/vr/ - Retro Games

Most extended carts (the type with the extra pins on either side of the main set) are like this. There's just the one spring contact on the cartridge shell.

Doom does have two extra ground pads on the PCB meant to meet up with spring contacts on the cartridge shell, but they ended up only using one because it was sufficient and a second gold-plated contact would have been an unnecessary expense.

The purpose of the extra ground is safety. The demands of the extra hardware in these carts are enough that you can fuck up the cart or possibly your system if your grounding is absent or insufficient, and you could cause that by accident if you pulled out or moved the cart while the system was on. The extra contact ensures the cart remains grounded to the metal shroud around the cartridge slot even while it's being pulled out of the system or jostled by the user.