2

If I have a 20/19 pin header on a motherboard or pci-e expansion card, how many actual usb ports does this support?

I've seen most recommend 2 ports per header.

However, a product like this would seem to support 4 ports with one header: http://www.tendak.com/index.php/Product/show/id/116.html

Chris Weber
  • 1,265

3 Answers3

6

Intel had defined that header as providing two USB 3.0 ports. There aren't enough pins for more ports.

http://www.intel.com/content/dam/doc/technical-specification/usb3-internal-connector-cable-specification.pdf

From page 8 of the spec linked above:

2.1 Signal Descriptions and Pin Assignments
[…]
Figure 2-1 illustrates the USB3 ICC pin numbering. Note that the connector include[s] two USB ports.
[Figure 2-1 shows a 19-pin header connector pinout]
Users may choose to include more or less USB ports by expanding or reducing the pin and wire counts. This document covers only the base unit with two USB ports.

That product you linked to apparently has a built-in USB 3.0 hub (or two) to allow it to provide additional ports. The site even calls it a "front panel USB hub".

Spiff
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1

The 20 pin usb 3.0 connector socket passively allows two usb 3.0 female type A sockets two be wired in...

With the use of active "hub" you could split these 2 physical connections into multiple connections... But as with all active adaptations... Latency will be introduced; you'll be introducing a "middle man" (or you know another PCB) between your usb 3.0 devices and your motherboard...

Sticking to the physical limitations of your motherboard and running only 2 x usb 3.0 females type A to every usb 3.0 20 pin female motherboard socket will yield best performance...

Charles Stawell
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-1

The usb 3 header can provide 2 usb2 headers. Therefore a usb3 header can provide 4 usb2 ports or 2 usb3 ports without a hub.

philhu
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  • no it doesnt. A usb3 header can provide 2 usb2 header, which then allows 2x2 or 4 usb2 ports. Where did anyone say that before? I know it is true, it is a cable only, no hubs and works fine. MODDYI sells it – philhu Mar 23 '18 at 15:45
  • Source for the 2x2 claim? It is true that a normal USB2 header would support 2 ports, but a splitter isn't exactly the kind of "usual" thing you could apply common wisdom to. I do have one myself for instance (it's for USB2 by MZHOU, and not modDIY, but still) and while it can "merge" two physically different cables/sources.. you'd better hope none of them offered/used two ports because only one will work on each end of the Y. Then, I'm not an electrical engineer, but the spec seems to suggest similar behaviour to USB3. – mirh Apr 03 '23 at 22:33