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I've just bought a Radeon HD6870 but when I install it my machine doesn't even POST. I had to get a PCI-E power connector adaptor (2xHDD sockets to PCI-E 6-pin plug) as my 500W power supply only had one PCI-E 6-pin plug and the card needs 2. I've also upgraded the BIOS to the latest release.

All the fans and Drives spin up, but the USB mouse doesn't light up.

Should I get the graphics card checked, or should I just pony up for a new (bigger and better) power supply? (or is there something else I should try)

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migrated from serverfault.com Mar 16 '12 at 18:17

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Thanks to all the replies. It turned out that I did have a "dodgy" (probably just older) power supply so the new (750W) PSU solved my problem just fine –  NeonGraal Apr 16 '13 at 4:34

3 Answers 3

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Get a new power supply. After you work with it using Sidran32s excellent advice for checking.

The reasons I am going with that advice, it sounds like your PSU is not "up to date" and as power supplies age, the capacitors age. If it was a cheap psu to begin with , it could be weak, and dirty. The new card might put you in a good position of upgrading the PSU to a better quality , and newer version, even one that is more efficient , more quiet and better quality.

If you need an excuse to update the PSU , and the psu is aged or junkey. If the psu does not have the multiple GPU wires and High amp 12V rails, they put on the new ones. it might be a good time to do that when putting in an expencive GPU, and trying to make sure everything works well.

Then you still have the First problem :-) which should be easier to deal with when you have one less item in there to worry/wonder about.

Side notes: - - - - - - - - - - - - -

Some of the Motherboard connections are NOT compatable with PCI-E connections because of odd things they do different with the wiring, like extra ground on 8pin PCI-e. So checking your polarity by at least looking at the color coding of the wires , and checking manuels and any polarity + - signs on the cards (where the power connects).

If you use a Modular PSU the wires are NOT always the same between manufactures.
These 2 things have had some serious consequences for some people , who learned while they burned. When making the changes and adaptions, take extra time to check things, before the plug goes into the wall.

Remember a PSU is not "off" when the computer is in the off state, you must turn off the power supply switch, or remove the plug from the wall (or both).

I have had situations where a video card (and the psu) were fine and the card just would not Init right away. It would just not work, and the computer would not boot, and persistance with it paid off. When it finnaly booted it took 5 minutes for some strange reason. Other users have reported that happening, I still do not know what to attribute it to.

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(Assuming you don't have anything else significant in the computer, a 500W PSU should be sufficient in your specific case. Especially when not under heavy load.)

When presented with your situation, the first thing I would try is to remove the graphics card and replace it with another one that you know works, or use integrated graphics (if available). If the PC boots fine, then there was something wrong with the graphics card. Put it back in and try again, making sure that it's seated properly and everything is hooked up as it should be. If it still won't work, then it may be a defective card (not unheard of) and you may need to RMA it.

If swapping the card out does not fix the booting issue, then the problem must lie elsewhere. Some motherboards give error codes using flashing LED patterns on the front panel of the computer or on the motherboard itself. Check to see if it's indicating anything. This should give you some guidance.

If not, then I'd start with the basics. Begin by cleaning out any extraneous dust and verifying that all cables and power connectors are properly hooked up where they should be, including the keyboard (which sometimes can fail a POST). After that, verify that everything is seated properly (any other add-in cards and RAM, first). Then I'd make sure that the PSU is working. Try it in a different computer, or try a different PSU, if possible. Then, start making sure that the processor is seated properly, and that you didn't jolt or damage it somehow. If it's still not working, I'd suspect the motherboard may be at fault.

Take it slow and test each component individual as you replace/reseat/check it. That way you will immediately know what is at fault as you rule things out.

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HD 6870 1GB power consumption 247W default and system not more than 250 W, thus - good 500W PSU will work. Sidran32 and Psycogeek give you good advice, I'll try to check +12V lines also: 12V maybe not 12 or unstable, current may be (for the old PSU) below the promised

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