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Old 09-16-2019, 06:43 AM   #1
dicky96
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Default Asrock Z87 Extreme 4 Not powering on

Hi guys
I picked this up at the local flea market together with a couple of other motherboards. I got one working so far (quite nice retro gaming board Asus P5PE-VM LGA775 with Core 2 support and AGP slot), and if I sell that it will more than cover the cost of all three so happy days.

So these others are mine to play with

The Asrock Z87 Extreme4 I don't have a compatible CPU to test it with, though I can get a LGA1150 Celeron or i3 cheap enough, so I will order one to test this and other 1150 motherboards in future, but basically right now, testing without a CPU, it will not power on.

I get 3.3V on the onboard power button which drops to 0V when I press the button so that looks fine. But the Power supply won't start.

If I ground the Power-On pin on the ATX connector it powers up and I have all supplies 3.3V, 5V, 12V inc the 8pin 12V to the CPU. I don't have any VCore but maybe that is normal with no CPU fitted?

But I would have expected the PSU to come on when I press the Power On button seeing as I have 5.5VSB and 3.3V present.

I already fitted a new CMOS battery the original one was flat.

Is there anything I can check here before I get a CPU?

Rich
PS the third board I got is a GA-EP45C-UD3R. It has a low resistance on the 12V supply to the CPU and trips off the ATX supply so I'm looking at that now. It will power up with the 8 pin 12V unplugged. That could be another thread if I can't find the problem with the VRMs
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Last edited by dicky96; 09-16-2019 at 06:48 AM.. Reason: add pics
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Old 09-16-2019, 03:37 PM   #2
cpt.charlie
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Default Re: Asrock Z87 Extreme 4 Not powering on

In order to generate Vcore you need to have a processor installed as the motherboard needs to read the VID form the CPU.
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Old 09-16-2019, 04:09 PM   #3
piernov
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Default Re: Asrock Z87 Extreme 4 Not powering on

Some boards will not power on without a CPU inside the socket. Not saying this is the case here, but I've already lost time trying to figure out a non-existant issue just because I assumed any board would turn on without CPU…

Try to grab schematics and/or boardview, it'll help in the troubleshooting process.
If not available, at least get a datasheet or pinout for the SIO.


For the Gigabyte board, replace all high-side MOSFETs and their drivers and it should be good to go. If CPU VCore has low resistance to ground without CPU, low-sides will have to be replaced too.
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Old 09-17-2019, 03:59 AM   #4
dicky96
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Default Re: Asrock Z87 Extreme 4 Not powering on

Thanks, I'll leave this one on the TO DO pile until I get a suitable CPU

I was wondering is it possible (or useful) to force Vcore on without a CPU by connecting some pull up resistors, or by grounding some of the VID pins on the controller chip, therefore presenting a valid 6 bit code?

Rich

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Old 09-17-2019, 05:06 AM   #5
dicky96
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Default Re: Asrock Z87 Extreme 4 Not powering on

I'll put the GA-EP45C-UD3R on it's own thread
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Old 09-17-2019, 07:37 AM   #6
piernov
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Default Re: Asrock Z87 Extreme 4 Not powering on

On older platforms you could do it since it was the old "VID" protocol with indeed just a 5-8 bits value to set on some pins of the VCore controller.
On newer platforms, it is the "SVID" protocol, Serial VID, that is used. It's an Intel proprietary protocol to have a serial communication (with a data and a clock line, plus an "alert" interrupt line) between the CPU and the VCore controller. It's not possible to know what happens there, much less control it (would need to find a leaked spec of the protocol, they are under NDA, or reverse engineer it and have the proper hardware).

However, some VCore controller can be configured to output a default voltage when nothing is received on SVID. They'll typically be configured to output 0V on a production board, but if you can find the datasheet of the IC you may be able to locate a pull-up or pull-down to replace to output a default value of 1.1V for example.
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