questions about USB expansion

rangoon wrote: I just built a new system using the Z370 pro gaming i7. I'd like to expand my USB 3.0 options, but not sure the best way to do this. My case only has two USB (3.1) ports on the front, so I'm using one of the internal headers for this. I own an Anker 4-port PCIe x1 3.0 expansion card from a previous build. https://www.amazon.com/gp/product/B005ARQV6U/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 1) in terms of reliability/compatibility/speed is it better to use a PCIe x1 card like the one I have or the remaining internal header for an expansion slot (used to have one for 2.0, assume they still make them for 3.0 - where you connect an expansion card to the header, not PCI)? 2) If a PCIe card like this comes with a SATA power cable (3.3v/5v/12v), is it fine to use a normal molex cable (5v/12v) or do I need to use the SATA power cable? 3) I have nearly a couple dozen USB devices between flight controllers, Oculus Rift, TrackIR, dongles, etc. etc. This board and case don't offer as many ports as I'm used to. What is the best solution to getting more if not either of the ones I've already mentioned? I have hubs, too, of course, but need one near the case, plus two or three others near the keyboard/display area, and don't want to plug too many devices into one port via hubs. I've also typically tried to keep keyboards and mice plugged into their own ports rather than hubs, but perhaps that's no longer necessary (for use in UEFI and general performance without introducing extra lag).

The "best" way to expand the USB 3.0 connections depends upon your goals and usage of the USB devices. Such as, how many USB devices will you be using at one time for a particular purpose. The best way will depend upon what your requirements are for each purpose you want to provide.

You really need to know what each purpose is in detail, and then go about providing the appropriate connections.

General things to consider:

If the USB device has a USB 2.0 plug (keyboard, mouse, etc), connecting it to a USB 3.0 port of any kind cannot increase its performance in any way. All USB 3.0 and 3.1 ports and plugs have extra connections that provide or transmit the increased bandwidth/speed and power. A USB 2.0 plug (or port) does not have any of those extra connections in the plug, so connecting it to a USB 3.0 port is wasting the USB 3.0  port's capabilities.

Your board has three USB 2.0 headers, each providing two USB 2.0 ports (for six total) that can be connected to a USB 2.0 port bracket that mounts in a PCIe card slot on the PC case. The bracket has either two or four USB 2.0 ports, with one or two cables to connect to the USB 2.0 headers on your board. Using a USB 2.0 port adapter bracket would allow you to isolate all the USB 2.0 devices to USB 2.0 ports, freeing up the USB 3.0 ports on the IO panel and PC case.

A USB 3.0 PCIe card like you have is an x1 lane type card. That means it connects to one PCIe 3.0 lane provided by the board's chipset. One PCIe 3.0 lane is 8Gbps maximum. So while the four USB 3.0 ports are rated at 5Gbps each, it is impossible for one PCIe 3.0 lane at 8Gbps to give you more than one 5Gbps connection at the same time. What the actual speed you would get when connecting two or more USB 3.0 devices to the card  depends upon how the card shares the one PCIe 3.0 lane resources between the four ports. Only the card manufacture or testing it yourself can tell you how it would perform.

USB hubs of any kind that only have one USB connection for its input simply share the one input with multiple outputs. The bandwidth of the single USB input is shared or used by one port on the the hub at a time. A USB hub only provides more USB connection points, not full USB interface connections on each port.

Your board has two USB 3.1 Gen1 headers, each supplying two ports, but through a hub chip. You are currently using only one header with the ports available on your PC case. Your board also has one USB 3.1 Gen2 header which may only be for one port. These USB 3.1 connections will be better than your PCIe card, as they share a 10Gbps connection rather than an eight Gbps connection.

The IO panel USB 3.1 Gen2 ports are the fastest ports you have, and should be used for the most demanding data transmission purposes.

Your board's specs and manual describe the USB port capabilities and connections:

http://www.asrock.com/mb/Intel/Fatal1ty%20Z370%20Professional%20Gaming%20i7/index.asp#Specification

A molex connector will provide both 12V and 5V to a USB card, which is all they need. USB only provides 5V, so I'm not sure what the 12V connection to a USB card does, or if it is used at all. A SATA power connector also provides 3.3V, which is not used by USB PCIe cards.