Member Avatar for DeC

Hello,

I recently bought a new video card and i have a serious problem with it. It is a brand new EVGA GeForce 7800 gs 256 agp oc editon. I connected it all right to an exclusive 4-pin molex plug straight from the psu and with nothing else on it. Problem is that I can’t get my pc to boot correctly, it often boots-up, operates for 5-10 seconds and then the system crashes with an immediate distortion of what the screen shows at the time and nothing else happening onwards, just a system crash. Sometimes it even crashes and freezes when calculating the memory at the beginning. When that occurs and I switch it off, the pc won’t boot-up at all for a period of 10-minutes or so and some times when I try to boot it up I get the whistling alert from the motherboard that corresponds to the video card not being powered at all, even If I have all the connections from the power supply correctly.

System setup is all ok and i checked around many forums with everyone suggesting that my psu is not powerful enough. However, evga customer support told me that it should be sufficient.

POWER SUPPLY

CHIEFTEC
GPS-550AB A (ACTIVE PFC)

Rated Power: 550w with +12V carrying 18A and 216W

After all this though, i found out that this power cable here:

was missing from my package, even if it was sealed with the safety tickets, both sides!!!!!!! THANKS A LOT EVGA ! ****!

Which one's that exactly? I have to get one today from a pc store, if i am lucky to spot one of those!

Is it the pic connector (6pin) which has 3x12v + 3xground? Is this what causes the problem? 'Cause i had the card connected directly to a 4-pin molex which goes up to the power supply. What's the difference between the two (if any) in regards to the power being sent to the card?

Thanks a lot,
D

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  • Latest Post Latest Post by caperjack

Dani AI

Generated

Both the 4-pin peripheral (Molex) and the 6‑pin auxiliary connector carry the same nominal +12 V, so the issue is not a different voltage but how that voltage is delivered. As noted, the 6‑pin format is designed to supply higher sustained current by using three +12 V conductors and three grounds to spread the load; a single Molex puts all of the GPU current through one 12 V feed and fewer ground paths, increasing the chance of cable heating, connector voltage drop, and PSU rail sag.

The reported behavior (system starts, runs a few seconds, then artifacts/freezes or fails POST) is characteristic of power delivery collapsing when the GPU initializes or ramps up clocks. Transient instability under load points to insufficient current capacity or poor distribution rather than a different nominal voltage.

Practical checklist and troubleshooting:

  • Confirm the card needs an auxiliary 6‑pin feed (card manual or visible socket).
  • Prefer a native 6‑pin PSU cable. If an adapter is used, use a quality two‑Molex -> 6‑pin adapter that sources power from two separate peripheral cables (not two connectors on the same daisy‑chained cable).
  • If possible, test the card with a known‑good PSU that has a native 6‑pin connector to isolate the problem.
  • Monitor the +12 V rail under load (hardware monitor or DMM) for sag; persistent droop indicates the PSU or wiring is at fault.
  • Replace the PSU if it cannot supply stable +12 V current under GPU load.

Caution: cheap single‑Molex hacks or overloaded Molex lines can melt connectors or damage components. The root cause is current delivery and wiring, not the nominal 12 V itself. Addressing the connector/wiring or using a properly rated PSU is the reliable fix.

Recommended Answers

All 4 Replies

Member Avatar for Belrog

There should not only be a voltage difference on the connectors, but also a rated current difference as well. This can result in some big differences in power delivery.

Member Avatar for caperjack

There should not only be a voltage difference on the connectors, but also a rated current difference as well. This can result in some big differences in power delivery.

Hello ,the posts you are responding to are over a year old ,this site need more helpers like you ,but you might want to try helping non answered post that are a little newer ,just a suggestion!

Member Avatar for Belrog

I know, I know. But next time someone searches, and find a thread that looks like something they can use at least there will be something to use.

I just hate getting a thread that looks exactly like what I need, and then there is nothing there except the problem.

Member Avatar for caperjack

I know, I know. But next time someone searches, and find a thread that looks like something they can use at least there will be something to use.

I just hate getting a thread that looks exactly like what I need, and then there is nothing there except the problem.

good point ,keep on a posting!

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