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On my Gigabyte 880GM-USB-3 motherboard there are 2 USB-3 ports. Drivers are installed successfully in Windows 7 OS.

USB-3 ports are working properly when any USB-3 devices are plugged in e.g. USB-3 Pen drive. However I notice that when it comes to USB-2 devices only my usual USB-2 pen drives & Pointing device like Mouse are detected when inserted in those USB-3 ports.

My Android KitKat OS Phone’s internal SD card is not detected at USB-3 port when phone is attached by its USB cable and also my TP Link TL-WN721N USB WiFi adapter is also not detected at USB-3 port. Such devices work just fine when connected to USB-2.

That makes me wonder if USB-3 is really backward compatible with USB-2. Are there any design requirements or constraints that result into certain USB-2 devices just not working when connected to USB-3 ports?

Should I leave it here as 'behavior by design' or I need to troubleshoot further why these devices don't work when connected to USB-3?

Thanks.

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    USB 3.0 ports are backwards compatible with USB 2.0, it is part of the standard... I have an HP notebook which only has USB 3.0 ports (no 2.0 ports at all) and I have had dozens of USB 2.0 devices connected, including TPlink TL-WN721N and WN722N adapters, and cell phones back to Gingerbread, with no issues at all. Not sure how to explain the issues you are seeing.
    – acejavelin
    Commented Feb 27, 2017 at 4:49
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    The USB 3 spec is fully backward compatible with USB 2, and USB 2 devices should always work on USB 3 ports. However, I do hear occasional reports of specific hardware not playing nice.
    – fixer1234
    Commented Feb 27, 2017 at 4:50
  • Thanks for your comments acejavelin & fixer1234. Looks like I need to do further troubleshooting at my end as to why those devices are not working in USB3 ports.
    – patkim
    Commented Feb 27, 2017 at 7:16

2 Answers 2

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@AliChen seems to be on the right path, actually this is a good line of thinking I hadn't considered. I never checked the motherboard specs when I posted my comment. This board uses a NEC (now Renesas) D720200F1 USB chipset for it's USB 3.0 ports, which seems to need a firmware update for full compatibility with published USB 3.0 standards, more information is available here. There is also information on TechPowerUp forums on more updated firmware information for this chipset as well.

Renesas does not offer the firmware update directly from what I can see, so it might take a little trial and error. Gigabyte seems to have no official update on their site that I could find either and this firmware is not part of your BIOS.

Remember that anytime you mess with firmware, especially in older hardware like this, there is a potential of something to fail or go wrong. Just giving you fair warning, do with this information what you will.

However the other answer of replacing the motherboard should be considered given the age and the relatively cheap availability of AM3/AM3+ motherboards that are comparable or superior to your existing board.

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The Gigabyte 880GM-USB-3 motherboard is based on AMD 700-series chipset, which is nearly a 10 years-old design. The board likely uses a third-party USB 3.0 chip for USB 3 functionality. Ten years ago there were no functional USB 3.0 at all, and there were various odd ideas on how to blend USB 2.0 ports numbering into USB 3.0 port numbers, so massive confusion in architecture of drivers existed. My advice would be to get a modern board and do not waste your time debugging earlier prototypes of USB 3.0.

Actually, asking generically if USB2 devices are compatible with USB3 or not doesn't make much sense, because every USB3 port is the old USB 2.0 port with extra USB3 Tx and Rx pair of wires on top, literally. They are run by nearly totally separate controllers. The USB 3-style connect detection is supposed to happen first, which is based on presence of terminated links. The host transmitter is supposed to send special pulses to detect the line load. If load (USB3 device) is not detected, USB3 should shut off completely, and listen to pull-ups on old USB2 wires. Then follow the standard USB2 procedures. This sounds as fail-proof, but apparently older USB3 designs had implemented the process in somehow deficient way. A USB2 device has no idea about any extra wires or any connect detect procedures, and fires the old-style USB2 connect signaling right away, or with some delay, depending on device. But the old Renesas/NEC host controller apparently doesn't like the premature connect on USB2 lines, and apparently fails to properly report the connect event to host system registers.

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  • Thanks Ali Chen & @acejavelin. While it started with a very basic question, this discussion lead me to further investigation. May be I should have mentioned that I have Revision 3.1 of the board. The NEC chip is being used by Gigabyte in Revision 1.1 of this board whereas Rev 3.1 uses Etron EJ168 USB3 controller. gigabyte.us/Motherboard/GA-880GM-USB3-rev-31#sp The specs of Etron EJ168 indicate compliance to USB 3 V1.0 and backward compatibility with USB 2.0, 1.1 & 1. etron.com/en/products/u3hc_detial.php?Product_ID=1
    – patkim
    Commented Mar 1, 2017 at 4:05
  • Continued... For experimental purposes I installed Windows 8.1 64 on spare HDD in same PC and found my same USB WiFi adapter working just fine in USB3 port on Windows 8.1 on the same board. That makes me wonder if drivers for Windows 7 are the culprits somehow.
    – patkim
    Commented Mar 1, 2017 at 4:05
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    @pat2015, just to be clear: USB host is maybe 10% hardware, and 90% software. The USB hardware is essentially a linked-list processor working as bus-master. Most of USB basic functions (port conditions, link status management, reset/sequencing) is also software-based. Whichever structures are placed in main memory by host driver and a lot of other things, all this will define correctness of USB functionality. So both parts usually have bugs, and hundreds of workarounds are there. So there should be no surprise that there are some snafus in older hardware/software, and in new one as well.
    – Ale..chenski
    Commented Mar 1, 2017 at 4:56

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