I recently upgraded my main computer to a new shiny Intel Z68-based motherboard with a 2nd generation Core i7. A really nice piece of hardware, I'd say.
But while I was setting it up I had some very odd problem. When I plugged everything in and wanted to boot it, it just didn't want to boot any devices (but the EFI BIOS loaded without problems), it reset instead.
At first I thought I had a power problem, so I went out and bought a bigger PSU. But it still reset instead of booting. Then I called a friend and he thought the SATA controller might be busted. So he suggested unplugging everything and trying one part at the time.
After doing a lot of cross-testing I figured out that it was the USB cable to my APC Smart-UPS 1000 that stopped the boot from processing. So obviously either my UPS or motherboard firmware is incompatible with each other. Luckily I was not dependent on having the UPS USB cable connected, so I just disconnected it to avoid the problem. With that component disconnected everything worked as expected.
Moral of the story: Test with one component at the time if you're experiencing difficulties.
Good job narrowing down the problem and finding the device that is mucking up your reboot - however, calling that 'solved' is a bit of a stretch, isn’t it? I’d call it a workaround at best.
I have observed similar behaviour with an APC SmartUPS 1500 to an USB 1.1/2.0 port on an ASUS E35M1-M PRO motherboard (fw 1502). Fiddling with the legacy and EHCI handoff settings so far has not yielded any improvements.
The only thing that appears to work is connecting the UPS to one of the two available USB 3.0 ports – the motherboard POSTs and boots just fine. Unfortunately though my OS has problems with that approach (USB 3.0 related bug in Ubuntu 11.10 kernel).
Comment from: Member
@Mosez: You're correct that it is more of a workaround than a solution. I was planning on reporting the issue to ASUS, hoping for a firmware update, but never got around to it.
Have you reported the issue to either ASUS or APC?