Five monitors on a Commodore 128 [video]

https://www.youtube.com/watch?v=ul5hC3PY1Yg

by EvanAnderson • 1 month ago

136 36 1 month ago

Spoilers:

The trick was pretty easy to guess but still a lot of fun to see put into practice. The EGA monitor bits, and more broadly just the idea of trading color bit depth to multiplex signals for multiple monitors into a single framebuffer and physical output is pretty cool. The Windows display driver idea actually implemented on real hardware would be tons of fun. I could have seen products actually doing this "back in the day" to do multi-head setups. I'm kinda surprised examples don't exist.

badc0ffee2• 29 days ago

I think it's just that monitors were so much more expensive then, especially those capable of the 350-line EGA mode.

EvanAnderson2• 29 days ago

I'm sure that was a factor. As much as certain job roles today love multi-head (I'm particularly thinking head spreadsheet users) I could still have seen it being a possibility. Certainly, multi-head for AutoCAD was "a thing" pretty early, albeit the paradigm there was one monitor for graphics and another for text.

MBCook2• 29 days ago

Given you would have to do all the display stuff through bit math on the framebuffer I imagine interactive use would be horribly slow.

You could certainly use it to display other pages of a spreadsheet or something but I don’t think I’d want to type into a word processor that was doing it.

walrus01• 29 days ago

As I recall, some years later than this (referencing EGA monitors from the 80s), a 14 inch 1024x768 capable 75 Hz capable SVGA monitor with a reasonable dot pitch of 0.28, nothing special, something you might find bundled with a 386DX/40 or similar from a clone builder was something like $400 in 1992.

This would be the inflation adjusted equivalent of $970 today.

So basically like buying a really nice super high refresh rate 32" gaming display.

jchw2• 29 days ago

Since everyone is vibe coding everything anyway I fully expect there to be a Windows 3.x display driver that works this way soon. I'm sure people in the retro computing hobby feel a certain way about this, but it's definitely also hard to deny the amount of "Project Structure" in README and "// ---- Input Handling ---------------------------------------------" snippets I've been seeing lately in a lot of new homebrew and other projects. (Another fun one: comments that are justified to a specific column but off by one in only one of them. I'm sure humans do this too, but AI does it more.) I don't really care that much personally although it's silly that people kind of have to be wink-wink-nudge-nudge about it for the foreseeable future.

TacticalCoder• 29 days ago

Yes what's with that in LLM output?

It used to be a big thing in the nineties: I've got old .asm source code of mine where I used to do that.

But somehow LLMs love to insert dashes everywhere: dashes in source code an em-dashes in prose. Just why?

Did they parse lots of early code and thought it was cool to insert, in modern programming languages, comment lines full of dashes?

Another fun one: comments that are justified to a specific column but off by one in only one of them.

Oh yes, all the time. And besides the fact that there are the off-by-ones errors, it of course looks horrible in Claude Code CLI seen that what you see is not what the LLM did output (because they vibe-coded their "real time game engine" that changes characters, for no reason, on the fly).

It's 2026 and we've got "intelligent" machines doing this:

    //  -------------------------
    // ------------------------
    // ----- Input Handling ----
    //  ------------------------
    //  |--------------+-------+------|
    //  | Potentiometer |  Min | Max | 
    //  |--------------+-------+------|

Which they'll probably "fix" by adding the following vibe-coded tool, of course hidden in their pipeline:

    ascii_table_to_unicode_mismatch_alignment_fixer(...);

What an era.

utopcell2• 29 days ago

"Every mathematician wants to discover a mathematician's lemma."

It might have been easy to guess, but you didn't really think of it in the past 51 years since the Commodore 128 was introduced, did you?

myrandomcomment• 29 days ago

The C128 was introduced in January 1985 at the CES in Las Vegas, so 41 year. Read your post and thought, "I am not that old!"

I went from a VIC20 to C64 then to a C128D in 1987. Then moved a 486DX50 running OS/2 in 1990.

HerbManic• 29 days ago

Would be the kind of product you see demoed on The Computer chronicles from Eagle New Global Tech corporation, you gander at it thinking "Wow, one day I will get that" and then you never hear from the company again as they only sold 4,000 units.

So like most of the gadgets from the 90s.

twh270• 29 days ago

Back in the VGA days, I worked for a video card maker, and one of them supported a multi-head configuration. You could stick as many as 16 into one machine, if it had enough slots. Thus driving 16 monitors at once. I was responsible for taking the stock Windows 3.1 display driver for the chipset and modifying it for multi-head support. That was a really fun and challenging project, and ultimately very satisfying. I am pretty sure there were a few customers who needed the full 16-card setup.

BTW this was done in the day when drawing pixels on a screen was all done via the CPU telling the card "draw /this/ pixel with /this/ color". Good times!

econ• 29 days ago

Could you accomplish something similar with just colored foil? Like, red foil makes red and white look the same.

jerf• 29 days ago

It is unclear what you are asking. What you are asking sounds more like using something to add color to the monochrome on the screen, like the Magnavox Odyssey [1] or the Vectrex [2]. But that would be orthogonal to what this is doing.

[1] https://youtu.be/Lc8swrtGer4?t=211

[2] https://www.youtube.com/watch?v=uz3QAj7I3MQ

pavon• 29 days ago

I think they mean that rather than have the RGBI splitter hardware, have a full-signal splitter that displays the same full color image on each monitor, then put a color filter sheet on each monitor to only pass a specific color.

It would have the benefit of working with NTSC, PAL, composite, and other output signals that don't breakout RGBI components on separate pins. But it would have the downside of only supporting 3 monitors instead of 4 (can't color filter on intensity). And of course each monitor would look red, green, or blue according to their filter.

rzzzt• 29 days ago

You could generate sweet stereoscopic images with two differently colored foils placed in an eyeglasses frame: https://en.wikipedia.org/wiki/Anaglyph_3D

forinti• 29 days ago

I started seeing LED displays on store fronts in the late 80s (the ones that scroll text horizontally).

This would have been quite the product then. TVs were expensive, but B&W TVs not so much.

mixmastamyk• 28 days ago

Hmm, some clarity would be lost going through the TV tuner, but probably worth the price difference.

gfdgfdff• 29 days ago

Oh him. Is the loser still appearing on camera with his gun? What a douche.

ddtaylor2• 29 days ago

I'm so confused.

freegum7772• 29 days ago

He started making videos on youtube about 8bit computers, then weirdly started appearing on camera with a gun during them, and then a bunch of stuff surfaced about his views/comments in this area.

That's probably normal in Texas, not so much in the rest of the world. It comes across as a very nerdy, softly-spoken guy trying to come across as a tough guy.

It's very odd (like I said, especially to an international audience - I subscribed to him, then dropped him like a hammer when he started with the gun crap).

Search him and add the word "gun", you'll see some of the history.

ddtaylor2• 29 days ago

Thanks for sharing. I have been enjoying Davids content for many years and hope he keeps making awesome stuff. The Time Rift Arcade has been neat too.

bhouston• 29 days ago

You could use the hot lines from RBG as the binary id (2^3) of the monitor and then average up the RBG intensity from the hot lines as the result. This would give you 8 monitor support.

Or you could limit it to 3 monitors but two hot lines pick the monitor and then you can sum the intensity on those two hot lines two double your fidelity.

If you do the two line color system you could have a YC signal of luminance (Y) and chrominance (C) and thus you have a color signal.

zahidullah2• 28 days ago

hiiiii

Five monitors on a Commodore 128 [video]

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