Question More PCI Express ... less USB and SATA


Apr 30, 2019
This is an open post to motherboard vendors ... forum comments are encouraged.

With higher end GPU functionality being pushed into the CPU dies (i.e. CPU's that can handle 1080p games with ease), now's the time to revamp the motherboard architecture a bit.

ATX, mATX and ITX motherboards continue to be the standard and there is only so much horizontal area to play with. The big push I'm seeing for systems from most customers and users is NVMe drive expansion options. This means we need more x4 and/or x8 PCIe slots on the motherboard.

I see two ways forward for this:

1. Reduce the number of USB and SATA ports and reconstitute those lanes to include PCIe x4 and where possible x8 slots. Since horizontal space is at a premium in the current motherboard form factors, "going vertical" is the obvious answer via PCIe slots. This isn't a new concept and previously "All" expansion was done via the expansion slots on motherboards (yes I'm dating myself, but why invent something new?). Numerous vendors already make x4 and x8 PCIe boards for additional NVMe drives ... the biggest limiting factor in their adoption is PCIe slots that can support the throughput needed for multiple x4 drives. PCIe slots also support better passive and active cooling options.

2. Implement PCIe Switches. This basically steals a page from the server market, but it greatly expands the number of lanes available and leverages a "switched network" format for PCIe. This has some drawbacks in that you cannot have instantaneous full bandwidth communications with every device, but more often than not, this is not needed and would be a reasonable answer for most data transfer needed. This wouldn't require a reduction in USB and SATA ports, but would require a more sophisticated "south bridge" to handle the switching between PCIe slots.

I see situations where both of these could be adopted with #1 used for lower end motherboards and #2 used for higher end.