These computers are probably the second most recognizable format. They are popular for gamers, and typically the only kind that do it yourself PC builders can build for. With that said, the case itself only has a few requirements with most things falling on the responsibility of the motherboard manufacturer.
The actual case itself must support two 5.25″ external drive bays. One bay could be for the blu-ray writer, and the second can be for a second optical drive, or for a hard drive caddy. The case must also support a UHS3 SDUC card slot. This will allow for transferring of files without requiring a LAN? connection. The internal drive bays must be able to support four 2.5″ drive bays for SSD?s. The system should have adequate air flow to keep the system cool. All cases must be tool-free for its design. This is to reduce the number of items it will be needed to do a basic cleaning, or replacing an item. Last, the case must be able to support one 2 slot GPU system which the GPU must be on the top of the PCIx slots, and 2 PCI-X1 slots for future upgradability.
The motherboard must support 6 USB4 speeds, and connection. This requires USB-C connections since this is the only acceptable one for USB4 standards. There must be an HDMI port for connecting to monitors or TVs. An RJ45-1GBPS port must also be available. There must be a minimum of 2 SODIMMs, and two 2280NVME modules. Since the case is required to support 6 devices, then the motherboard must have 6 SATA connections.