Memo-1: A 6502 computer built from scratch, using a Minitel as its terminal

Posted by sciences44 6 days ago

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Comments

Comment by zorobo 3 days ago

The Minitel can be used as a modem too, albeit a cumbersome and very slow one: 1200bps down, 75bps up. Bps as in bits per second. That’s how I connected to bbses and nntp before I finally got a 2400bps real modem.

Nice project, and how far we’ve come !

Comment by glimshe 3 days ago

Some younger folks seem to be into all sorts of classic tech these days, like vynil, mechanical keyboards and terminal emulators. But I'm yet to see people giving old modems are try... Probably because there is nothing waiting for them to call anymore :(.

(telnet doesn't count)

Comment by whartung 3 days ago

Not just that, but, as I understand it, with some of the modern digital phone systems, they won’t work properly even if you did have someplace to call.

And 2400 baud was quite useful for a personal NNTP feed.

Comment by johnlorentzson 3 days ago

A pair of smart modems should certainly be able to connect, but it's very likely they would only be able to negotiate a fairly low speed. The classic 300 baud Bell 103 modulation can probably work perfectly fine even over early 2010s Skype. Although possibly with a lot of dropped bits...

I remember dialing into a BBS in the mid 2010s over an international phone call going through a late-stage digital switch locally (possibly one of the later AXE switches but I have no way of knowing for sure anymore), and the call would almost have to have gone through lossy compression on its way to the US.

Comment by iberator 3 days ago

300 baud will not work. arp/tcp/ip have too much overhead even with small MTU.

slip/plip/ppp is workable from 1200 baud up.

Comment by drob518 3 days ago

Yep. Much of the old phone system has now transitioned to highly-compressed, packetized voice running over IP rather than the traditional synchronous SONET infrastructure. While SONET might be used on some links, the whole link is dedicated to packetized data and it’s not carving out a single synchronous voice channel anymore. It’s the lossy compression that will have the most effect on the old modem signaling.

Comment by forinti 3 days ago

I was looking for info about connecting a Beeb to a Linux machine as a terminal, and found this guy using a modem for this:

https://www.youtube.com/watch?v=5QLcx2bvMbA

I'm going with a RS423 to USB cable.

Comment by rbanffy 3 days ago

IIRC the Minitel had a TTL level serial port that’d work at 4800 bps.

Comment by mbanzi 3 days ago

9600 even! :)

Comment by zorobo 3 days ago

Computer to Minitel ttl yes. However the modem part was limited to those paltry figures.

I still have mine in the basement. Maybe its capacitors are all busted…time to give it a spin !

Comment by rbanffy 3 days ago

I think mine tops out at 4800.

Comment by drivers99 3 days ago

Very cool. No surprise when I saw Ben Eater acknowledgement at the bottom. I'd humbly suggest including the CAD (KiCad?) files to go along with the gerbers.

Comment by heretool 3 days ago

Building a 6502 computer from scratch is cool enough on its own, but hooking it up to a Minitel terminal takes it to a whole new level! Outstanding work.

Comment by marsven_422 3 days ago

[dead]