New Build issue

Ponster

I've just put together a new build and I think I've made a mistake.

I built it last night and realized that the gfx card (Asus HD 7970) has 2 8-pin PCI-E sockets but my PSU only has 1 8-pin PCI power connector and 1 6-pin PCI power connector.

Some forums have suggested that I don't need both 8-pin connectors unless I want to overclock or if the card is under heavy load but I can't get the system to 'see' the card in Windows with just the 8-pin and 6-pin connected.

When I plug in the available PCI power connectors I notice 2 LEDs on the gfx card like in this image. I have a green and a red LED. The site I took that image from says

"When a six-pin connection is fitted with proper power a green LED light shines to indicate ideal operating conditions, or the LED shines red when insufficient power is supplied or not connected."

On boot I see 1 green LED and 1 red. The fans spin but I see nothing in Windows. When I plug the DVI from the internal mb to the Asus gfx card the monitor doesn't light up.

Have I really made a mistake in getting a PSU which has enough power to for everything but won't power the GFX 'cos I don't have 2 8-pin connectors?

maki

You can plug a 6-pin connector into the 8-pin slot, but be careful you put in in correctly and don't force it in the wrong way. Be aware that the 6-pin connector will not supply as much power as the 8-pin one (75W vs 150W if I recall). It's worth a try if you only need a little more juice to get it running.

Otherwise, and assuming that you have 2 free molex connectors, get a molex to PCI-E adapter. Something like this, although you might be able to find a cheaper one: http://www.ebay.ie/itm/2-x-Molex-4pin-Male-to-8-pin-PCI-Express-15cm-Y-power-cable-for-PCI-Express-card-/150954190855?pt=UK_Computing_CablesConnectors_RL&hash=item2325922807

roast

Maki's right. 6-pin PCIe provides 75w of power, 8 pin provides 150w of power, and the card itself can draw ~75w.
The card itself peaks at 300w.
It's possible that the PSU simply can't provide enough juice for the card and the rest of the system, but I'd definitely recommend to get a molex to PCI-E 8 pin adaptor to test with.
That PSU provides 48A across the +12v rails, it's also possible the card needs more - I can't find the card's requirement in the specs.

Ponster

maki wrote: »

It's worth a try if you only need a little more juice to get it running.

Yeah I tried it but that's when I still get a red LED where it's plugged in.
Thanks for the cable suggestion. Amazon Prime should have it to me tomorrow!

roast wrote: »

Maki's right. 6-pin PCIe provides 75w of power, 8 pin provides 150w of power, and the card itself can draw ~75w.
The card itself peaks at 300w.

I'd hope that 620w should be good enough for the system (my calculations came to about 520w) and I *thought* that I had worked out that the PSU matched the cards power requirements.

I'll get that cable and we'll see what happens next !

Ponster

So I got the extra connector and plugged it into the gfx card. Got 2 green leds and hit the power button and....nothing.

It's like I have a short somewhere. When I switch on the fans all begin to spin for a split second and then just stop. All leds flash and then go out. No beeps.
Same problem no matter which PCIe slot I use.

I'll take it apart this weekend and try with the MB out of the case but I doubt that it's a short seeing as it works fine with the card out.