What is this Intel 8080 thing anyway?
Вставка
- Опубліковано 23 сер 2024
- Intel 8080 CPU, dual Shugart drives, RAM, ROM, and a serial port. It's a computer, right? Well, let's try to figure out what the heck it actually is.
Twitter: / talesofweird
Instagram: / talesofweirdstuff
00:16 Intro
01:45 System overview
04:26 External connections
07:13 Plan to dump the ROMs
09:58 2708 EPROMs are painful
12:06 Sketchy 2708 reader
15:33 The ROM dumps!
19:51 Closing words
GitHub repository containing the ROM images:
github.com/ian...
A very sketchy way to dump a 2708:
www.pinwiki.co...
A less sketchy way to dump a 2708:
museo.freaknet...
After rewatching the video, I realized that I never said that I verified that the EPROMs are 2708s before attempting to read them as such... and people have rightfully called me out for it. :) I just added a picture to the GitHub repo linked in the description showing that at least one of the chips is a 2708.
I believe it was a "stand alone" disk duplicator. Loved the video!
That's... interesting. I hadn't even thought of that.
Good luck, here's a like!
An actual suggestion: you mentioned being in Portland (possibly Oregon)? If you are, Adrian Black is in the area, and he's mentioned in the past that he has an EPROM reader that can handle older chips that do require other voltages. Maybe you could get in touch with him and see if he could try and dump the ROMs in a less hacky method.
Adrian and I have met. :) I loaned him an Atari ST that he used in a troubleshooting video back in September 2021.
We do have some veriacs for sale at surplus gizmos for cheap right now which is great for slowly adding power to some of those older power supplies, as you don't want a sudden inrush of current on those caps. The caps likely need to be reformed.
I almost bought a (vintage) variac a couple months ago... I didn't know what I would use it for, and someone else was interested in it. I let the other guy get it. :shrug:
I've seen some crazy work arounds. But I think this one takes to cake.
No kidding. I will have to build something less sketchy before I try anything like that again.
If it were Adrian, he wouldn't have worried about bending the pins (heck, he'll CUT pins), but he would've done what you did, just because it's easier, especially with 8 of them. I just wouldn't assume any or all of them were 2708. I'd try to trace the sockets to see which pins had power and ground and try to determine what power the PSU would generate. And if they matched the 2708, then I'd be comfortable applying the power and trying to read them.
I Adrian's defense, I've only ever seen him cut pins on chips that he was reasonably sure were already defective. As for the 2708... I just added a picture to the GitHub repo linked in the description showing that at least one of the chips is a 2708.
Hello! Have a great night. Stay chill and hydrated.
These P8251 "Asynchronous Serial Controller" and English words in clear in some of the ROMs, making me think that it possibly could work autonomously commanded via the Serial Port and, as @tomknowles8979 suggested could duplicate disks (no point on reading/writing disks via serial with ASCII responses in the ROM). Does this supports dual usage as a floppy drive and duplicator (given the ins1771d-1 that could do both and at least two lines from it go to the P8251 using the Data Access Lines bus, sorry, I cannot see more ) ??? And a big thank you for not bending the pins 😁 BTW, the Retro Chip Tester would read them 😉
Yeah... there was no way I was going to bend those pins up on 6 chips and solder wires to them. Madness! I didn't even thing of the Retro Chip Tester. I have one of those, but I think I'm missing the module that lets you dump ROMs to MicroSD. I know some other folks in my area that have all that, so I might borrow it.
Try 'xxd' over 'od -t' for initial viewing of dumps, I find it a little easier to spot things at least.
I often forget about that program. Thanks for reminding me. :) I do like the way it mixes hex and ASCII.
I did see something similar or this kind of computer. it was a littleboard, which I ended up selling. it could be a custom job or a kit company that just dried up. 77 was before my time, but I heard it was a very wild west era for personal computing.
That got me thinking... Byte magazine existed back then, and they covered a lot of unusual things. I wonder if this thing might have appeared in some issue of Byte in the 77 - 79 time period.
Looks like a line printer interface
It's not impossible... but I would have expected some text in the ROMs related to printing. Maybe those other ROMs didn't dump properly, and there's some missing clues there?
Can read that in vintage data I/o programmers
I've passed up several opportunities to get vintage EPROM programmers because I didn't think they had any utility. Now I know better!
Dude, the pcb only has 2 power wires going to it, so how would it supply +5, -5, and +12 to the EPROMs without some kind of on-board switching supply? I suspect you have 2716s, and hopefully you didn't smoke them with the 12 Volts. Why wouldn't you try that first before being convinced they were 2708s? 2716s came out in like '77 and the tag said 1979 on them.
There are a couple loose wires from the power supply that were presumably connected to the board at one time. I peeled back the label on the ROM labeled 6, and it said 2708 on the chip. I thought that was pretty convincing. :)
@drozcompany4132 I just added a picture to the GitHub repo linked in the description showing that at least one of the chips is a 2708.
If you go back and watch your video stream you should be able to figure out which ROM goes where.
About that... :( That was my plan. However, between my camera overexposing and OBS recording at a low bit rate, I can't actually read any of the labels. I can tell which ones are 5 and 6, so I have a guess which order the other are.
I cast my vote for it being a stone age word processor. 🐵
Like with the suggestion that it might be a printer interface, it's not impossible... but I would have expected some text in the ROMs related to word processing tasks. Maybe those other ROMs didn't dump properly, and there's some missing clues there?
@@TalesofWeirdStuff Well, I did say stone age. For example - I've got an old IBM Wheelwriter from 1986 that has some super basic word processing capabilities like saving blocks of text in memory then playing them back with a key combination. But anything is possible! I'm curious to see what it does when you're able to plug in a console and fire it up. ^_^
You can dump roms with arduino, and it looks like you have a problem with an upper address line causing code duplication.
The EPROM programmer that I was using only had 2716 (2K x 8), so it just read the 1K x 8 ROM twice. I made some updates to the video description... I found an (old!) article about dumping 2708s with a PIC, so I suspect the Arduino circuit would be very similar. I may have to give that a try one of these days too.
You also need a limiter :D
Data recorder
I'm imaging a flight recorder box where the co-pilot has to change the floppy every few minutes. 🤣