I never worked with DOS BBS systems, so I can't say about this photo specifically, but the ones I did work with had between one and four dialup modems hooked up to each machine, depending on its capabilities. They did "networking" through a store-and-forward messaging system. It wasn't networking as we'd recognize it today.

IBM had a network that ran over phone cords that were daisycbained from one node to the next.

I knew a couple of local DOS BBSes that ran multiple lines with PCBoard under DESQview.

[^1]: e.g. https://en.wikipedia.org/wiki/Diversi-Dial

Edit: Ugh... I'm gonna have to go back to floppy images to find it. There's a "MUBBS" for Mac from 1992 showing up in search engine results but that's not the one I'm thinking of. It was more like 1989 or 1990.

You can have a second computer once you've shown you know how to use the first one.

-- Paul Barham, quoted in the COST paper

maybe i'm a bot.

anyway i used to call into BBSs back in the early 90s and the thing I'm remembering is that they survived mostly on donations, and now that I am seeing the infrastructure that supported those systems and recalling the price of hardware back then I'm starting to second guess everything I thought I knew.

That seems odd to me, too, because before DOS and the Commodore 64/Apple ][ era, multi-user systems were everywhere.

Not just mainframes and minicomputers, but there were many dozens of multi-user systems based on CP/M, MP/M, and other operating systems. Even Tandy had them.

The revolutionary part of the "personal computer" era was that it was your "personal" computer. You finally didn't have to share it with anyone.

Really Cool Kids T3s...

That said, I have no idea how a multi-node BBS would work, in terms of keeping state synchronized.

Access to knowledge, equipment, and budget varied dramatically prior to widespread internet access. Someone setting up a BBS might not even know about multi-line modem cards or serial port expansions. Even if they knew about them they may not have been able to reasonably obtain them. Or they may have been operating on donations, surplus, or discount equipment. Or they simply may not have had the luxury of time to research all of that as user demand meant they were too busy laying tracks in front of the train.

Many BBSes ran on 1-2 lines per PC because that's what they understood how to build or the hardware they had access to. You might be surprised at just how many lines some BBSes setup this way had!

People forget there was a time that anything outside the standard PC was extremely expensive, often had flaky or nonexistent software support, locked you into a fly-by-night vendor that might go out of business tomorrow, was only available via a distributor who wanted to have you talk to a "sales consultant" before they'd sell you something, etc. Many many people chose sub-optimal implementations because it was an off-the-shelf PC they could replace at any time with trivially simple software requiring no special CONFIG.SYS drivers or TSRs to fiddle with. Especially if you'd ever been burned previously.

She had no idea who these people were or why they were upset. I don’t think I copped to it, it was not an easy thing to explain but I did not do that again.

Our ddial was a few towns away so we bought a line in the exchange in between that would forward to the ddial. This way we would not pay a bunch on long distance calls.