I have on my desk an older AGP card, an Ethernet card and a TV tuner card. All of them have an empty DIP socket. What is this supposed to do?
A lot of ethernet cards had an option for a boot ROM to be installed.
On any PCI card, if you provide the right digital signature, an installed ROM will be read and executed when the machine starts up. The AGP card may have had an optional video BIOS available and the tuner card may have had some other similar type of option available.
It’s also possible that the card was designed to take DIP or some other type of EPROM chip, with one or the other installed depending on whose chips they could get at the lower price.
The above is most likely correct. I will note that I have also used dip sockets as test connectors, as they have fairly high pin counts, Don’t increase the height, and are cheaper than about any other type of connector, and you can get (or used to be able to anyway) DIP IDC plugs for ribbon cable.