Anyone help with strange boot?

CSlater · 21 Nov 2011 at 12:37

Hi. I've been having issues with my desktop PC booting up for around 3 months now which has me puzzled.

Simply, my desktop won't boot, even into bios unless I perform a little trick.

Ok, if I press down the power button on my case the PC tries to boot (I hear PSU, CPU and hard disks whir up) but get no signal on my monitor and it shuts down after a period of around 10-15 seconds. After another 3-5 seconds it will try to boot again and then shut back down permanently or try and boot itself a 3rd time.

Now onto the trick: To boot up I have to press the power button and wait for it to try and boot and shut itself down. Then I switch off the power at the PSU and wait..... Once I hear the fans whirr in it's attempt to boot up again I quickly switch on the PSU and if I time it right it will boot up normally. Once it's up and running I have no issues at all and have left it running for weeks without any crashes, bsods or overheating issues. Restarting from within Windows or the bios is no problem either. It's just once I shut down I have to perform this trick to get it going again.

My specs are:

Motherboard: Asus P7P55D
CPU: Intel i5 750 2.67ghz
RAM: G.Skill RipJaw F3-12800CL8D-4GBRM (2x2gb)
GPU: GeForce GTX260
PSU: BeQuiet Dark Power Pro P7 850w
HDD: 2 X Samsung HD103SJ 1TB
SSD: Crucial M4-CT128M4SSD2 128GB
Windows 7 Home Premium

I have checked to make sure all jumpers and pins are in the right place, tried resitting the CPU and swapping the sticks of RAM around in different slots. All power connectors are tight and no bent pins anywhere and there's no pesky screws between motherboard and case shorting something out either.

I've tried clearing the cmos and pulling out the battery for 5 mins. I've updated the bios, chipset etc but nothing has worked.

Now, on my motherboard I have leds that light up as the bios (I assume) does it's checks. If I perform my trick the first to flash is the CPU led, then the DRAM led, then the VGA led and finally the Boot Device led before it boots into Windows. When it won't boot the CPU led lights up and stays on (until it shuts itself down).

That's about all the information I have right now and it has me stumped. Any ideas would be appreciated.

kristmace · 21 Nov 2011 at 12:52

Hmm, tricky one... I'm really not sure.

Have you tried
1) booting with only one stick of RAM.
2) a different PSU
3) a different mobo

Other than that, this has me stumped too.

danswan · 21 Nov 2011 at 12:59

I've had similar issues in the past, always comes down to some hardware confilct.

As above, but try different GFX as well.

Gregster · 21 Nov 2011 at 14:23

I would deffo try a different psu first off.

It is a strange one though and if not psu then it would lead me to think it is mobo related.

Good luck bud.

hominid · 21 Nov 2011 at 15:29

I had a problem similar to this with my old Motherboard(P5Q) and a dark power pro 750, it wouldn't boot sometimes with all the fans spinning to 100%. The only way to get it to boot was to turn it on, so all fans 100% no output to screen, and then turn off the power switch then quickly turn it back on. Then it would boot 80% of the time else I would do it again, once booted the machine was 100% stable.

In the end I had to change the power supply to an antec 650W and all was fine for a year or more.

//edit, I'm now using my dark power pro 750 with my new build and it's been fine for months, so it was some weird incompatability between the motherboard and power supply - very odd.

CSlater · 21 Nov 2011 at 18:15

Thanks for the replies.

@all:

I've swapped the ram and tried one at a time (in various slots) but it makes no difference. Since it's hanging on the CPU post state LED then I can't see it being RAM or GPU related. As most of you are thinking, it's either the motherboard or psu.

Unfortunately I don't have a spare motherboard or PSU to test. If I had to put money on it I'd say it was the PSU. Does it sound like I have grounds for an RMA ofthe PSU?

Gregster · 21 Nov 2011 at 19:39

You do but the problem being if no defect is found then you will have to pay the fee. What I would be inclined to do is buy 1 from pc world or similar to try it and if that works then sweet but if not take it back and get your money back. Maybe a little naughty but...

CSlater · 22 Nov 2011 at 12:35

After a bit more research I found a post on the Asus forums regarding my mobo and similar booting issues to mine. Here's one reply:

----------------------------
"What kind of PSU (power supply unit) you have? There is a known problem with some Asus motherboards and high power PSUs with low starting current i.e. load when booting. Could you try with a different PSU?

Symptoms are as you described, board tries to power up, fans starts and then shut down because starting takes too long time. it has been tested (I don't remember where, Anandtech.com perhaps) that some Asus motherboards require at least 1A comparable load during start up."
-----------------------------

Anyone know anything about this? Could it be that my board is one that needs a little more power at startup and me switching down the PSU switch at the right time is somehow giving a little more juice at the right time?