GA-MA785GM-US2H USB KB issue

GBs have 'issues' with certain USB devices - see:
http://www.tomshardware.com/forum/261902-30-gigabyte-ta...
and:
http://www.tomshardware.com/forum/260350-30-gigabyte-ep...
for examples... That said, yours is the very first time I have heard of a keyboard not working - and I think if an MS keyboard was 'generically' unable to work, there would have been complaints before; I think it's likely that the keyboard itself may be somehow defunct - and that doesn't mean it's not working - it may well work OK on a different (non-GB) system - your board just 'doesn't like it'! The only thing to try to alleviate it is to disable "Legacy USB storage detect"; if that doesn't work - time for a new (or at least, different) keyboard...  

I think the next thing to try is booting with the kb plugged in to the ps/2 port using one of those usb/ps2 adapters... will have to dig around and see if i can find one.

Thanks,

To be honest I didn't reread the refered to forum reports listed above. However I use a MS usb wireless keyboard quite old no problems. The best info I've seen suggested pluging into the usb ports next to or closest to the ps2 ports. That was reported to work. Also initialy dont plug any other unneccessary usb devices in until you're past this. I have the legacy support enabled on my Gigabyte 790x. good luck

Plugging into one USB port or another should not make any difference. They are all the same electronically. Unless one is defective.
You might want to borrow a different USB keyboard and see how it works. If the same problem, it's in the motherboard somehow. But try more than 1 port. IF the 2nd keyboard works, then it's your KB.

The 'closest to' business is like all web 'old wive's tales' - based on a cognitive misconception. Human beings are, at their basis, pattern recognizing and pattern matching automatons - it's what we do! But, people have a nearly impossible time understanding randomness, or statistical inference - it violates our 'pattern integrity', so we assign meaning to meaningless events... The source of superstition, and probably religion, too - "the Shaman prayed to the Great Lord Mota, and such happened!" People also have a vague (if any) grasp of what's going on at the hardware level - in fact, most recent graduates of our lovely educational system cannot tell you why, when you unscrew the living room lightbulb, and turn on the switch, the electricity doesn't run out on the living room floor! Somebody, somewhere, sometime, had a bad connector, or a bad jack, and when he plugged it in 'next to the PS2' (which makes no sense or difference physically - they're all just hardware 'hung off' the southbridge) it worked! ...And, yet another legend was born... He posted it somewhere, and some other dipstick read it, and it made some kind of sense to him, so he posted it again - and the rest is history... That's one of the resons I spend so much time here, trying to make issues that are, at their roots, hardware realities, clearer and easier to understand for the 'lay' user...

Well I gave up, found a perfect condition Microsoft Ergonomic Keyboard with ps/2 plug at a local thrift store ($2.99) and now have complete access to Bios on bootup.

I have no idea why the USB keyboard would not work.

I have the GA-MA785GMT-UD2H and I have the same problem with my USB keyboard during POST. If I hit the PAUSE button at the right time and then unpause it would sometimes work but the real solution was to install USB brackets for the extra USB headers and move my keyboard/mouse to one of them. Now it works fine.

The ports next to the PS2 port were the ones I initially used. I don't recall if I had success with any of the other 4 ports.

If any USB port (other than added ones on, say, a PCI card...) works different than any other, you have a bad chip 'channel', or a defective, or somehow 'marginal' connector - they're all the same: same hardware, same drivers, same bus connection!

Once I get past POST and into windows (using the far left USB ports), the keyboard and mouse work as usual, so it's not a connector issue. I have not had a single problem since I connected them to the USB bracket.