Booting MS-DOS, CP/M and RSTS/E* on a DEC Rainbow!

I have a problem. I’m all out of space in the room for CRTs, but I don’t have a single machine in the room that can boot DOS or CP/M. Almost every CRT in the room is dedicated to either a unique system or lives life as a data terminal. So, it’s time to start consolidating. And in this, DEC has got my back. The Rainbow 100 is an epic little triple-use machine that can boot MS-DOS and CP/M as well as work as a VT-100 terminal. This thing is really, really cool!
*: I fully realize that in the title I say, “Booting MS-DOS, CP/M and RSTS/E,” but the Rainbow 100 is incapable of booting RSTS. In this case RSTS is being booted by the PDP-11/83 and the Rainbow is being used as a VT-100 terminal. But that was all a bit too long to write in the title. However, if you're still upset about the title, write "I read the description, and I'm still pissed!" and I'll get a good chuckle and actually read your comment.
If you want to support the channel please hop over to Patreon:
/ usagielectric
Also, we now have some epic shirts for sale!
my-store-11554688.creator-spr...
Come join us on Discord and Twitter!
Discord: / discord
Twitter: / usagielectric
Intro Music adapted from:
Artist: The Runaway Five
Title: The Shinra Shuffle
ocremix.org/remix/OCR01847
Thanks for watching!
Chapters
0:00 I have a problem
2:13 And the only cure is more cowbell
4:39 Disassembly
6:00 A look at the boards
8:34 A look at the PSU
9:16 Cleaning and reassembly
11:44 First boot
13:20 Copying IMDs to floppies using the Greaseweazle
17:17 Testing out the DIAG program
18:47 Booting DOS and CP/M
21:24 Booting RSTS on the 11/83 and using the Rainbow as a terminal
22:56 This thing is cool as
23:51 Bunny!

[@UsagiElectric]

NOTE: I believe there is no such thing as "Quad Density" disks. I just used regular DSDD disks here and it works fine. However, the term "Quad Density" in reference to how the data is stored may have been used a bit more commonly. What I think is going on here is that DEC wanted to emphasize that they were storing 80 tracks / 400 kb on just one side, which is pretty wild. So, in that sense, the term does fit. Again though, "Double Density" disks work just fine here.

[@Figulus]

Hello, David, I hope you are well. I have a few questions about the drives that I wanted to ask... Since all 80 tracks are written on just the one side of the floppy, would it be correct to infer that a further 80 tracks are free to be written on the blank side -- hence the name 'Quad Density,' because it's "double Double Density"? Additionally, the Rainbow 100 menu lists drives A, B, C, D, & W, with A and B being the two slots in the RX50 disk drive. Thus, I'm thinking that drives C and D would be the designations for each of the slots in a second RX50 module should it be installed in the empty bay, whereas W would refer to a Winchester [hard]drive if it, instead, were accommodated therein... Is this reasoning correct?

[@orsonzedd]

Gonna wait on Octuple Density Disks tbh

[@the123king]

Yes, quad density isn't really a thing. I think it's some reformulation (finer grain) of the magnetic material used in DD floppies, but otherwise not really a difference from DD media. You can find DSQD floppies for sale occasionally, so i do suspect there's some kind of difference in formulation/manufacturing, but not sufficient enough to make a difference in reality

[@inerlogic]

Oh my God I'm having nightmare flashbacks the DEC rainbow is what my high school had typing classes on in the 90s

[@paulstubbs7678]

I have a pair of 80 track Mitsubishi drives fitted to a TRS-80 to give me more storage, the disks I bought back then were Xidex "Double density 80 track", I think the term 'quad density' came when IBM started doing the 1.2/1.6 meg disks on their PC-AT line, These disks have different magnetic properties and generally don't work in these 'regular' 40/80 track drives. I've used 40 track rated disks in these drives with no real issues, the 80 drives are just a bit more fussy than the 40 track drives - as in more likely to find dead sectors on a 'not so good' disk.

[@exidy-yt]

Holy hell, DEC's hardware designers had their brains in high gear putting together that rig! What a sensible, logical and HELPFUL design that case has for dis-assembly and re-assembly!

[@SeanBZA]

Meant for easy field repair and easy assembly both in factory and field.

[@lemagreengreen]

You spent the money in those days and you got something that at least felt worth it, even at this 'low' end desktop stuff. Reminds me a little of SGI later on, they'd take many thousands of dollars from you but the hardware was heavy, extremely well designed and at least felt somewhat worth it.

[@cda32]

And the key word *expensive*

[@rabidbigdog]

It really pissed-me-off that Jobs arrived claiming all the tool-less service. He didn't even believe you should be allowed inside your own computer for a start!

[@cda32]

@@rabidbigdog That's not accurate. Jobs had nothing to do with that it happened under Tim Cook and Scully. Apple desktop systems under Jobs had amazing serviceability, and even most macbooks compared to PCs at the time. Jobs and Woz made sure their machines were just as beautiful on the inside as they were on the outside.

[@haraldtscherne7487]

Thank you for bringing back some 40 year old memories. Back in 1982/83 I was amongst the first DEC Field Service Engineers in Austria to repair that fantastic machine, after seeing your video I'm confident that I could still disassemble and reassemble it blind-folded. I remember the first generations of hard disks had a high failure rate, back then I've seen several customers panicking because they didn't bother to back up their data before the drive failed. Did you know that several Rainbows can be seen in the police office in the movie "Beverly Hills Cop" (1) ? Keep on the good work and your enthusiasm, I enjoy watching your videos very much!

[@yorkan213swd6]

Servus weisst Du noch wo man in Ö eine bekommen kann ? LG

[@thek3743]

Sehr leiwand!

[@cyndicorinne]

Wow I love the smooth scrolling of the Rainbow terminal.

[@SeanBZA]

That power supply does have 4 RIFA capacitors in it, in that sealed can by the power inlet, in the sealed mains filter unit. They however are potted in bitumen, and then soldered in, so are very difficult to get to to replace. However they will likely blow up and not release smoke as they go bang, as the case will probably contain it, though you will pop a breaker, as the filter is both before the switch and the mains fuse. External 5A fuse in the power lead is a good recommendation for it.

[@jeroen1158]

The Rainbow 100 was my first first computer back in 1984. my dad brought it home from work one day. He was working for DEC at the time, and employees were allowed to take computers for home use. It was great, I got the catalog with the computer so I could 'order' any software or hardware upgrades available. In the end I had around 20 of those big boxes with software next to the computer. I installed the Winchester drive as well. 10 MB, a huge capacity for the time. I did my best to fill it up, but never did. Unfortunately the machine went back to the company, and nothing else of it is left. There was also an external modem that I used to dial into remote computers like at Stanford, MIT, NASA, etc. It was just magical to see the main menu of the server system load character by character on my monitor in the basement. Quite an experience for a 16 year old. Thanks so much for this video. It brought back a lot of memories. Also the disassembly, I did that so many times, analyzing the circuit board, trying to imagine how the computer worked. I could go on and on in this post :-)

[@achimboers]

Hi, similar story .. also my first computer my dad brought home from work !!

[@jeroen1158]

@@achimboers it's too bad I didn't get to keep it. Sad to think it was just scrapped when we returned it.

[@davistroy]

I lusted after a Rainbow … DEC was the pinnacle of real computer hardware. Thank you for finding and restoring these old machines

[@Clavichordist]

I noticed the NEC 720C graphics chip on the motherboard. This chip supports monochrome vector graphics and was quite expensive at the time. The Toshiba TMM2016s are 16K-bit static RAM (Thank you Peter_S_ for the correction). I remember seeing both of those on Visual terminal motherboards. Their V-550 graphics terminal used the NEC 720C, and the TMM2016s were used on many models along with the usual DRAM. In the late 80s to the early 90s, I used DEC Rainbows extensively for various tasks including editing and printing out the labels for the backup tapes. These were great systems in their day and DEC always made top quality equipment. If only current manufacturers would take this page out of history and build new equipment to the same standards today as we saw back then. It's sad that they were carved up by investors and set out on the market for sale, and more unfortunately that HP purchased them along with the Compaq mess to create what I referred to as Humpback corp. Having dealt with DEC service and support then dealing with the HP/Compaq mess afterwards, the difference in service was like night and day and was a foreshadow of what we have today.

[@Peter_S_]

Note the TMM2016 is a 16K BIT chip, or 2K bytes. My Timex/Sinclair ZX81 used the same chip, also from Toshiba.

[@Clavichordist]

@@Peter_S_ Thanks for the clarification. It's been close to 40 years since I came close to those devices. I was going through my brain cells trying to remember the details.

[@frankowalker4662]

That is some design thought that went into the DEC. Bloody impressive. Fantastic system.

[@UsagiElectric]

DEC was killing it with the design of this thing, it's super cool!

[@frankowalker4662]

@@UsagiElectric I was also very impressed with the Diag software.

[@lawrencedoliveiro9104]

A company run by engineers, selling to engineers.

[@frankowalker4662]

@@lawrencedoliveiro9104 You can also tell they took pride in their work. Unlike today with all this cheap mass-produced rubbish that breaks after a year.

[@highpath4776]

@@UsagiElectric Still managed to kill my collegues MS-DOS stored files using the MOVE command in CP/M arse over face in a file cleanup day.

[@HoJoGoGo]

One of the things you can do with the Rainbow with VR-201 and the graphics card is to run Autocad, it will support monochrome graphics.

[@wesleymays1931]

Computer is called the Rainbow Has monochrome graphics

[@HoJoGoGo]

The Rainbow has color graphics with that add in card, just takes a different cable and RGB monitor for color.

[@mrzap0]

I remember buying my first mouse to use on that 🙂plus some of the old demo files. There was the old space shuttle one that seems to be shown everywhere, plus an office layout one, and a solar system to scale one. The office one could be shown in full 3D (although it _really_ look a long time to draw on our system) and the solar system one you could zoom in on each of the planets, etc. On the moon you could go in as far as the lunar lander which had a plaque with writing on it.

[@DmitryEljuseev]

Man, your channel is absolutely amazing. Especially compare to other reviewers who have 3-5x more subscribers but mostly reviewing Commodore or Petskii robots for years. You have now a collection of really rare machines, which most of us will not be able to see without your channel, respect and keep going :)

[@Starchface]

It is true that David has amassed an eclectic collection of equipment that most of us will never see in person, as well as designing and building his own tube-based computer, the UE-0001 (ish). His award at VCF was well deserved. That said, I also enjoy the more conventional microcomputers of the '80s and '90s and the channels that cover them. Through them I relive the glory days, the Golden Age of computing as I think of it. There is room for everyone.

[@cdl0]

Another great video: Such is Usagi Electric's huge enthusiasm for the DEC Rainbow, that had he been a salesman for it back in its day, then it would have been a colossal success in the market.

[@highpath4776]

The Price was the problem. More expensive than IBM clones.

[@cdl0]

@@highpath4776 Penny price, penny quality. We can all see from the video the incredible quality of the DEC Rainbow. Moreover, the fact it still works after forty years is a testament to its excellent construction.

[@colinstu]

3:00 THANK YOU for showing how this drive worked! I've seen pics of them for over 20yrs and could never imagine how that mechanism worked.

[@UsagiElectric]

It's such a confusing looking little drive, but very neat to use. I find it hilarious that the bottom disk has to be inserted upside down! That tripped me up for a bit the first time, but it makes sense if you think of it as two half-height single sided drive jammed into a single full-height housing with the bottom drive flipped upside down so they can share the same motor.

[@paulcollis2872]

The effort that Dec put into designing these drives is impressive. They are quite heavy and employ alot of metal in the construction. The RX50 was used in other DEC computers too

[@scottyb069]

I'll never forget being a work experience kid with DEC back in 1983 and being let loose on the new DEC Rainbow. It's a machine I always wanted after that but had to make do with a Commodore Vic20. I'll also never forget the technician they put me with, aparently a cross dresser who drove the work van like a race car, flat shifting and double shuffle, never used the clutch, funny guy.

[@hessex1899]

DEC hardware build quality is next level. In my old house/hackerspace back int he 90's we threw a MicroVax II out of a 3rd story window into our back yard. We pulled it out of the dent that it left in the yard, dusted it off, and it booted right up.

[@alexcrouse]

DEC machines are clearly meant to be serviced in an office by a tech from the factory as quickly - and cleanly - as possible. Never worry about your tech dropping screws again!

[@ShulerBurton]

A Friend had a rainbow back in college… ran dos and wordstar and a printer. Was a really nice machine in 1986. My c128 ran cp/m also but finding disks was difficult ! C64/c128 had a big software library so cp/m 2.2 seemed interesting but didn’t pursue it much.

[@BoredInNW6]

For a while, DEC (at least here in the UK) were giving Rainbows away, possibly in an attempt to jumpstart lacklustre sales. My employer at the time got a couple that way, and they made perfectly competent (if bulky) terminals for our VAXen.

[@retrobreutje]

CP/M-86/80 was a special version of CP/M for the Rainbow that booted CP/M-86 on the 8088 CPU, but would execute 8-bit CP/M programs on the Z80. You could run both 16 bit 8086 and 8 bit (8080/Z80) executables. Mine was left at the garbage dump (by me) way back. Most MS-DOS programs did not run correctly as most programs only had CGA or VGA support.

[@kevincozens6837]

At 6:49 the 2016 chips are 2k x 8-bit static RAM. I just love the construction of that DEC system. Someone did a really good job making it easily serviceable.

[@nigeljames6017]

The fun and excitement of running old software on old computers is thrilling. May this never die !

[@adilsongoliveira]

What a beautifully engineered machine. No screws, no loose cables, everything neat and organized.

[@mekafinchi]

I have a rainbow myself, its a really cool machine. The uniqueness of its hardware is both its greatest blessing for its ability and greatest curse for its incompatibility.

[@Taisen_Des]

Oh, man. That room is a dream place that every systems technician would have wanted for his home ... in the 70's ☺ ...and in other times too. 👍

[@BollingHolt]

Oh so cool! I didn't know such a beast existed! I have a soft spot in my heart for DEC equipment. After fifth grade (Summer 1992), my computer teacher arranged for me to audit a Fortran 77 college class at Auburn University Montgomery. All the work was done in a lab full of VT-220s that connected to a VAX/VMS system which was vastly different than the CoCo2 and Amstrad PC1512 I had at home!

[@garyarnold8288]

I moved from Data 100 to Northern Telecom and then to EDS. Retired out of EDS after 30 years. All of this is so familiar. Worked on so many of these pieces of hardware.

[@UpLateGeek]

Very interesting machine. It's like they were hedging their bets on everything from Z80 vs x86 to MS-DOS vs CP/M, and threw in the VT-100 terminal option because of course DEC would include a terminal. It's just a shame about the limited MS-DOS compatibility, it could've really been the Swiss army knife of computers if they just made it a little more IBM clone-like, and I'm sure that would've made it a lot more successful.

[@andymcgarty3099]

We used to run Concurrent CP/M, an O/S ahead of its time but without the backing/manipulation of Microsoft it never really took off. That A/B switch brought back lots of memories. So you think you'll get something running OS9 or OS9000, an great Unix alternative when you needed realtime for the collection of serial data etc. Great video as always.

[@highpath4776]

Would the Rainbow run UNIX (we used informix on DEC VAX units

[@petergathercole4565]

@@highpath4776 There was a UNIX port that would run on a Rainbow 100. Venix version 2 from VentureCom was an officially licensed UNIX Edition 7 port that ran on a Rainbow 100. There is a Wikipedia page on it at en.wikipedia.org/wiki/Venix. Having not used it, I would guess that it is a function-limited version, as the Rainbow 100 had an 8086 processor without memory management, so although it was supposidly a multi-user system, there was probably no process memory space segregation, meaning it would be easy to corrupt the processes of another user. As version 2 of Venix was also intended for an IBM XT, I expect that it would require a hard-disk on a DEC Rainbow 100.

[@InssiAjaton]

I remember "lusting" for the DEC Rainbow, while also pondering if the AT&T version of a PC might be any good. However, what I bought was an HP-87. It natively booted into HP version of BASIC, with 10^-500 to 10^+500 numeric range (approximately). It also had a built in IEEE-488 bus for instrument control. And it had 4 expansion slots for additional memory, or various ROM applications. One module provided RS232 serial communication and a monitor functionality. But then, I got a Z-80 co-processor module and besides its CP/M, I had some version of FORTH for it. All that, when the company got a TRS-80 Model 1 for inventory control and then a Sperry PC with a buggy DOS 1.15. Next company PC was an XT with a 20 MB hard disk for the accounting. It came with DOS 2.11 (which the Sperry had also been upgraded to). From there on, it was all IBM, including me also having to go along, for compatibility reasons.

[@AKATenn]

this is my favorite youtube channel, every time I watch one of these videos i already wish it was sunday again lol... I would like to start collecting old computers and repairing them too, but every time i nearly bite the bullet and buy one, i think... "what actual use do i have for a computer that has less cpu power and memory than my keyboard?"... yeah i can repair it, get it working again, but then it sits on a shelf, then when i get rid of it it'll either get scrapped, or sit on someone elses shelf till it needs another restore... maybe that's the point, so it'll still be around for whoever's next... but then someone alot more professional than I am would probly do a better job than I can... for now, i'm just maintaining my 90's console collection...

[@TheThomasites]

You've aligned those zip ties perfectly to give the next person in there a good slice.

[@UsagiElectric]

I'll be the next one in the system for sure, so future me is probably going to fully agree with you, haha.

[@Sven_Dongle]

@@UsagiElectric Get yourself a 'god hand'.

[@F4LDT-Alain]

The Rainbow was a great machine. Sharp display, excellent keyboard. I've used one as my main terminal to administer a big VAX 8700 many years ago. With Kermit under MS-DOS, it was an ideal "smart" terminal. I was happy hearing the quite recognizable sound of the RX-50 disk drives again . Thanks for this great moment of nostalgia,

[@lawrencedoliveiro9104]

22:02 I only used versions of RSTS/E from around V6C to V7. What you have there is a later version where DEC ported a version of its DCL command interpreter from VAX/VMS onto its PDP-11 systems. Making it kind of a standard CLI across its different OSes (subject I guess to particular OS limitations).

[@HoJoGoGo]

I used Teledisk to write disks for my Rainbow back in the 90s, using a 1.2MB floppy drive on a 286/12 PC. You do have to have a 1.2MB drive on a DOS PC to use the original Teledisk software.

[@kellingc]

Ah, yes. I used to have 2 rainbows, One had a graphics card, and 2 RX50s. I could boot from any of the four drives or go into VT102 mode and use it as a terminal. I learned about vector graphic on it. The other one that a 10 Meg HDD which I played around with Turbo Pascal ver 3.3 in MSDOS or CP/M.

[@UsagiElectric]

I'm gonna keep a close eye out for a Winchester controller, I would love to stash a 10MB HDD into this one! It's a really neat system, and once you get past the weird quirks, it's a ton of fun to use!

[@kellingc]

@@UsagiElectric Be aware, I think there isn't a parrallel portt. Look for a DECWriter of somesort because they are all serial printers. It's all 8 bit ASCII, so if you have a printer that does serial communications, it should work. Same thing with the PDP's you have.

[@mikehebdentrains]

Apologies if others have already mentioned this, but I recall that Digital Research produced their own DR-DOS version alongside the Microsoft offering. In the UK, ICL used CP/M on their modular DRS range in the mid 80's. We had lots of fun in CP/M changing to 'user 1', 'user 2' etc, although never found a reason to use that feature for any real purpose. nice bit of nostalgia, thanks!

[@KennethSorling]

As soon as the cover came off, I was amazed at the clean design and the plethora of space inside. As you kept disassembling it, I was even more amazed. Why didn't every computer manufacturer take a clue from DEC on how to put a machine together?

[@TLang-el6sk]

Back in my time at university I attended a microprocessor internship. Besides other hardware we had CP/M systems there which - as I learned later - were developed and built by my future employer. I also possessed a C128 which I used to to my homework for this internship. The C128D CP/M had some nice features, e. g. it supported various disk formats. The format table could be extended which I did to support the disk format used by the systems at university. So I was able to directly work with these disks. As long as no special hardware (like GPIOs, ADCs/DACs) were accessed I could write, compile and try out my software on my C128D while doing the final steps on the university machines...

[@lhpl]

Your title had me fooled a sec - I thought you might have found some kind of LSI-11 extension card for the lovely Rainbow. I learnt programming on the Rainbow, using the Z80 predecessor to Turbo Pascal, on CP/M-80. I remember there was an amazing Pac-man game, written in Mark Williams C (no source though, but it said so), and some kind of quest or adventure. But to me, having all the advanced features of a VT220 terminal was the biggest joy. Some years later, at the university, learnt MACRO-11 assembler on its "bigger brother", the Pro350. I have such a Pro350, but I'd love having a Rainbow100 also. Computers are just not built like that anymore. A work of art, pure beauty.

[@tomking6006]

I remember that motherboard! When I was small someone gave me one of these boxes and I'm afraid that not knowing any better I took it to bits - but I remember that very distinct motheboard design! The 12V fan was an absolute beast and I used it as a desk fan for years.

[@LenPopp]

You had me at RSTS/E.

[@johnjon1823]

We ran CP/M for a while and went to MP/M to gain some more terminals on an Altos machine back in 1982. That Altos never failed us, and MP/M allowed us about 3 usable terminals per machine due to memory and CPU speeds. We could enter data on 3 terminals at once. It was awesome. The we added a racal vadic modem and could log into a remote system out of state to send data via kermit. That machine allowed our business to expand like never before. We eventually migrated to dos due to some software needs and ran under dos for more years. In the end we were over tp XP which was a nice OS. We paid something like 13K in 82 for the Altos, one monitor, a used dec writer for a printer, and software packages. That's about 41K today. I think it had like 256K total RAM, and it had a 20 meg hard drive and 8 inch floppy drive. That modem cost a fortune at least 1200 in 2023 dollars. It was a specialized modem to connect to, I think, a DEC system. We had a remote account, logged on as a terminal and then executed Kermit at both ends. For the time this was amazing. As I recall, that part occurred in 85. Other modems were cheaper, I want to say Hayes modems, 1200 baud was a big deal, then they had some kind of 56K thing.

[@unclefreddy2009]

Wow memories….. I owned one of these back when they came out. We owned a small retail store and I used this to run dbase perhaps even on cpm. I wrote some rental software back in the day to run our rental business. It was bad timing because if I had waited a year I would have just bought a pc, but this was just before the revolution. One thing I remember is how difficult it was as an individual to buy this machine. Dec was set up only really to sell to corporate and getting them to even talk to me was difficult.

[@eric_d]

I remember getting a DEC Rainbow out of the dumpster at TCF (Trenton Computer Festival) when I was a kid. One of the vendors had thrown out several of them, and I grabbed one for myself, and almost had to fight some guy who tried stealing it from me. I honestly don't know what the big deal was about them, and why they ended up in the dumpster if everyone was arguing about who was going to get them. I never actually booted it, as I had no keyboard or monitor that would work with it. I just remember the 8 LED lights on the back that would flash a pattern when the machine was powered on. My mother tried throwing it away on me several times, and I ended up having to hide it in a locked cabinet that she didn't have a key to. The computer is long gone now, and I've still never seen one booted up, so I'm excited to watch this video now.

[@exboisv]

Ford Dealerships used them a lot. I used to use the Rainbow 100 when I was a teenager at a Ford Dealership to do warranties, order cars, etc.

[@markmuir7338]

That's a beautiful computer! Given your ever growing collection of computers needing a terminal, I think a more scalable and seamless solution would be to have a Raspberry Pi hidden away somewhere behind a real serial terminal, acting as a switch that refreshes the entire display when you switch between computers - like tabs in a modern OS. The Pi would have a USB hub and one USB to RS232 adapter for each computer you have, plus one for the terminal. Some simple software would record the screen buffer for each computer separately and forward the appropriate one to the terminal. The software could listen for a special character sequence to switch displays, and would redraw the entire display when switching. I'm sure someone in your fan base will be willing to write that software.

[@hellraizer322]

I really enjoyed your video about the DEC Rainbow! It was fascinating to see how these operating systems worked. I'm a big fan of old computers, so I really appreciate your work preserving these machines and sharing them with the world. Thanks for the great video!

[@DrJaneLuciferian]

I've got a vt-320 terminal here at home, and it has both a 232 and 423 interface on the back, and rs-423 is available on the various dec mid-size office 11 machines, it's quite common.

[@oldnotobsolete.2925]

The Rainbow is one of my two "dream machines" that I'd love to own. Unfortunately, both it and the Northstar Horizon rarely appear here in the UK. Back when I worked for DEC in the 90s, there were quite a few of these in various parts of the building but I never got to use one as I was based in the networking team dealing with VAX systems.

[@oldnotobsolete.2925]

@tradde11 Well, "horrible" is relative when the alternative is no availability whatsoever! I've been keeping an eye on eBay US as well on the off-chance that one will come up with international shipping but nothing at all, international or not. I would be curious as to how much it would cost, if you ever got the chance.

[@Peter_S_]

Surprise; the diagnostic card for your Centurion has a place to plug in a Z80 and it can likely be used as a Z80 CPU card to run a minimally changed variant of CP/M. One of the DIP switches (switch 8, which is not not stuffed as your board only has a 4 position switch there) selects bus mastering mode for the diagnostic card and lets the Z80 run, otherwise it operates strictly as a peripheral and you can leave off about 20 chips. To support the Z80, you would just need to add a few chips and write a bootloader to put in EPROM on the card. The only question is if the backplane is behind addressed latches or if it carries a buffered copy of the actual buses. The missing chips at B2 and J3 are a mystery but it was pretty easy to ID most of the rest of them with the only real exception being the quad latch at A8 which may be an old National chip.

[@JawzXlives]

I've used Rainbows in a computer lab before and took advantage of terminal, DOS/win2 and CP/m, but I never knew the hardware was so lovely and modular!

[@lindoran]

Fun fact rainbow version of dos is the basis for the kernel for the v20-mbc2 which is a x86 SBC running in minimum mode and might be the only system out there (that I know of ) that can run dos from minimum mode

[@stigmarestroom]

In 1984 I used a Rainbow 100 for calculation of radio links for mobile telephone in Spain. With two monitors attached, one monochrome for text an a color one for graphics, a dot matrix printer and a HP 7220A flatbed plotter.

[@workaholica]

I heard about the Avatar TC100 from 1983, which could be used as a terminal gateway, but also to run CP/M or MS DOS locally. Like the rainbow, it used both a Z80 and an 8088 processor. For a short while, there seems to have been a market for this class of machines.

[@ClausB252]

In early 1985 I went to a job fair in NYC and talked to the DEC rep. She offered me a job on the spot programming apps on the Rainbow. They must have been desperate! I declined it though. Thanks for showing me what might have been.

[@RobMoerland]

Back in the day we had a DEC Rainbow because we sold a lot of DEC stuff. It ran the DEC version of MS-DOS. But it lacked one command: FORMAT. So you had to buy formatted floppy disks from DEC. And those were really expenditure.

[@paulstubbs7678]

A very nice machine, love the smooth scrolling, Surprised you didn't pop the ROM;s and make images.

[@ChristopherHailey]

That was everyone's reaction to DECs smooth scrolling and then the novelty wore off and then they would turn it off. The DEC displays looked great and that was a nice thing about the rainbow, the display quality was miles ahead of the IBM

[@44Bigs]

I was once given one of these as a teen in the late 90s. The smooth scrolling was cool but besides that I had no idea what I had so I passed it on. Glad to finally see what it can do!

[@pinealservo]

The Rainbow supports an interesting graphics mode (both as a terminal and running an OS) called ReGIS (Remote Graphics Instruction Set) that can draw simple graphics (lines, polygons, text) via a set of control codes. Would be fun to see some software using it!

[@tonycoombs17]

Another great episode. Each week I can't wait for the next video. Thank you so much for your dedication and efforts to bring us interesting content every week! Keep up the great work!

[@12Q46HPRN]

Very awesome! Love the retro-tech coming back to life x3!

[@BalancedSpirit79]

Thank you for being you. This channel is such a throwback and reminds me of the wonder I felt when I got my first PC. I never had anything as old as what you showcase, but I did have a Tandy 1000 HX when I was 8. Only 256k of RAM, one 3.5" floppy drive which only took 720k diskettes, but it was still awesome.

[@munnsie100]

The design and build quality of these machines is seriously impressive and so evident of the engineering effort that went into them. I would love to collect some DEC equipment myself, but it is rather scarce in Australia (beside a very large museum collection, mostly comprised of examples preserved by the late Max Burnet, a long time employee of DEC Australia).

[@kensmith5694]

IIRC, the biggest problem with the Rainbow was that it cost too much. It could have been a good product line but for the waaaay high cost. As I recall, you could get newer DOS versions to run on it but a few things wouldn't work. There were some oddball machines back then. On some of them, maybe including the Rainbow, you needed to do the debug command in your autoexec.bat and poke a few things to make DOS work right with it. Basically, it was doing things that IBM machine BIOS did so that all the memory locations looked right.

[@null_carrier]

You built a beautiful compact setup for yourself. Three classics on one table. Excellent!

[@bdbensley]

used to sell these in a computer store I worked at in the 1980's. Love the DEC Rainbow! Wish I had bought one, or got one somehow.

[@n2n8sda]

This was the first home computer I bought after getting a job in the mid 80s.. it was 2-3 years old by then but had so much fun with it. If I recall it was around $1550 at the time.

[@hadet]

This was an awesome video, what incredible engineering.

[@garthhowe297]

That was from a time when PC's were designed with relatively little concern for cost. I love the old Compaq PC's, but DEC really set a very high bar for design.

[@OktoberTrey]

I grew up on RSTS/E, which we pronounced “ristus”, so I really enjoyed watching your video! I still miss DCL.

[@AlejandroRodolfoMendez]

Honestly that's a amazing computer, cool to see it working well.

[@cyndicorinne]

Wow I remember getting a diskette with CP/M with my Commodore 128D. But it was pre popularized easy Internet searching, and there was little to no documentation, so it wasn’t super useful to me.

[@retrogamer33]

That scrolling is super smooth.

[@suvetar]

I love this stuff! I used to program Vax and Alpha under VMS back in the day, using DEC's DIBOL language! I can't get over how smooth the directory listing is at 20:45!

[@amartini51]

I that’s the VT “smooth scrolling” feature - in a previous video, some folk were talking about what they liked & disliked about it. Makes me wish modern terminal emulators had this option.

[@stephenbraddy9925]

20:45 That smooth scroll in DOS! What the heck!

[@slincolne]

Either your camera is magic or that CRT is very nice and crisp. Excellent acquisition !

[@eDoc2020]

That's the magic of a monochrome CRT.

[@mattsword41]

the blue valve computer in the background looks so cool!

[@Cassandra_Johnson]

That is some disturbingly butter smooth scrolling!

[@rsbohn]

Love the smooth scrolling on the Rainbow!

[@edgeeffect]

2 of my favourite OSes from my youth... and MS DOS ;) .... doesn't the WangWriter do CP/M ?????? WOW! that was the easiest disassembly ever! Love DEC!

[@jimbass1664]

Dual boot like your granddad did it. Also that smooth scrolling gave me nostalgic tears.

[@BrianBoniMakes]

Seeing that thing boot brought back a lot of memories.

[@bzuidgeest]

You have multi port serial cards for many of your systems, including the vax. Any single one of them could be used as a sort of serial multiplexer for the other systems. That would not give you cpm or dos, but it would allow you to use all systems through a single crt. And considering you're now using an 8080 to run dos, I would think that at least one of your systems should be able to emulate cpm or dos. If that kind of software was ever written for them.

[@GigAHerZ64]

I love the smooth scrolling! :O

[@Raul_007]

Amazing machine. CP/M was my first operating system that I worked with. Many memories ! Greetings !!

[@femboichik]

that smooth scrolling is something 🤤

[@paulwratt]

BYTE Magazine has a nice review of the DEC Rainbow - its really interesting looking through their advertising sections in later issues at the price for the DEC Rainbow

[@poofygoof]

We used a rainbow in college as a dumb terminal to a cisco STS-10 terminal server. I always heard rainbows were problematic compatibility-wise under DOS, and it couldn't format its own disks. (Maybe a VAX could write them?) I always loved the mechanical design of DEC equipment though, even though it always felt very bespoke.

[@FilipiVianna]

Wow... Digital Research OS running on Digital Equipment Corporation hardware... How nice was that. Thanks for sharing.

[@abx42]

These episodes just keep getting better and better. When you started this channel, did you ever expect this to be where you would end up??

[@christopherpetersen342]

I definitely miss my Rainbow. It was stolen back in the 80s. I can't imagine the thieves trying to sell it though. The Robin was good fun as well...

[@TiBosRetroComputers]

Damn... I love the smooth soft scrolling on that CRT... I think I'll have to go looking for a DEC Rainbow 👍

[@dmc716]

Truly epic :) enjoyed the video very much

[@donkimble]

Damn this is a well engineered thing. Don’t see enough design focused on ease of maintenance anymore. (Apple I’m looking at you.)

[@yonaguska2050]

That's an awesome setup!

[@CrippleX89]

You were spot on with the memory… 384k includes the 64k on-board memory 😉

[@mechaform]

Nice problem to have. Used a PDP11 for a volumetric ink dispensing system in the late 80s. This system was replaced with a few IBM PS2s running DOS 4.01, which was a hell of a change from a hardware perspective. The DEC catalogue had ridiculous prices for components; a floppy drive was over $700. But it was solid equipment. Would love to have a VT320. RIP Gary Kildall

[@phildem414]

This looks like a cadidate to a retrobright! And no caps to change 🤯

[@MajorTom719]

Love it! Modern companies need to learn from DEC.

[@markpeter9919]

I like the very smooth scrolling when you dir on the Rainbow 100 :-)