The Gigatron TTL Computer without a Microprocessor


In March of 1971 Intel released the very first
microprocessor onto the market, it was called the 4004. This along with 8008 processor released the
following year helped to jumpstart the computer revolution. But does that mean there were no computers
before the microprocessor? Well we know that certainly wasn’t the case
as computers such as the Digital PDP-8 had seen widespread use in business since the
1960s. In fact the guidance computers used in the
Apollo spacecraft were also designed in the 1960s. And let’s not forget the famous story of
Steve Jobs and Steve Wozniak creating the arcade game Breakout which was also made entirely
of TTL logic chips. Of course digital computers were in existence
as far back as the 1940s using vacuum tubes, so needless to say they didn’t have microprocessors
either. In fact, if you think about it, a microprocessor
itself is nothing more than a bunch of transistors, which in many cases can be separated into
distinct sections of logic units. Just as an example, the 6502 processor was
recently recreated in large format with a bunch of transistors and a lot of blinking
LEDs to make it look cool and so you can see what is going on inside of it. They are calling it the Monster 6502. So now I’ll introduce you to the Gigatron
TTL microcomputer kit. This is another do-it-yourself computer kit,
similar to others I’ve featured on the channel before. But the main distinguishing difference is
that this one has no microprocessor. It comes in a very neat looking little box,
and a fantastic manual. I’ll go as far as to say this is the best
manual I’ve ever seen for a project like this. And while it does contain a lot of in depth
schematics and stuff, don’t let that scare you away as the assembly instructions are
actually really simple and anyone should be able to assemble this. In fact, the only tools you’ll really need
is a soldering iron, preferably a good one, some rosin core solder, and a pair of wire
cutters. And that’s it. So, just taking a look at what it comes with,
here’s a bag with most of the smaller components. And here are all of the TTL logic chips, along
with a RAM chip and an EPROM. This appears to be a ubiquitous USB power
cable. And this is the board itself. The layout on this board is spectacular and
I can tell a lot of attention was taken to make this look nice and be easy to assemble. And down in the corner it says The Computer
without microprocessor, along with the main specifications. I’m going to follow the assembly instructions
in the manual and it says I should start by installing these 40 little capacitors. And so that’s what I’ll do! There was a little confusion in the manual
on how to install these diodes. I had to read it several times. So, hopefully this is right. Well, the manual says at this point I can
power it up, and if I see the test pattern flashing on the LEDs, then everything is working
so far, and it looks like it is. So I guess I got the diodes in right. Next, I’ll install the audio output. And we’ll need the joystick port. And the last thing is the VGA port, along
with the various circuitry that goes along with that. After spending many hours assembling this,
it was time to actually test it for video output. So, crossing my fingers. Hey it works! So for final assembly, I just need to install
these rubber feet on the bottom of the case, and then 4 more rubber feet go inside the
box at the corners. The board actually rests on these. And then I can just insert the board and close
it up. It’s definitely a thing of beauty! Well, let’s see what we can do with it. When you first power it up you get a menu
of some test programs you can try out. I’m going to start with pictures. Interesting.. some kind of ape. I’m not sure which species. Anyway, the Gigatron can display 64 colors
because it has 2 bits for each of the RGB channels, which I noticed when I was soldering
in the resistors. And while the resolution is very low, the
colors are actually quite nice. So let’s talk about the video display a
bit. The Gigatron can display a video resolution
of 160 by 120 pixels, which is less than most 8-bit computers. However, the Gigatron doesn’t really have
a video chip. They’ve borrowed a page from the Sinclair
ZX-81 and all of the video generation is handled in software by the CPU. Of course, in this case, I use the term CPU
somewhat loosely. And due to the clock speed of this machine
compared to the speed of a VGA signal, 160 pixels is the best resolution that can be
made. If you’ll notice, every 4th scan line on
the screen is black, giving it a sort of retro-appearance, however, part of the reason for this is that
during the black scan line, the CPU is free to actually execute code instead of worrying
itself with drawing screen data. However, it is possible to disable this feature. But first I’ll show you the Mandelbrot demonstration. So this creates a fractal image on the screen. It looks like it wouldn’t take very long,
but this actually takes quite some time. But one thing I wanted to show you is if you
press the SELECT button on the controller, it will toggle the scan lines to a more full
looking mode, at the expense of losing CPU cycles for program code. And this is clearly obvious on a program like
this because you can see how much it slows down when this mode is enabled. Even in the faster mode, it takes almost 20
minutes to draw out this fractal pattern. There are a couple of games on here, the first
one is snake. And I haven’t entirely figured out the point
of the game. I’m not sure if I’m supposed to be collecting
these dots or avoiding them. The other game is called racer. And I think the point is to simply see how
long you can go without crashing. So I want to take a moment to talk about the
programming language for the Gigatron. The CPU, if you can call it that, only supports
8 instruction codes. By coincidence the PDP-8 was named what it
was because it only supported 8 instructions as well. Even an old chip like the 6502 had 56 different
instructions and processors from Intel at the time had hundreds of different instructions. Writing code with only 8 instructions is certainly
possible, but would be very tedious. And so what they have done is created a virtualized
environment. So, imagine for example, if you look at how
computers were done in the 1980s, like an old Apple or Commodore, and if you imagine
the hardware layer, this is the actual CPU itself, which must be programmed in machine
language. Then they wrote a BASIC interpreter that is
written in machine language, but allows a BASIC program to run and a more friendly environment
for the user to operate in. Well, the Gigatron does something similar
to this. It also has the hardware layer, but then a
virtual CPU is running on the hardware, which is written in the native machine code, but
it interprets the user software which is written in something called GCL, which stands for
Gigatron Control Language. The language is still very similar to assembly
language but it does at least have 34 instructions making it easier to code for. You might compare it to Steve Wozniak’s
Sweet 16 language in this regard. The CPU runs at 6.25 mhz, but by the time
you take into account this virtual system you’re probably getting something closer
to 1 MHz which is more similar to home computers from the 1980s. So, while the Gigatron is pretty cool from
a proof of concept and from an educational standpoint, it does have some flaws, which
I’m going to have to point out. For one thing, it’s not cheap. Now, computer manufacturers figured out a
long time ago that the way to make computers cheaper was to reduce the chip count, not
to increase it. And so, this computer with the number of chips
it has, and the size of the logic board and all of the different holes and traces on it,
means its not cheap. It retails for 160 Euros, which at the current
conversion rate is almost $200 US dollars. And that in and of itself wouldn’t be so
bad, except the second problem. And this is of course, just my subjective
opinion, but the truth is, once you’ve finished assembling the computer and you’ve explored
all of the built in software, there’s not a lot you can actually do with it. There’s no way. There’s no keyboard interface and there’s
no way to actually program the Gigatron from the computer itself. There is a feature called loader on the main
menu that will load new software in, but it requires using an Arduino and of course doing
all of the coding on an actual modern PC. And so I think that’s a big drawback, and
thus loses a lot of the fun that could be had from experimenting with it. However, that issue is mainly just a software
issue. And who knows? They could update the firmware at some point
to include some sort of command prompt, maybe even run BASIC or at least some kind of machine
language monitor. So, is it worth the money? I guess you’ll have to decide for yourself. Myself, I’m just happy I was able to show
you the product because I do think it’s pretty interesting and I hope you found it
interesting. However, I’m still hoping somebody will
build my dream computer. And rather than go into that here, I’ll
put a link down in the description to an article on my website showing what I think my dream
hobby computer would be. And maybe somebody will build it. So that about wraps it up for this episode. So stick around until next time and as always,
thanks for watching!

100 thoughts on “The Gigatron TTL Computer without a Microprocessor

  1. I love your videos. I stumbled upon your channel looking for good info on CPU technology, can't stop watching. I kick myself for giving up all the Commodore stuff I use to have!

  2. dude, it's a MANDRIL, lol you obviously know more about computers than you do about notorious animals species

  3. I built my first electronic 'computer' in 1968 using VERY expensive new SCRs and NPN transistors, with 4 flop 'gates'. Didn't have fancy ICs back then…

  4. But to be honest the whole lot is a microprocessor its just not in one chip yet.

    You could say the same about transistor or diode first computers with wire an punch cards

  5. Man, I'm tired of gigahertz speed computer parts, flash memory, PCIe slots and all this other contemporary BULLSHIT. Take me back to the GOOD ol' days when computers were SIMPLE.

  6. Mandrill. That particular photograph was famously included in the Amiga demos. In fact all of those pictures are from the Amiga.

  7. dude i love you! really!! but who tough you how to solder? you never solder chip sockets on to a board with the chips plugged in! why do you think we have chip sockets!!, also just a commendation, rather then separate 2 pin components leads, twist them together instead

  8. 2 bit guy . No really this thing asks at what point do you break the rules and make something out of totally low level parts. In this case it is really only the DRAM that is a LSI chip. That is probably better since it is a mostly irrelevant part of the computing process. They chose not to have a GPU.

  9. Since this video was released, there is a ps2 keyboard interface included with the board. Which would indicate that it is evolving in some manner.

  10. 160 EUR "not cheap"? Hahaha, you really have your priorities month/day/year! This is a beautiful piece of technology and also a fantastic gift. The price is well appropriate.

  11. Just one word. Atari 5200 arcade home video game and computer console. Only they never released the keyboard that was to interface with it. And the blank rrw cartridges that were to compleat the storage part of the home computer part of the game console . Timex synclare with the texas instruments z80 processor and Commodore 64 came out almost at the same time and was better and more versatile and powerful. Not by much though 😎 however as a game console alone it was a superior unit the analog to digital converted joystick and trackball and automobile controlers were better than all the other video games on the market for many years after and even to today. Most games joystick have only push button controlers with no true analog joystick, or the analog stick is verry small. Meaning you have to buy an expensive aftermarket joystick if you want a good true analog stick for things like flight simulators etc… love the old 5200 It's a classic collectable early top notch video gaming console with true arcade grafix that are great even by todays standards.

  12. Did I just saw a glitch in the Matrix? At 1:49 the left page is being filled with content after it first appeared half-empty.

  13. I want to frame that Monster 6502 on my wall.
    Micros upgraded my whole thinking.
    It's like a whole new sandbox once it starts to all click in your mind.
    I can't stop talking about em because they are everywhere and in everything.
    I love teaching how to use them.

  14. This actually seems like a really cool project to do in your spare time while youre watching TV or something. Just kind of sit back, relax and build a computer lol
    Maybe it's just because growing up I always thought circuit/motherboards were the coolest looking thing ever. They just looked so advanced and amazing to me and then I learned later on in life that they are actually relatively simple once you know what everything is.

  15. O chato dos computadores atuais é quando eles pifam a gente é obrigado a comprar outro. Não há quem troque os componentes ruins por um preço razoável.

  16. This Guy is a TRUE NERD. But I love Your channel showcasing old tech.
    You want a dream computer built? contact CareyHolzman's computer channel here on YouTube.

  17. I would have integrated an Arduino Nano socket or actual Arduino Nano compatible into the thing so you could at least have fun developing on it.

    And a mode that removes the Virtual CPU layer so you can develop straight on the hardware too.

  18. U got to install all the resistor n extra onto ur board? 😳😳 I want that. Where did u get it? I even do not care what it is I just want to set up one.

  19. Мне нравится этот проект. Думаю, я бы сам это легко спроектировал. Серия 74НСТ неплоха, но я бы собрал ее с тактовой частотой 50 МГц на 74AHC и 3nS чипах памяти) Проект уложился бы в 1к рублей "с ушами". Какие ещё 200 usd =)

  20. Amazing, very nice design. And the designer knew his classics by labeling the LEDs "Blinkenlights" at 5:00. Good that there is a transparent cover to avoid gefingerpoken und mittengraben!

  21. I've built this way ZX Spectrum 48K clone back in 1996 (produced by a local factory in exUSSR). Bought all bits and pieces on the open-air market. It was a lot of fun.

  22. If you haven't yet, you should check out Ben Eater's channel. He walks through the process of building a programmable 8-bit computer pretty well from scratch.

  23. They could print that in a 3D printer, and possibly even be printed as a ball or any 3D shape.
    The motherboard with no cpu printed in a 3D figure with a 3D printer.
    Just with more ram memory and in an M.2

  24. I hope you mean that the Intel 4004 was the first microprocessor that was marked to the public !?. Because there was, at least, two microprocessors there were designed and produced before the 4004, The very first was the MP944 that probably never made it to a civil product and the second was the TI TMS1000 that was not publicly available before 1974 🙂

  25. 7:04 no no, it does have a central processing unit, a CPU. Its not a microprocessor, but the name CPU was used long before microprocessors were invented. They usually took shape of circuit boards just like the one you have of course.

  26. I very much want two or more Gigatron TTL Computers , I hate "Pay-Pal" "Bit Coin" and I am very uncomfortable with "Bank Transfer"

  27. I've seen those people who said "Build computer without ….". So I am giving you even harder challenge. Build a computer without using WIRES.

  28. A cool kit ,i like it,i will get 1 of these.it maybe expensive.but its the enjoyment of building it ,and seeing how it works.plus learning how it works.without a microprocessor.like in the coments ,cpu's were around before microprocessors.another tip.is too use sockets,on the i.c.s.we know most are cheap logic etc.but sockets cost pennies,cents now.damn sight easier too remove.if an i.c.dies.just pullout and replace!i always use sockets.on my projects.plus early dip i.c. computers,mainly used i.c. sockets for this reason,and chip cost.i.c.s were expensive.in the 1970s,1980s.it was an idea carried over,from vacuum tube computers.easy too repair .pullout ,pushin!

  29. this is very cool……. thanks for the long hours of editing and late night dead lines….. i hope you feel accomplishment and value in your work because i am enjoying it…

  30. this confuses people, it's just a video game with a "microcontroller" inside, the parent microprocessor which is used for PCs and smartphone.
    but it is mandatory to learn as the basic architect of computer hardware and programming machine leanguage

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