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Good morning! Welcome back to the ValorosoIT channel and welcome to those who are new to the channel. We deal with vintage computers and electronics. I'm at Varese RetroComputing 2024 with Davide Calvi of RetroEdicola, also known as Dr. Fix. It is the first time on the ValorosoIT channel. So, Davide, what do you want to talk to us about? This seems like a very interesting thing to me.
Yes, good morning everyone! HI! We present the Cosmac ELF.
Cosmac Elf... what was that?
It was a single board computer created by engineer Weisbecker. We are in the year 1976.
Ah, so let's go back in time a little today.
Yes, we are in 1971. Let's start from this year, where the engineer Weisbecker designed the COSMAC 1802 microprocessor. It took a few years, until 1974 to create it and immediately afterwards it was used mainly for industry. Then, since he had a propensity for hobbies and teaching, he took the industrial version, simplified it and became Cosmac ELF. The series was called Cosmac, and added the word ELF to distinguish it from all the others.
So we're talking about this card here, right?
Yes, exactly. It is a single board computer (SBC) where we have the 1802 microprocessor, two banks of 256 byte RAM with 4-bit words. In fact, by adding 4+4, we obtain 8-bit words. A video release that was created the following year, in 1977, and was called 1861.
Ok.
Unfortunately this integrated no longer exists, it is difficult to find, but fortunately it can be replicated with this card made up of PLD and Micrologica.
So we have microprocessor, RAM, video card basically, and all the others are? They are boundary micrologicals.
Ok.
They are used to control the displays, to be able to write and read the bytes written in RAM. This is the clock part and it could go almost up to 5 MHz; in this case it's going to 1.5 MHz, more or less.
Okay. And this is the power supply?
Yes, this is the power part. The video part, the actual output, is made up of this final transistor which then leads to the monitor next to us.
Okay. So is this image that we see generated by the Cosmac ELF?
Exact. This part above is very nice to look at. It is the program that allows you to view graphics.
Ah, so this is the program?
Yes, because the entire 256 byte RAM bank is represented on the screen. So let's see both the code and the graphics.
I understand. That is, in practice, the video card - if we can call it that - therefore the video chip, has access to all the RAM, from byte 0 to 255, and shows them on the monitor. So this might as well be a program, actually. Could what we see now, which is a logo, be a program in theory?
That's right, it could even be a program.
Do we have any other examples we can see?
Yes. Is this your edit?
Yes, this is an additional modification, because unfortunately manually loading 190 bytes, with all the levers, there is the risk of getting even a single bit wrong and having to redo the entire program.
So, the peculiarity was to combine a virtual user, in this case an Arduino, where we can select one of the pre-installed programs and load it.
Oh, okay.
So he's basically now pushing the buttons, as if he were pushing them manually, to load the programs?
Exact.
And here we got one of the games, the one that catches the mouse. The mouse would be this moving pixel, and the trap is made up of these four dots.
Okay. So this RAM here is the program. Could this one that is moving be some counter?
Yes, it's the counter that's moving our pixel.
Okay, okay. This button, which we have combined, is the one that allows us to control the trap.
Now I see... if I can, can I move it for a moment?
Of course, the goal is to get him to end up in the middle.
Let's see if I can do it... did I or didn't I?
Yes, you did, you heard the high-pitched sound.
Ok, I succeeded! What if I let it out by accident?
Let's see what happens...
Ah, it puts you where the error is. He made the point.
Yes, the opponent, the little mouse, scored a point. Oh yes, the little mouse made the point, strong!
We also have another example, which is the target. In this case we have to hit the target. This, let's say, is our gun and this is our target to hit.
It seems more complicated to me. Wait while I try... also because there will be some time between when I shoot. I don't know, did I catch him? It's not clear.
No, because we have the count on the Cosmac: the number of attempts and the number of times hit.
This is harder! I knew it was difficult. I'll never make it... let's see. No, I have to go a little earlier... maybe... no. Oh! Four attempts, zero successes.
Well, as you know, I'm not a gamer, so this is unfortunately what happens.
Here is the scheme. This is the original scheme, precisely the one from '77, complete. Here we have our microprocessor - the CPU - the two banks of RAM, the two displays we saw, the red ones, of the micrologic. This one below is some gates, the famous 8 bits, our 8 switches.
Yes. And these here are buffers that allow you to interrupt the reading of the switches. Because, in execution, obviously there is only one processor. So either it reads the RAM, or it reads the switches. Depending on the need, it will enable reading.
Then, when the program runs, these are excluded, so that it can go and read the program from RAM.
Okay. Over here we have the other switches, which are a little hidden here in the micrologic diagram. The ones we see here. Yes. Charge command. This is the charge command. The command to block writing to RAM. The run command and the insert button. So you select the byte here, do Insert. We can also give it a try. Yes.
And Run. If I press it now, will it go off? Wait, let's try.
Has it turned off? Indeed... but what if I risk it? He starts again.
Oh, ok!
That's right, because if the program stops working, nothing is generated, not even on the screen. It simply stops.
Shall we try to insert a byte? Can you show me how it's done?
Yes, certainly!
So, let's exclude the Arduino. At this point we stop the execution. So basically the memory is empty now?
Yes, it's empty, all at zero.
Oh. Go to Load to load.
Yes, on Load. At this moment we insert FF.
Oh, okay. We see it here, right?
Let's try scaling one bit at a time.
So we started from FF, then each time we removed a bit, starting from the heaviest to the lightest, and we then inserted all 8 bytes.
Exact. So we go to protect the RAM, then Memory protect, we reset the counter and, at this point, if we go to reread, we review.
Ah, we see them all in sequence.
But can we also see them on the monitor?
No, because in this case there is not yet the program that sends them to the monitor.
Right, you would need a program that sends from RAM to the monitor.
Exactly, but it should be added later.
Of course, because it would become almost like graphics.
Obviously at this moment we would do the Run, but we don't even know what it does as a program... they are empty, meaningless commands.
Let's add one last peculiarity: the Weisbecker family. When he finished developing this kit for hobbyists, the Cosmac ELF, the Studio 2 project started immediately afterwards, always starting from the same architecture as the Cosmac Elf.
It was indeed a video game console.
But who could write these video games?
There wasn't a profession yet, it didn't exist. Weisbecker tried with his daughter, who was a 16 year old girl, to have her write some code for this console, and it worked! So much so that RCA liked these projects and was even paid 290 dollars, becoming the first game designer in the world.
Wow, interesting trivia!
Yes!
A thousand thanks.
Again, thanks to you.
Thank you. For those interested in retrocomputers and vintage electronics, subscribe to the channel, activate the notification bell and we'll see you in the next video.
Bye bye!