New system, either mobo or psu issues


I recently bought the following components for a new setup:
- Gigabyte GA-990FXA-UD3 motherboard
- FX4100 cpu
- Win 7 64 bit
- PSU: Cooler Master 500w
- Video: HD6870
- 8 gb ram (2 x 4 gb)

I called Gigabyte support and was offered some poor advice.

Computer will not post. Video is there (Black screen) but wont post. Is there anything as far as component connection that might prevent it from posting? i.e incorrect ram insertion, no keyboard etc.??

I dont have a traditional keyboard, just a USB one. When I connect it to USB the LED on the keyboard do not light up, so I don't think it's working properly.

Something about the PSU or/and the motherboard alerted me: the 8 pin ATX 12v female pins on the motherboard. Do all 8 pins need to have power running to them?

When I turn the system on with all 8 pins connected (2 2x2 plugs from the PSU) the system wont turn on at all. If I leave the 8 pin ATX 12 v empty (no power) the system turns on, all fans start spinning, but it won't post like I said before.

Any advice? Gigabyte support wasn't great. The guy suggested I buy another power supply first and try it out. But what if that doesn't help? I'm stuck with a bad mobo and 2 good PSUs?

BIOS note: support said my board is rev 1.1 and has AMD3+ BIOS on it.

Any advice? Thanks!
5 answers Last reply
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  1. sorry, but there's no definitive solution for a system not post.
    It may be bad power supply, or defect motherboard, or incorrect ram insertion (like you said above). You just have to ask some friend for a psu loan then, or bring it to a shop to test.
  2. 1. Computer will not post. Video is there (Black screen) but wont post. Is there anything as far as component connection that might prevent it from posting? i.e incorrect ram insertion, no keyboard etc.??
    You have three possibilities: pass POST (single short beep), fail POST (any other beeps), and no POST (silence). No POST could be hardware failure, improper installation, or especially in the case of AMD a CPU incompatibility that might be cured by a BIOS update.

    2. I dont have a traditional keyboard, just a USB one.
    You do not need a keyboard to POST. Keyboard LED's not working indicates a problem with the keyboard or, more likely, the PSU.

    3. Something about the PSU or/and the motherboard alerted me: ...
    If the CPU TDP is 120 watts or less, you can get by with a 4 pin CPU cable.

    4. When I turn the system on with all 8 pins connected ...
    System will not boot without the CPU power cable plugged into the motherboard. Without it, the results do not matter.

    With your component list, I would suspect the PSU first.

    Work systematically through our standard checklist and troubleshooting thread:
    I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

    If not, continue.
    The following is an expansion of my troubleshooting tips in the breadboarding link in the "Cannot boot" thread.

    I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

    Breadboard - that will help isolate any kind of case problem you might have.

    Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

    Make sure you plug the CPU power cable in. The system will not boot without it.

    I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

    You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

    If no beeps:

    Check for line power at the PSU input. Extension cords, power strips, and power cords do fail.

    If you have power and no beeps, suspect components in likely order are PSU, motherboard, and CPU.

    Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

    At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

    The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

    You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

    A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

    This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

    If the system beeps:
    If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

    Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

    Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
    At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

    Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
  3. I think you need to try to push hard on all the things to make sure they are firmly in their slots.

    It could be a few different things, but I am guessing one of them isn't seated correctly. RAM and power cables are two of the major things I am thinking about.

    - Edit - I just wanted to say that the people you talked to have a point. Cooler Master is a bad PSU brand. If it is the extreme power plus CM 500w that you have, it fails when you try to get 80% juice out of it. That means its really a 400w or less. You may not even be able to get more than 60% = 300w out of it. We tell people to get Antec, Corsair, Seasonic, or other Seasonic brands like XFX PSUs because they do what they say they are going to do unlike the dozens of other brands that don't. We can't rule out the PSU being a problem in the system as long as it is a tier 2 branded PSU.

    At least if you get a good one, you can be confident that the PSU isn't the problem and that the PSU isn't going to destroy your motherboard/video card because of dirty power delivery and insufficient power delivery and things like that.

    Even if it doesn't fix this problem, you will be better off with, say, a Corsair 520w for the long term than with a CM 500w.
  4. Thank you guys, appreciate it. I'm getting a replacement mobo already on the way, and I exchanged the original PSU with a Corsair 750w Enthusiast series.
  5. I have a gigabyte ga-990fxa-ud3 mainboard, everything was fine till last night I shutdown it. hence this I got no video, no keyboard liight and no usb pover(usb mouse light went dead). 12v fans working fine but there is no activity other than this. any suggestin?
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