generally not be critical; experiment with them last. Sharpness, Brightness, and Contrast all interact; when you change one, the others usually have to be changed also. We want to get the best, clearest display that your monitor is capable of. Here's the key.
Turn DOWN the Contrast (usually Counter-Clockwise) as far as you can, and still see something on your screen. Turn UP Brightness (Clockwise?) to compensate. If your screen suddenly starts to expand or “balloon” in all directions, back off the Brightness a bit. Twiddle with these two controls until you get your best image. Just remember, if you have a choice, turn Contrast DOWN and Brightness UP.
Now adjust Sharpness for the clearest dot patterns. Try to get the individual dots that make up each letter and character on the screen. Readjust Contrast and Brightness as needed. When you're satisfied that these are set the best they can be, then it's time to experiment with changes to Hue, Tint, etc.
7. Sound. Don't throw away your 40-column video cable yet! If you want sound, you still need that cable, so leave it plugged in at the back of the computer. Assuming that your monochrome monitor has a SOUND input jack/connector, plug in the proper wire from the cable to that input. If the cable has several plugs (usually of different colors) and you don't know which one is sound, don't worry. Just try each plug in the monitor, the wrong one won't hurt anything; it simply won't give the proper sound.
If you get unusual noise or humming, that's the wrong plug; try another one. With no program running, you shouldn't hear anything through the monitor's speaker. When you think you've got it, run any sound-producing program as a final test. If the program produces sound continuously, go ahead and swap plugs while it's running until you hear what you expect. (Tip: Mark that wire/plug as your sound source, even if just by wrapping a piece of masking tape around it and writing AUDIO or SOUND on that.)
8. ENJOY! Just remember that what you now have is a monochrome, black and white, version of the 80-column screen. And if you decide you like it, just wait until you see 80 columns in full color!
EDITOR'S NOTE: The chart on page 5 of this text is something that all 128 programmers should be aware of. If you are writing programs for public consumption, make sure your color scheme will work in 80-column monochrome mode.