A disstraction so you don't look at the barrel battery? 🤣

Hah, good one! 😁

Seriously, though, that could be a proprietary 32-Bit slot.
Some 386es also had them (for memory boards, etc.)

Well, that was my first thought as well, but again, on a 486 with on board SIMM sockets?

Though now that I think of it, I've seen it on a Compaq that I used to own, but the proprietary slots were different. It was a PCI/MCA style slot on the end with a 6 pin ISA style slot further back.

Another glance at the picture with the LIF socket suggests it is an older 486. I missed that the first time around.

It's so when you want stereo Adlib cards you can throw them in back to back.

Jk. My thought is a proprietary system bus. Maybe some special multimedia function advertised as part of an OEM deal.

Basing my answer on this page, it's probably a 32-bit external memory card slot - maybe similar to this one.

It's most likely a memory expansion interface. You can see traces from it snake its way to the SIMM slots. Looks like it's compatible as a normal 16-bit ISA slot too, since you see the left side of the 16-bit connector being tied up with the ISA bus.

Moogle! wrote:

Well, that was my first thought as well, but again, on a 486 with on board SIMM sockets?

Though now that I think of it, I've seen it on a Compaq that I used to own, but the proprietary slots were different. It was a PCI/MCA style slot on the end with a 6 pin ISA style slot further back.

Another glance at the picture with the LIF socket suggests it is an older 486. I missed that the first time around.

Some boards, like the Asus ISA-386C, have onboard SIMM sockets but also options for an external memory card.

http://arvutimuuseum.ee/th99/m/A-B/30218.htm