I have a question which is similar to another question on this site:
When I was a child 386 PCs came up. When buying a PC, you could read in the technical data how many 8- and 16-bit ISA slots were available.
Some manufacturers advertized 386 PCs that also had slots that they called "32-bit ISA slots".
I have seen some photos in adverts:
Such slots had a third connector beneath the 36-pin ISA connector (similar to a Vesa Local Bus connectors in 486 PCs); but the third connector had the same appearance (and pitch) as the 62- and the 36-pin connectors and about 20 pins.
(This video on YouTube is showing a sound card which has a similar connector; however, the boards that I have seen did not have 6 additional pins but about 20 additional pins.)
I couldn't find any information about such slots today and I also did not find any photo of a mainboard having such slots.
- It was not EISA; EISA slots are not longer (but the connectors are heigher) than ISA slots.
- It was not VLB; the third connector of a VLB slot looks completely differently than the other two connectors.
- It was not PCI nor MCA; such slots don't have ISA-compatible connectors.
Were those slots manufacturer-specific or was there some kind of (unofficial) standard?
What additional signals were available in these slots?
It makes no sense to me to sell such boards if there are no cards on the market that can be connected to these slots...