please help with Z87X-D3H and 4790k problem

[chugger]

Hi, hope someone can help with this one! Very exhausted with trying various options already, and it's coming down to either a bad CPU or motherboard.

Motherboard: Gigabyte Z87X-D3H (tried bios F8 and F9)
Onboard graphics (HDMI)
CPU: i7 4790k
RAM: Kingston 4GB (tried all of 4x 4GB sticks I intend to eventually use in this machine)
PSU: Corsair RM650
Cooler: Noctua NH-U9S

While it very occasionally boots up fine (usually a cold boot), basically the machine usually keeps rebooting before POST.

If I leave it on its reboot cycle, it will eventually go into POST after 50 or so attempts, and I can enter UEFI bios after it does not find a boot device (I haven't got one connected yet). The CPU is detected fine in the BIOS when I get into it.

I updated the bios on this board using a G1820 CPU (so that Haswell Refresh would be recognised), and the machine boots into POST and BIOS every time when I swap the i7 for the G1820.

I also swapped out a known working PSU (Be quiet L7 630w if I recall correctly) and the same behaviour occurs, so I'm pretty sure the PSU is fine.

So I guess I'm asking - is this likely to be:

- a faulty CPU?
- is this even possible if it works *sometimes*?

- or a faulty motherboard?

[autotech]

Bios F9 would be the best for that CPU. Have you tried a different connection to monitor like a VGA or DVI connection. Sometimes a HDMI isn't the best to use at first.

What kind of usb devices are connected. A ps2 keyboard would be best at this point.
Strip it to CPU, 1 stick of ram, DVI or VGA cable with only keyboard and mouse. Does it still act up?

[evil]

Hello

Could be this: http://forum.giga-byte.co.uk/index.php?topic=15454.0 , a comparable situation? The PSU, SSD, DIMM ain't the problem. Some how the MB or CPU. I have KB and mouse both on USB, but I plug in a PS2 too, and had the same result.

[chugger]

Thanks for the replies.

I haven't tried DVI or VGA but the same behaviour occurs if no HDMI is connected too.

Only using 1 USB keyboard but again - situation occurs with keyboard connected or disconnected.

This is already stripped to CPU, cooler, PSU 24+8 pin, 1 stick of RAM.

I've also tried a known working PSU (Bequiet L7 630W) with the same results.

I guess the only way I can find out for sure is to try this CPU in a known working motherboard.. gonna be hard for me to access one

[chugger]

FYI this was a faulty CPU - I got it RMA'd by Intel, all seems well now.