Full Color Graphics in DOS on a DEC Rainbow!

The Rainbow is a bit of a misnomer in that out of the box, it isn’t actually capable of color graphics. However, there was a color graphics card available for the machine, and it just so happens this machine has one installed. But, color graphics do us no good if the monitor is purely monochrome. Enter the Princeton Ultrasync. Let’s see if we can hook this unknown monitor up to DEC Rainbow and get some colors going!
For more information on the Rainbow pinout, check out these links:
www.larosse.net/pc100/VR241.html
www.larosse.net/pc100/dec100-...
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Intro Music adapted from:
Artist: The Runaway Five
Title: The Shinra Shuffle
ocremix.org/remix/OCR01847
Thanks for watching!
Chapters
0:00 Rainbow? More like Monochomebow, amiright!
4:26 Our comparison program
5:57 The Princeton Ultrasync
8:48 Reverse Engineering the DB25 pinout
11:50 Building the cable
13:27 Let’s give it a test
14:33 Can you use a computer blind? Sure!
16:48 Testing it proper
18:51 Nothing is ever this easy, but I’ll take it!
20:52 Koma-san!

[@Taras-Nabad]

We really owe a lot of credit to DEC for pioneering much of the technology used today.

[@chrissingleton6029]

I couldn't agree more!!

[@manuell3505]

Historic high-quality stuff like IBM and Sun.

[@scottlarson1548]

Can you be specific?

[@LP6_yt]

This all really takes me back. As an old-timey IT guy I get all nostalgic at the sight of this wonderful gear. You just get a whole different set of issues arising from kit like this compared to today.

[@edgeeffect]

Oooh... seeing MS-DOS smooth scroll like it's on a VT100 is truly a sight to behold! Thinking of DOS graphics demos, my first question would be "FRACTINT?" I like to use old salvaged electrolytics in my projects just to troll the obsessive recappers.

[@idahofur]

I could tell just looking at the monitor and something in the back of my head told me that monitor probably supported just about everything back then. Nice clear monitor too.

[@mattsword41]

"roll with it, we're making films, we're having fun" - love it 😂😂

[@SammyRenard]

To think that a computer that struggled to draw lines and fill colors was still extremely expensive makes me glad that home computers have gotten so powerful since

[@kuglepen64]

That smooth scrolling gets me every time.

[@ygrella]

My very first computer was a Rainbow 100 ! It came with CP/M only and had an amber display, but it was fitted with the double-height 10MB Winchester hard drive! I really wish I didn't throw it away when it stopped working. Now thirty years later, I would probably have been able to repair it :) Aaaah, this smooth scrolling...

[@vinhtran9308]

The NEC µPD7220 is a true Graphics Processor, capable of drawing primitives such as lines, circles, fonts and even bliting. Such things did not show up in PC compatibles until 1987 with the IBM 8514.

[@richardwang9315]

FYI, that same NEC μPD7220 Graphics IC was also used in a Japanese 16 bit home computer, the NEC PC-9801 (First model of the First generation PC-9800 series, abbreviated as the PC-98). Which, (on later models) were known for Anime styled games such as Visual novels, Touhou, etc

[@semicuriosity257]

1984-era IBM PGA supports 640 × 480 with 256 colors which includes an on-board Intel 8088 CPU. The secondary 8088 ran software routines such as "draw polygon" and "fill area" from an on-board 64 KB ROM so that the host CPU didn't need to load and run these routines itself. PGC supports 640 × 480 with 256 colors from a palette of 4,096 and registers compatible with CGA.

[@binarydinosaurs]

As someone who's used DEC stuff his entire working life and was part of 90s DEC for a while, this warms my cockles, Need to fix my 'bow 100B+ after it expired earlier in the year whilst on display at a retro event. The VR241 also works with an Amiga500 :D

[@T3hBeowulf]

I worked in QA with a gentleman who used to work for DEC and then Microsoft around those times. Fascinating individual with some hilarious stories. I have yet to meet a more chill yet brilliant developer in my career.

[@ironhead2008]

That's some incredible luck with the silkscreen big switch on the monitor.

[@1976smb]

Thank you so much for showing your pet rabbit at the end. My pet rabbit, Honey, died on July 1st. It has been hard, but I've been dealing with it. Your rabbit looks awfully like her; I wish I could pet it and let your rabbit know it is loved, not just by you but by someone else. It brings someone some happiness and well, some sadness too.

[@bradnelson3595]

Any computer that displays a count of polygons-per-second that I can keep up with by counting on my fingers and toes is the very definition of "retro computer." Well done.

[@galeng73]

I am glad that I recently subscribed. That was just about a week ago. I do not comment often, but I did want to say that I'm a huge DEC fan. They sponsored a whole lot of my research while I was in grad school. Without DEC, I'd not be where I am today.

[@captainchaos3667]

Always gratified to see at the end that your projects are properly supervised.

[@f15sim]

It's nice to know that if I'm completely unable to find a VR201, I can bodge a cable together to use a regular monochrome screen. Here's a Nerd's Guide to D-Sub Connector Names: DA-15, DB-25, DC-37, DD-50, DE-9. 2nd letter is the shell size and the number is the max capacity of that shell size. Yes, I know you see them all the time as "DB9", but just like that kid jumping off the bridge, you don't have to be wrong too. 🤣🤣🤣 I love your work, keep it up! :)

[@tihzho]

Memories! I had an IBM XT running AutoCAD R9 and had a LISP routine for drawing squares which took forever to do! lol I was thrilled when AutoCAD Release 14 for Windows 95 came out!

[@computer_toucher]

I love how enthused you get when stuff works, it's contagious

[@ocsrc]

This reminds me of the first law enforcement graphic system. The way it draws I remember when they were showing it and I think it was around 86 Really amazing how far we have come

[@horusfalcon]

With you, my friend, there is no softball. Flawless victory! 😄

[@KeritechElectronics]

As the other Dave says, "don't turn it on - take it apart!" :) Surprisingly easy to reverse-engineer. I thought it would be worse. The designers did a good job of describing the board :). The results are super cool, I love the colored graphics on this screen - now on to making an elegant cable for this setup :)

[@KurtisRader]

I recommend reading "The Soul of a New Machine" by Tracy Kidder. I read that book soon after it was published (nearly four decades ago). While indirectly relevant to the topic of this video it explores the competing tensions of engineering something new. The lessons documented in that book regarding the Data General Corporation are relevant to the DEC terminal discussed in this video.

[@BrianBoniMakes]

I worked at a DEC VAR when these came out. I installed dozens of them and never saw a color display and we were selling color measurement equipment. Now the VAX was different, they frequently had color monitors as a secondary display. The monochrome display was always the terminal. The DEC color display was a huge and heavy monster so you're lucky you don't have that. lol.

[@lawrencedoliveiro9104]

You’d think with a name like that, you could get them at half price. 241, geddit ...

[@runforitman]

that was awesome seeing the colour screen suddenly come alive! I was not expecting it to

[@bzuidgeest]

The text button likely does something like killing the color burst signal or something like that. It makes for sharper text at the obvious cost of color. I thought some apple or such monitors had that feature.

[@8BitNaptime]

The Commodore 1950 ( some sort of rebrand but I don't know what) also has that switch.

[@the_jcbone]

@@8BitNaptime I feel some kind of relation to Commodore monitors, espacially the inset front Bezel and the pots in the back… they remind me of my old 1084s

[@Mueller3D]

Color burst only exists on composite signals, not on discrete RGB. I imagine the text button kills red and blue so only green is output, thereby eliminating any color fringing.

[@bzuidgeest]

@@Mueller3D maybe you missed the part where I said "or something like that". I also entertain the possibility that the monitor can take composite input besides RGB.

[@8BitNaptime]

@@Mueller3D IIRC, at least on my 1950, it mixes all together to create an amber equivalent display. I don't know anymore, that monitor is in deep storage...

[@jsalsman]

What a great feeling to see those labels inside the diagram at 18:22!

[@TatsuZZmage]

Last time I saw a Monitor that looked that well built was a GDM-20E20, the school I went back in the day was full of em and they were heavy.

[@BollingHolt]

Very cool! Man, I love those old DEC keyboards! I really, really want a VT220 for nostaglia's sake!

[@hubbsllc]

When I first started working it was on DEC VAX and VT220 and VT240 terminals. I wrote a graphics library for VT-240 in Pascal and used that to write a virtual logic analyzer that read output of fault isolation / circuit sim software. Even had mouse support and onscreen buttons to click.

[@BenjaminMaggi]

My sunday morning got a lot better now, thanks soon much for all the hard work to keep us mortals entertained

[@JohnKiniston]

Way cool, I had a rainbow with color back in the day. I remember playing wheel of fortune and Hoyle.

[@50shadesofbeige88]

Ah yes, a "softball video". Famous last words.

[@karim2k]

That's a modern era for the channel 😂

[@Stoney3K]

The 16/64 switch allows you to select either a 16-bit RGBI colour palette for CGA/EGA, or a 3-bit intensity which was an EGA feature. It was quickly superseded by analog VGA because not a lot of monitors had the 2 additional intensity bits wired in.

[@jsheradin]

Man the new KZbin bitrates are just awful. The screen is a blocky mess. Cool to see the monitor working!

[@jimturpin]

I remember those days, having to fabricate cables and such. Biggest problem I had once i added color to my old DOS computer was finding a color image file, and a paint program to display that image which took longer than buying the color card itself. lol!

[@jondough76]

I had forgotten about Princeton Graphics. Our first family PC had one of their monitors.

[@Kae6502]

This'll be a very useful combination! Well done and safe travels.

[@paulb4uk]

Superb work getting the monitor to work .

[@gcewing]

I remember playing around with an NEC7220 when a friend of mine was building an NS32000 based computer. Quite an interesting and powerful device for the time.

[@SonicBoone56]

Congrats on getting this to work. Crazy ideas can end up becoming great ideas.

[@DK640OBrianYT]

So satisfying to watch. Congratulations.

[@AndersNielsenAA]

Good one! The part about the caps cracked me up!

[@alexanderfederowicz]

Beautiful Reverse engineering of the cables and signal breakdown ! Been so long since anyone even mentioned Tube and signal structures !!! Usually back at that time, if you took off the back cases cover there is a schematic for the unit to assist in tuning the display or wiring the unit based on defined schematics for the output and input ports... One can hope it was not removed by a collector-O-Noid and now sits in a basement molding away or landfill ;-P

[@richgarrett4082]

I had Rainbow 100. Worked for a computer store that sold them. Got all the service parts when Dec discontinued the 100 and upgraded it to a 100+ with 10MB hard drive and the Dec color monitor.

[@ferrellsl]

Love that smooth text scrolling.

[@5cyndi]

Nice work!

[@jimsimpson1006]

I'm just watching now and even if it doesn't work it should be an interesting waste of time! 15 minutes later.... It did work, great job!

[@lawrencedoliveiro9104]

8:17 That’s how you can tell it’s a colour monitor. The kind of thing that would give me a _frisson_ back in the day, in more ways than one. 😉

[@JacGoudsmit]

I don't know anything about this DEC PC, but based on my experience with the IBM PC I wasn't surprised that it didn't work "out of the box". The monochrome and color graphics adapters were designed so that you could use them at the same time and you had to flip a dip switch on the motherboard to select BIOS (and thus DOS) text output to either the monochrome or the color display. Of course the MODE command in dos would let you switch between the monitors on the fly, once it was running. Anyway great video as always! Thanks for posting.

[@mr.fishfish570]

Very enjoyable to watch

[@danmenes3143]

Princeton Graphics--that's a name that disappeared. Back in the day they were a pretty visible high-end monitor maker, if I remember my old Byte magazine ads rightly. Today, a search turns up almost nothing. According to Wikipedia, Princeton's corporate parent still exists, but it has morphed into a credit card processing company called Corecard.

[@McTroyd]

Cool that you didn't have to actively break-out the sync signals. Maybe use schottky diodes or a resistor mixer in the final cable to merge that monochrome signal?

[@youtubasoarus]

Awesome stuff! Trying to figure out the pinouts on stuff like this is fun but nerve racking. Don't want to release the magic smoke! lol.

[@lawrencedoliveiro9104]

6:02 I think the name “Ultrasync” relates to the era, when multiscanning monitors were still a new thing. They were pioneered by NEC with its “Multisync”, but other vendors soon got into the act.

[@falksweden]

David: "I need a softball that I can knock of easy" - Reengineers a display that is unknown on the internet and connects it to the wierdest of PC:s 😂

[@BigJohn4516]

I had that same model monitor on a workstation in 1989. It was used for pcb design. I was never impressed with it, but the cable was hacked up too.

[@EsotericArctos]

I can't remember the pinouts for the Princeton, but I think it was available in 12" and 14" versions, had a maximum resolution of 600 x 800. Apaprently quite a good monitor for the time. I'll watch the rest of the video now and see how it all goes. Looking forward to seeing this :)

[@krethjr]

My first "big" monitor was a Princeton Graphics 19" color monitor. It was about 1986 or so. It weighed in at 90lbs - ouch.

[@JamesPotts]

Dang, I briefly had a Rainbow. Gave it away. Really wish I still had it.

[@jurjenbos228]

Making custom cables to connect a computer to a screen, and zillions of option switches. I almost forgot how hard it was in those days.

[@goofyrulez7914]

You find such interesting devices.

[@pianoman4Jesus]

Oh my.... @2:52 I was not aware that Matrox made graphics boards for PDP/11's! They used to be my favorite brand of graphics boards around Y2K time frame... their Millennium boards through their G550 boards. Then they stopped building boards, so I switched over to Nvidia boards.

[@dr.zarkhov9753]

Pretty 'schmick' as Dave would say. Well done!

[@philippetorgue3783]

j'adore regarder le défilement des caractères sur ces vieux écrans !

[@5cyndi]

5:37 that diagram looks like it will look nice in color; very sharp

[@neils132]

great video. curious if the Text button on the monitor would switch the monochrome mode.

[@koenlefever]

NCR had some similar machines with 8088 and Z80 CPU's, such as the Decision Mate V and NCR PC4 with the CPU's and disk drives integrated in the monitor. I know that there was yet another NCR 8088/Z80 model on the European market (my nephew owned one of those) which looked more like the DEC Rainbow with a separate monitor, but I cannot find it on the web.

[@MotownBatman]

Who Doesn't Like Softball.... Oooohhhhh Pretty Colors...

[@thekornreeper]

Pretty cool

[@JohnnyWednesday]

SGI machines use Sync on Green - the monitors are increasingly rare.

[@e7yu]

Nice, more videos.🤠

[@UpLateGeek]

Get a load of the length of the analog [sic] /TTL switch! That thing's a monster! Sync on green is evil. I had a monitor back in the day that just had RGB input BNCs, and it took me a while to work out that it used sync on green. The circuit to convert RGBHV to sync on green is pretty simple, and I did hack together an adapter that worked, but I eventually found a place that sold a proper adapter cable that was a much neater solution.

[@petermikus2363]

20:21 that Ti expansion looks to be on edge.

[@DerHeimatlose1]

Such a cute bunny

[@andydelle4509]

I am proud I was one of those in the mid 1980s who had to learn how to program an NEC7220 or Motorola MC6845 chip at the register level! Custom Character font? Go build it in a bit mask and burn a PROM!

[@andygozzo72]

yep, you dont HAVE to always replace all old electrolytics, they may well still be ok 😉

[@batlin]

That smooth scrolling is so good... there was a program for the Atari ST called the Revenge Document Displayer that allowed fast smooth scrolling and was similarly pleasing. I wonder if any modern Unix terminal emulator does it.

[@Lion_McLionhead]

A lot nicer than the lion kingdom's regis demo because it does line fills.

[@halfsourlizard9319]

Love your idea of a low-effort vid.

[@MrStevetmq]

The DEC Rainbow is a really interesting, two different CPU's in the same computer.

[@frankowalker4662]

Nice monitor.

[@steenhansen8]

“This whole video may be a total waste of time”… yaaayyyyy !!!

[@edmonk4912]

Back in the day, late 80's, I remember throwing dozens of these out into the dumpster as they were replaced by IBM Model 30', 70's and DEC FX. We were told to make sure if someone goes dumpster diving that they will not come back with a working system. Its kinda sad now, but back then people were really looking forward to getting their hands on a much faster IBM, and were really glad to see the rainbows go away. Plus we introduced 10Base2 networking, and suddenly people could file share among other things. The PDP 11's were replaced with the VAX 11780's (3 of them) at the time as well.

[@lawrencedoliveiro9104]

Why is there this need, if something is useless to you, to go out of your way it will not be useful to anyone else? My mother had the term “dog in the manger” for that ...

[@lawrencedoliveiro9104]

@tradde11 So if you want to make money off the items, sell them.

[@lawrencedoliveiro9104]

@tradde11 DEC couldn’t care less. This wasn’t DEC doing it.

[@lawrencedoliveiro9104]

@tradde11 Maybe you are misunderstanding the OP; their employer was using, not selling, the gear.

[@SeekingTheLoveThatGodMeans7648]

As best I could see, it does look like it is still syncing on green, as green is doubling for monochrome. So you hit good fortune there.

[@andydelle4509]

If you ever need a ultra simple sync separator look at the National LM1881 chip. Broadcast quality circuit in an 8pin DIP with minimal external RC components.

[@JCBudro16]

Wow I can't believe Bunny-san would power up that poor defenseless monitor without first giving at least three hail-mary's and making a small sacrifice to Baal.

[@brianh.4185]

Genius.

[@andljoy]

100% agree be carful around CRTs kids , i have been spiked by a little 9 inch monochrome one that was bad enough. When servicing some sony BVMs i was very carful i can imagine if you get spiked by a colour tube of that size i dont think you will live to tell about it .

[@joe--cool]

Don't touch the high voltage zappy bits is good advice. Or don't open what you don't understand when there is a wall of warning labels. I am glad you are still well and can tell the tale.

[@alanparker3130]

My first PC! The UK Atomic Energy Authority was VERY suspicious of PCs. Their workhorses were all things DEC, mostly VAX, but they were useless for interfacing to experiments, so after much huffing and puffing, I was allowed a PC, IF it was made by DEC.

[@CornGuo]

As a Taiwanese, it's fascinating to see that they're manufactured in Taiwan :p

[@johnfarias7230]

Full color graphics I laughed my ass off Although I really really wish I had one

[@badscrew4023]

I wish I was smart enough to do things like that :)))

[@boardernut]

I was wondering if that pdp11 can also display color if it had some framebuffer adapter, if such thing exists and what software for the pdp can take advantage of it

[@GoingtoHecq]

More like rgb in usagi electric. I love the bunny Anyways you DOS and other vintage computer people never seem to really stick to using things as they were originally intended to be used. You mix and match the parts and write programs to make it work.

[@guilherme5094]

👍!

[@chongo333]

We need you to do a softball IVIS video =)

[@68hoffman]

kool

[@david0fc]

What was the text button in the monitor for? Have you figure that out? Maybe for non color signals?

[@GregStrike]

Ahhh, the static on the monitor. I forgot all about that!