Dealing with 1 PCIE 6 pin on a 800W PSU

ImperialJoe · Jul 21, 2014

A few years back I bought the FSP800-80GLN with a huge discount. It has as much as 4 12v rails providing 20A each. The problem is that it only has 1 PCIE 6 pin connector.

I want to run an R9 290. How safe will it be running 2 more 6 pin via 4 molex cables, and then adapting both of them to pcie 8 pin plus the existing 6 pin?

The rest of the system is a 4790K overclocking build.

Thanks for answering!

Eduello · Jul 21, 2014

1 PCI-E connector on a 800W unit tells something about the quality of the unit, I would get a new PSU.

Karsten75 · Jul 21, 2014

Just yesterday I looked it all up.

Max watt per connector:

Molex: 132W (11 Amp))
6-pin: 75W (6.25 Amp)
8-pin: 150W (12.5 Amp)

Your rails claim to provide 20A (240W) per rail. Since you have 4 rails, that's already 960W which is way over your PSUs rated ability. I'd be very careful with those specifications.

I've seen connectors that conenct two molex into one 6/8 PIN.

Do you have a schematic on how the rails are allocated to the various connectors? That may also affect your decisions.

ImperialJoe · Jul 21, 2014

Eduello :

Still, FSP isn't some typical generic PSU manufacturer. I really don't have budget for anything else. I intended to run:
1 PCIE 6 pin + 2 molex 4 pin to PCIE 6 pin to 1 PCIE 8 pin to card
2 molex 4 pin to PCIE 6 pin to card.

Eduello · Jul 21, 2014

ImperialJoe :

That might work, but you need to figure out which rails you're using as Karsten75 stated above. You must use molex connectors that are on different rails than your CPU and your PCI-E 6-pin connector, otherwise you might end up overloading a single rail.

Karsten75 · Jul 21, 2014

ImperialJoe :

I'm with Eduello on this. In the PSU tiered list, FSP is all over the place from Tier 1 to Tier 5. and any unit with 4 rails and that claims to delive more per rail than it's total rating is a very suspect unit.

ImperialJoe · Jul 21, 2014

Karsten75 :

ImperialJoe :

I'm with Eduello on this. In the PSU tiered list, FSP is all over the place from Tier 1 to Tier 5. and any unit with 4 rails and that claims to delive more per rail than it's total rating is a very suspect unit.

I guess I'll have to increase my budget yet again. What is the best budget friendly PSU for an overclocking rig with a 4790K and a R9 290? And for an R9 290 CFX?

Eduello · Jul 21, 2014

This would be enough for a single R9 290: http://pcpartpicker.com/part/xfx-power-supply-p1650xxxb9
For 2 of them: http://pcpartpicker.com/part/evga-power-supply-120g21000xr

ImperialJoe · Jul 21, 2014

Eduello :

Neither is available in my country and is 1000W really needed? In Guru3D's review their system needed less than 650W in CFX, and I thought about something like the Seasonic M12II 850W to be on the safe side with overclocking. Also, it's tier 1 according to the PSU tier list. I thought it would be enough if I decide to add another R9 290.

Eduello · Jul 21, 2014

Yeah, Seasonic is a quality brand and 850W would be enough, but 1000W would give you more headroom for overclocking.

ImperialJoe · Jul 21, 2014

Eduello :

A proper 1000W PSU costs almost twice as much, I think I'll pass on the offer.
Which is better - Seasonic M12II 850W or Antec High Current Gamer 850W?

Eduello · Jul 21, 2014

Both of those units are high quality, get whichever is cheaper.

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