Clint made a video about one: https://youtu.be/Q4qJf50YSVk

You need a Backplane wich is basically just some ISA Slots in a row. The Backplane usually has some power input.
Dont put them into normal Mainboards!

Yes they are for industrial applications (controlling production machines or processes) where a quick swap of components saves you a lot of money because of less downtime.

Backplanes are available in enless configurations. AT ATX. With ISA, PCI, AGP (PIAGP) , PCI Express... Depending on your CPU card you can choose the right backplane.

This is a backplane for ISA/PCI combo CPU Cards (center slots). The 2 busses are brought out to regular Maniboard dimensions.

The bus is just an extension and can be used like a normal (in this case) ISA bus. The Card also has a PC-104 Connector for special industrial cards. PC-104 is Just ISA but with Pin headers.
https://en.wikipedia.org/wiki/PC/104

I have a collection of different Industrial CPU boards and Backplanes. Its really fun to play with them.
Usually they are high Quality and pretty compatible (because Industry).

This is one of my CPU cards. I just love them...

Here is another example with just PC-104 connectors.
Its also a Single Board Computer and right next to it is a PC-104 Card (Can-Bus controller).
I usually get them for pretty cheap because people dont know what it is.

Hi there!

I'm no expert, but I think you're right.
The computer card is heavily limited by the ISA bus.
That's why most important I/O ports like IDE/SCSI, floppy and maybe ethernet are on the card itself.

That way, the ISA bus isn't being slowed down and freed for its main task.
And that task is interfacing industrial or scientific controller cards, I believe.

Because, if we look the other way round,
then these single board computers do lower the burden of the ISA.
So from an controller card's point of view, it's not ISA that's the bottleneck.
It rather is the standard PC that usually takes away the bandwidth from it.

Another feature of such a "PC on a card" is its serviceability, also.
It can be removed and "upgraded" (replaced) in no time.
All the expensive ISA cards can stay in the backplane.

But yeah, I know it seems still wasteful.
A PCI card seems more logical. And they exist, also.

But there's a problem. Professional cards atnthe time were often made inhouse, with discrete parts.
A stident or prof at an university or lab had the know how to design an ISA card with bare hands and a vero board (a bit exaggerated, I know).

Likewise, PC magazines of the 80s and early 90s did publish photo copies of ISA card PCBs for etching at home (mostly 8-Bit cards and single/double-sided).
Not so much for PCI cards, if at all. Like USB vs serial/parallel/gameport, PCI was less used by tinkeres.

Because it needed a special bus interface chip.
By contrast, a few discrete, 1970s chips for address decoding was all it needs for ISA.
With them in place, it's possible to drive a transistor, relay, lamp by merely flipping the status of an i/o port.

Awesome to know! Thank you all for enligtening me on this little query of mine. I'm going to take a look at that youtube video RandomStranger posted above!

Jo22 wrote on 2022-08-15, 14:52:

The computer card is heavily limited by the ISA bus.

they're really not limited by the ISA bus for their intended applications, the reason why many more modern SBCs still exist with ISA only is because exactly what you said, easy servicability, a lot of industrial machinery that was built in those time periods uses ISA control cards or the like, and in case of a hardware failure you can simply swap the SBC and keep using the machine.
and ISA is just fine for that and really robust.

high graphics or storage performance isn't really a focus of these, that's what other dedicated servers/workstations are for.

but they evolved just like any other PCs
it's just that in industrial applications like that long availability for parts is important, so older buses like ISA just stick around longer.
but SBCs are available in ISA, PISA (PCI/ISA), PICMG 1.0 (PCI/ISA), PIAGP (PCI/AGP), PICOe (PCI/PCIe), PICMG 1.3 (PCI/PCIe), or just PCI or PCIe and also some proprietary formats

apart from the form factor it's really not that special, it's just a highly integrated motherboard in a smaller form factor with an edge connector instead of dedicated slots for other cards with the backplane providing the slots.

and then there's the even more compact PC/104 that also has newer standards like PC/104 plus with PCI or PC/104 express with PCIe

I find the world of industrial/embedded boards very intruiging and they're very fun to tinker around with 😀

I also collect them in all shapes and sizes 😁

Yeah I actually showed this to my Dad he is a CNC machinist by trade, and turned out alot of the machines at his job use these so its kinda cool to chat a bit about it with him some! Though he doesnt do any of the IT stuff 🤣