It would be something a bit like this: https://www.ebay.com/itm/115721630079

Before Thunderbolt was common, people attempted to use external GPUs with this sort of expander, but it worked really poorly.

I did this back when, just using a 100mbit NIC express card.

Ran openbsd for a few years like that, the base OS included everything needed. I recall it used 24MB of ram and closer to 30MB if ssh'd in. It was very handy to have a local login when playing with firewall rules.