Building the most controversial Z80 Computer ever
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- čas přidán 29. 06. 2024
- In this video, I will be building and reviewing one of the most controversial computers ever built. It is the Talking Electronics Microcomp. The Microcomp is the 3-Chip Z80 single-board computer that was to revolutionise the way we use computers in the '80s. But it was a bit of a flop. On top of this, the creator Colin Mitchell seems to have built this computer to 'outdo' one of his own products! The more successful TEC Z80 computer.
I have revised the board and gone through its history of it, building it and how it works. You can now build your own board if you like!
You can now purchase one (or 5) of these boards. Simple order one from PCBWay. www.pcbway.com/project/sharep...
To complement this video, go to the project page at github.com/bchiha/microcomp. You will find all the information you need to build your own.
I would like to thank Colin Mitchell and Scott Faulkner for assisting with this build.
00:00 Intro
00:50 History of the Microcomp
02:17 Why did I start this project?
02:52 Designing the board
04:54 Things to note when assembling the board
08:53 Assembling the board
09:41 First look and how to use the computer
10:36 Demonstrating the Lower ROM programs
13:59 Using the onboard Probe
15:24 Initial summary and expandability
17:30 My Upper ROM Code and usage
20:44 My final review
22:49 Thank you and building your own
24:07 A computer "before its time"
Links:
Project Page: github.com/bchiha/microcomp
Colin Mitchell's Site: www.talkingelectronics.com/te_...
TEC Computer Facebook page: / tec1z80 - Věda a technologie
Your use of the piezo as a probe reminded me of a former boss that told the story of using an AM radio to diagnose coding errors. The radio had a permanent perch atop the CPU console. Errors and the resulting endless loops they created each had their own distinct RFI signatures when demodulated by the radio.
That's really interesting! Thanks for sharing.
@@ReadyZ80 I did this too with an 8088 system. It was interesting listening to it play edChess, you could hear different phases of move evaluation and it sounded a lot different between a more open position where there are lots of move options and a constrained one where there's not so many good choices of moves to play, but sort of averaged between the players because both sets of moves factor in.
This worked somewhat with an FM radio tuned to 100MHz for my 486 DX4/100.
1967 - My mentor, Brian K. Reid, showed me around the just-delivered Univac 1108 computer. (The University of Maryland had the contract to finish the EXEC-8 operating system Univac had failed to perfect.) The CPU cabinet had four rows of "sense lights" showing memory access addresses. (These were neon bulbs, as LEDs had not yet been invented.) One of these had several turns of wire around it, leading to a radio. It was used for debugging the OS, and to play tunes, and to make rude noises.
"neon", not "me on"
The autocorrupt on my "smart" phone strikes again.
Reminds me back in 1986 at TESC where our senior project was to write an OS for the 8080 chip in assembler. My sub-group did "open file", amazing the things you remember all these years later...
That opening was comedy gold!
That’s a neat little unit and I would have absolutely wanted one but it seems to me that it was quite behind the time in terms of what was going on in computing at that time.
According to Wikipedia, the first Tec 1 was featured in 1983, in Volume 1, Issue 10 of the Talking Electronics magazine. 7 years earlier, Popular Electronics ran a series on the COSMAC ELF trainer that would have provided similar capabilities.
I had an ELF II in 1980 (Hex keypad, 4K RAM, television video output, cassette for saving/loading programs). By 1983, I had a Sharp PC1251 pocket computer with a z80 processor, ASCII keyboard, alphanumeric display, 24K RAM and ROM with a built in BASIC interpreter.
Obrigado por compartilhar esse antigo projeto e reviver o início da lógica computacional, Nesa época era estudante de eletrônica e executei muitos projetos deste tipo. Um grande abraço do Brasil.
Great job. Thanks for doing the board and demo. I started out in computer design from TEC. I thing allot of people owe Colin Mitchell for their careers in electronics. I'm currently building an Omega MSX kit. Might be worth looking up if you're interested in making z-80 based computers. You can get all the parts from Mouser.
Thanks for the reply. Colin's material is still very good for beginners to learn Electronics. I often see it referenced as a good starting point.
Those FM bugs magazines were great!
I remember a particularly interesting device designed for installation into an old landline phone, which would cause the phone to silently answer, when it was rung. Allowing the caller to secretly eavesdrop through the phone being called. I can't remember how it discriminated between regular incoming calls and a spy's calls, but a dodgy device for sure!
I think you would be talking about the 'Telemite' The telephone bug. Published in FM Bugs 1986
@@ReadyZ80 That does ring a bell! Edit: I wish I knew where my old copy was, for the nostalgia of reading through it again. :)
@@beardymcbeardface69 Well, you are in luck. Have a look at the Github page for the Microcomp (see above). In Documents, you will find the FM Bugs magazine!
@@ReadyZ80 Awesome thanks!!!!
The Infinity bug!!
Great wee project and good to test your Z80 chips if nothing else!
What a wildly inconvenient little computer! Seems like a fun challenge to write something interesting for though.
I remember the magazines these circuits would be in. there used to be so many "electronics tinkerer" magazines full of projects like these. Its not something meant necessarily to be competitive with the machines of the day, but rather for an enthusiast or college student to build to learn more.
Thanks for the shout-out!
I loved those TE projects. I still have the FM Bugs mags somewhere.
👍 👍 👍 👍 👍 👍 👍 🍀 CZcams just proposed me your channel. It's very interesting! I keep my fingers crossed for quick development and for sure it's not the last time I visit you (you can keep for mine btw 🤪). Good luck!
Great video!
Bring good memories when I used the famous Micro-Professor to learn Z-80 assembly language. I just wonder how useful will be without static RAM?
I had my two MPF-I-Plus trainers out today. One needs work, a cap started smoking on me. The other one works just fine. :) I also had my Southern Cross and my "The Fox MT-80Z" out and played with them.
I have the entire series of the FM bugs and associated publications and they are awesome!
That's impressive. Although I would always put the 7805 in a free space as people might want to use one of the various switching 7805 replacements (Traco, Recom, etc.). Although it seems kind of weird to put in a switching regulator that probably has more horsepower than the Z80 itself.
Switching regulators rarely contain processors.
@@johndododoe1411 You're right, most of the die of a switching regulator is still the power transistors, although newer ones contain significant amount of logic.
EEVblog has some nice die shots of regulator ICs.
But seeing as even electric toothbrushes incorporate 4-bit microcontrollers nowadays, I would think that it's not too far off, at least for the newer ones operating in the MHz range.
Nice sharing 👍
To bring up-to-date... My thought is to write a version of Tiny BASIC /Dartmouth BASIC for a PIC16F18877, and attach a 1MB serial ROM plus some extra serial RAM to it. In addition to BASIC add a bunch of configuring commands to increase versatility. Make the display at least 5 digits, and be able to display alphanumeric strings (to use for menus).
I choose that microcontroller type because programming it in assembly language is easy enough.
I would use the inbuilt clock, which can change speed up to 32 MHz, and also add a watch crystal so the user can make a nice timepiece with the device .
Total number of chips: 3. .....
If a grid of LEDs duplicates the 7-seg display, then it might be possible to make an 8 X 5 or greater display grid, (with multiplexing more could be added to enable displaying many more LEDs than the 13 signal lines might suggest is possible.). Then it becomes possible to play with serially interfaced accelerometers and magnetometers...
I guess at the end you were relating the board to an early embedded controller? I used to build and program Z80 based embedded machines in the mid 90's, they used the Z-World Z180 derivative of the CPU.
It would be interesting to see if the RAM issue could be fixed by replacing the EPROM with a FRAM (Ferro-Electric RAM) of the same size. This is essentially a RAM that permanently retains its memory. Dividing the RAM up into program space and RAM space would give it more flexibility in using it for tasks that need computational memory.
The FRAM could be pre-programmed with a monitor and then perhaps it could then be programmed by uploading files to it, say under an X-Modem protocol or similar.
The only other thing missing is I/O. Perhaps the LED matrix could be salvaged for driving external I/O...
Anyways a fun little board, thanks for showing it off. Being in Canada I never saw the Australian electronics movement in the 80's, we were mainly inundated with US based tech.
Cheers,
This is certainly possible, set aside a portion of memory for the stack and general data storage area. The Z80 can write to any part of memory regardless of 'writable' status. There is a concept called 'self-modifying code' that will overwrite existing code and execution is different every time. I'll be doing 'Ramless' coding in my next video
What is "Z-World"? Z180 was designed by Hitachi, and originally called 64180. The Z180 is an almost identical processor (family), but with timing and signals more adapted to Z80 peripherals. (The 64180 was externally a little like the 6800 series, that Hitachi also manufactured.)
Z-80 was such an underrated processor. Why almost all of the 8 bit computers went 6502 i don't know. The 6502, while an excellent processor, was very limited compared to a Z-80.
6502, 256 bytes of stack, Z-80 basically the installed memory.
6502 256 bytes of indirect addressing, Z-80 however many you wanted.
6502 1 general purpose register, Z-80 8.
While i liked the 6502 for machine or assembly programming, the Z-80 was better IMHO. Slower, maybe, but you got instructional efficiency you could NOT do with a 6502. The LDIR, LDDR were powerhouse instructions. Not to mention in Inport and outport instructions, which were better than memory mapped I/O of the era.
Sadly, Zilog was not long for the world, but it is a processor ahead of it's time. I feel the same about the 68000 series processors. Better designs, that just never had the market share to win.
6502 was quite cheaper than Z80 or 8085 or 6800. That is why it is selected for Apple II, Nintendo NES and other gaming machines. Microprocessor was the most expensive part of gadget those days. So Cheaper, not powerful one won the competition.
I always wanted to have a play with the 6809 - Tandy Co-co and the Dragon 32/64, but they were out of my price range, and my degree used BBCs and TRS-80s, so...
6502 was a lot cheaper than the Z80. As for your saying the Z80 being slow, a Z80 clocked at about twice the frequency of a 6502 was about the same speed. But both systems would require memory of about the same speed. (Eg. A 1MHz 6502 would require memory that was fast enough to handle a 2MHz Z80). Another advantage of the 6502 was extremely predictable memory access (last half of every clock cycle). Because of this, it was quite easy to design a computer where the video and CPU alternated access to memory. Made for a simple predictable design, and "free" refreshing of dynamic memory.
I’m pretty sure, worldwide, there were more z80 or z80 clone based machines. Granted the 6502 was more popular in the US but that’s not the whole story by miles!
@@johncochran8497 Yep. I was referring to IPC, and the Z-80 was definitely slower when you looked at that. But that was made up for in the fact a lot of instructions just DID more. Sure, the instruction execution required more clocks, but once the opcode was loaded, it could just do more. The indirect addressing was especially tasty, and very flexible. That and just having more registers meant that you weren't constantly accessing memory to swap out data, you could keep some values in internal registers, and those executed extremely quickly, as i recall (it's been a LONG time, so i may be fuzzy on some of the details).
It's kind of the whole RISC vs CISC scenario. The Z-80 was more CISC, and the 6502 was RISC.
And at those clock speeds and memory speeds, RISC actually makes a lot of sense. Just not very efficient in memory use. Nowadays, IMHO, CISC makes a lot more sense.
The diagnostic buzzer is kinda unique concept i think, haven‘t seen that before
Yes. It's a cheap audible oscilloscope!
Things like this are frequently reinvented. I used to use a small speaker, actually one taken from a ZX Spectrum, to debug projects in the 80s. An oscilloscope was too expensive for me at the time. But I only did it because I'd read somewhere of the same technique being used on computers in the 50s.
@@DavidHembrow Certainly easier to my solution to needing something scope like in function as a kid. I'd used an audio amplifier board from something to attain an output level sufficient, either adjusted upwards or down depending upon what I was probing (none of it involved probing relatively higher voltage signals because that was too much work to add functionality for when it was supposed to just be a quick and dirty solution for probing 3.3v and 5v logic mostly, along with messing with audio circuitry like trying to build audio amplifiers myself and messing with shaping the tone).
I ran the output of the salvaged audio amplifier into the vertical and horizontal deflection coils of a CRT with the back off, after disconnecting that from the CRT and then powering up the CRT. Essentially an extremely simplified version of how a CRT scope functioned anyway, without taking into account the many controls a real scope has.
Obviously there were no divisions on the CRT, so I couldn't do more than verify a desired signal was there and that it looked vaguely correct.
It was inspired by a simple design for a home made hobbyist electronics project style probe I found in an 'old' electronics magazine (I say old, I was only born in 89 so)
I would not recommend dismantling a CRT and powering it up to use it for things it wasn't intended when you're in junior school.
Can't help but think that I coulda saved a lot of time had I just thought of doing something like you did :D
Now I feel like making myself an audio oscilloscope substitute. 😊
It's a very traditional feature. It was in the GIER transistor machine from the 1960s, and they somehow programmed notable melodies into the boot code.
Thank you for sharing, also I think Arduino was a open source gate to simplify the world of microcontroller and electronics all togther also C and C++ interaction was very smart move to use it to talk to hardware rather than Assembly, it has encouraged many to use it as before were intimidated by the complexity of machine language my opinion
03:05 good lord, the soldering 🥴🥴🥴🥴
I can't agree that Microcomp was an Arduino of that era. What differs Arduino from that kind of development boards is it doesn't have any peripherals, it is meant to be built in into some other device, or a device to be built around it. I believe this was a key to the success of the Arduino - it could be actually useful, it is not purely educational toy.
I used to use a piezo speaker a lot as a debugging tool back with PIC microcontrollers back in the days of UV erasable chips. I still have some- I need to set up a UV LED with timer to zap them clean!
My EPROM eraser is a phone steriliser I picked up for a few dollars!
@@ReadyZ80 Well done. I already have UV LEDs for less even than that price and can target the window 😊
I like the mreq line sound, utterly relentless, almost as bad as the clock.
Yep. That pin is banging!
The lack of RAM is a serious handicap, but your video was interesting nonetheless.
I don't remember the Microcomp, but I remember that FM Bugs book. We used that book to build our own FM transmitters in my Year 10 physics class. Good times.
(now I'm keen to build my own Microcomp and another slightly dodgy FM bug.. lol!)
I think most of us were teenagers when TE was doing well. I remember making some bugs and selling them at high school. The Microcomp was and is rare.
@@ReadyZ80 Yeah, I was 14 when that FM Bugs magazine came out!
Start building a microbee from the parts Colin gave you.
Anyone remember the CT2 Rabbit phone system that was scrapped many years ago? The base station used an HD64180 (Z80 with serial ports on board chip). using these thrown out boards that included a telecom modem (that picked up an ordanary telephone line to place a charged call) i wrote a simple 4K series of 8 routines in a rom that enabled the boards to remotely load any program you made up remotely into the 64k RAM. The board was in use at a remote building i monitored lighting and heating and power. Z80 code is so easy to write out in HEX on paper that no other language is needed. i use Arduino much of the time now but cant find any way to get an arduino ATmega328 to write its own program in memory. But the Z80 could and eaven read the code back to me to check for errors before run. Security was that you needed the telephone number to chat to the board. Kevin G8RDT.....
Interesting that the development of DIY computers in the USA was the same like in Germany. I did my own experiences in the middle of the 80s. Than the 8051 uC replaces this Z80 for hobbyists.
good evening, where can I buy the assembled circuit?
Another interesting thing about your device is making the display lines do double duty, as either a numerical or a dot matrix (with whichever display is not in use displaying garbage). If this were to be done on a PIC microcontroller which can source or sink 25mA per line or make the line high impedance, with the PIC running at 32 MHz clock, then multiplexing could be accomplished and you could drive many more LEDs than there are available signal lines. For more, search under Charlieplexing... So your device inspires imagination, even if we do not adopt the device itself. :-)
The three outputs, 4x4 Matrix, Seven Segments and Bit Led's are all connected to the same output latch. You picked up that only one of those outputs is valid at one time. But it is certainly possible to multiplex the seven segments and 4x4 matrix at the same time. I do multiplexing on the 4x4 in this video. The clock runs at a max of 0.36 MHz, ramping it up to 4 MHz will make multi display outputting seamless.
Oh wow, this looks neat, I have a free range z80, and probably most of the parts, just no idea how to get the PCB made from PCBway,
Just click here to order a board www.pcbway.com/project/shareproject/The_Talking_Electronics_Microcomp_V2_09a890f8.html
1:06 This is an unexpected place to locate that Vinyl Scratch pony.
Curious how this whets my interest... In the mid-1980s I did a lot of programming, including write Z80 assembly language code.
I also played with a Z8 with a 32K RAM chip attached. The RAM was addressed in such a way that if you wrote into the upper 32K address space the Z80 "saw" RAM, and at the same time it would read the lower 32K as ROM. With battery back up a "ROM" BASIC program could be developed, and if your program was not too big there would still be plenty of RAM available for variables.
Nice...
Makes me want to build a "shadow rom" type system, or maybe modifiable rom?
What DO you call it? Lol.
Cool...
I remember writing some code for a mate who had one of these TEC boards, he wanted it to generate 'Quick brown fox....' serial test messages, boy was it hard with no RAM, what on earth were they thinking - no ram.
They would have been better off with, say a 6802, which has a small amount of ram in the processor.
Someone posted on FB that if you add 'RAM' to this board then its status gets upgraded from 'Useless' to 'Mostly Useless'
The TEC definitely had RAM. It was the Microcomp that decided to reinvent computing by ditching RAM
I think a proper keyboard is essential for every self-respecting computer. The original keyboard of the TEC-1 was odd, the tablesetting of the key was not according to the standard at that moment in time. Bottom row should be 0 1 2 3, second row 4 5 6 7, etc. etc. to make it shot, just like the KIM-1 had it. The TEC-1 had nice things like the adjustable clock frequency and some blinking lights.
What I would have added to the remake of the TEC-1 is an expansion bus, the most practical would have been a standard bus like the RC2014 has. (the S-100 bus would be a little bit to much) When such a bus is present, then suddenly a shortcoming of memory is no longer a point. Pick a card, show it to the audience and put it back in the deck.
Interestingly, my next video planned will be on a full keyboard and expansion plug for the TEC!
@@ReadyZ80 Fantastic. Super!
7:20 - The first thing I noticed was NO RAM! (?)
Lol I'm not even a minute in and I can see the problem.
Does it actually use the latch as temporary storage register?
The latch is used to keep the Segments/LED's persistent (always set) until another OUT command is sent and the data is replaced. You can store 8 bytes on the latch but you can't retrieve it again.
Interesting video. However, I honestly don't see using a Z80 without RAM is going to be that interesting. With a couple of K of ram I wrote a sudoko solver; without any RAM you can just about do blackjack. Interesting challenges are things like, can you break Enigma on a Z80? How about write a neural network deep learning system?
Thank you this thing is awesome. I want to do the same thing for a digital j11. 😂
Heh, that reminds me - I still have my Dick Smith System 80 computer from the early 80's. It was powered by a Z80 as well. I wonder if it still works?
replacement electrolytics, probably.
The system 80 was my 1st computer. Also had a 300 baud modem and modded teletype for a printer. Mind blowing for a young lad at the time. A few dick smith games we had still are not online anywhere so I hope they pop up one day
I wouldn't have thought programs this complex were possible with no RAM and only a handful of registers.
With 8 or so internal registers and their equivalent shadow registers, there is a bit you can achieve with some clever programming.
I might have placed an gap in the soldermask under the tab on the regulator that exposes the groundplane to use it to help dissipate excess heat, but I doubt this necessarily needs it with the kinda load I'd expect it has on the regulator. I just tend to 'over do' things sometimes...well, all of the time :D
Overall, though, this is fantastic! Amazing work to you and those that helped :D
I checked the amps on the 7805 and it's below the need for a heatsink based on the specs.
@@ReadyZ80 Yeaaaaaa, I figured it would. It's mostly just my own force of habit because generally things I do tend to push a lot of power relative to their wee area hehheh :)
omg, Are you try Collapse Os on this?
At 4:00, There are 10 kinds of people ... -- is the funniest joke I have heard in a long time. I am adding it to: A picture is worth 1024 words.
Great observation!
Cool
The PCB looks very new-ish in color and style for a 1985 product. Strange.
See my video on the TEC -1F.
It sounds like you should have made the PCB design large enough to at least accomodate a ZIF socket for the EPROM, given that you need to be constantly pulling it out to re-program while you're doing your code development & debugging.
Funny you say that as the size of the board was partly due to the limitations of the free version of Eagle 😁
@@ReadyZ80 Ahh. Sorry, I missed that point. I’ve had that issue myself, but after years of using various different EDA solutions, I finally decided to make the change to KiCAD for all my new designs. A small learning curve, but after watching KiCAD evolve over the years, I’m very comfortable that it’s now sufficiently mature for all of my current and future needs. :)
I'll have to check KiCad when I have a bit of time. Others in the TEC community use it
No RAM :(
Sadly
I built this when turn on all the lights come on with the 7 segment light on 8. But when I press the button nothing.
Check that the ROM is burnt correctly and I've noticed that some CPU's struggle with the setup.
If it's had a bus connector would make it useful to some kind.
Just to be clear: you need to re-write the EPROM in order to test code? There's no RAM, and no other way to load or save code?
In that case, you need an EPROM programmer as associated hardware.
Yes, every time I want to change the code, I need to pop the Eprom out, put it in a programmer and copy the new code. I used a software debug tool to test before programming and a eeprom to make burning quicker.
And choosing a z80 for this scenario must be the dumbist thing ever. Now if it was a 6800, now that can be quit good, because the 6800/6802 already contains 256bytes ram on board.
Did you write assembly code for z80??
I wrote the menu driver and one of the games. I have a video on RAMLess coding.
@@ReadyZ80 is coding require for z80 cz just askin i am working on it i irdered z80 it will be there soon so is it required for it to code it or it work without code as well
Can it play River Raid ?
If you have any spare mini microcomp board to sell, let me know. I’ve built the original one, and it would be nice to build an updated version.
All out at the moment. I might do another run.
Without RAM or a way to readily run arbitrary programs, it's not so much a computer as an appliance.
Fun board! No ram at all means writing Z80 code is a little more challenging, as you can’t have a stack and so no subroutine calls!
That's right. My next video will be on the joys of RAMless coding!
You can have subroutines of sorts, but not call them through JSR opcodes. Instead you can set a flag, or register with a specific value and then JMP to the subroutines, then use the register or flag to determine where to jump back to. That’s how I did it for my irrigation controller built using the original microcomp.
Five seconds in I'm seeing a z80, an eprom and,.. no RAM. I did a lot of z80 back in the day and 'no ram' is nonsense.
Why? Stick a small sram on there and you have something that isn't an exercise in masochism and makes a reasonable learner 8bit computer
It is briefly cute tho
You should try programming something useful with no ram! I have a video for that. ,,😊
@@ReadyZ80 ... I could try washing the dishes blindfold, or eating an apple pie without using my hands, or riding a bike 5 miles with one pedal (which is a lot harder than you'd think) or...
your audio mix level is too low.
7 Segment Red LED Digital Display Anode or Cathode?
Cathode
A strange computer, but how will windows 10 work on it without a hard drive and hdmi output for a monitor?🤔
z80单板机是我上大学时学的。
I used to have a wife. But I solder.
But no (visible) RAM ...
😔
The big failing is no RAM.
'Diargram'? Interesting spelling.
That's a 4 chip computer.
i think it's in pain. better put it down!
All as it does is play out world war 3 as a game....
First off, hats-off for making this board.
However, a Z-80 without RAM is just so limiting when you want to apply it to real world applications; just never understood why not even a tiny bit was not included. Without RAM, the programming is so clunky and you spend unnecessary time (and extra ROM) trying to make things work. Also, it is a disaster whereby you are trying to collect data (e.g. temperature) to display later.
Finally, the more interesting games, rely on keeping previous states and making strategy calculations… 😊
Don't care.