Question for hardware gurus

[Axxon]

I am having a difficult time adding a graphics card to a new computer I bought. I bought a 9800 gtx+ and a new power supply at the recommendation of the sales drone and it turns out he sold me a slightly underpowered psu which I need to replace but for the time being I'm trying to get it to work.

It only has one pci-express adaptor and the card needs two. It'll run on one but the card scales back it's performance. I went out and bought a 2 molex to pci-express adaptor and this thing will only work with a molex in the left slot. I can take the same molex, put it in the right slot, pc doesn't boot. Put it in the left one, everything runs ( and the card runs at full capacity ). It doesn't run with two molex plugged in. Anything in the right molex spot and the pc won't boot.

I've tried every molex on the PSU. Put something in the right plug and the machine doesn't work. It only works if you only have one molex in the left slot.

I bought a second adaptor and it's the same thing so it apparently isn't a bad adaptor. Any ideas what gives? This is very odd to me.

[dacman]

On the card, one of the PCI-E power plug-ins is a "primary" and the second is like a "booster." If you don't plug in power to the "primary," the card won't work. If you plug in both, but get nothing, your PSU may not have enough power.

The only way it will work (fully) with your setup is if you have a molex coming out of your power supply tied to the 12V rail, which you may not have. (Most of the old-style molex connectors on a PSU are on a 5V rail). Usually if one of the molex connectors is on the 12V rail, it will be stamped or labeled somehow. My power supply has one with "12V" stamped on the connector itself. If your power supply only has 2 12V rails, you probably do not have one.

[Axxon]

Originally Posted by dacman

On the card, one of the PCI-E power plug-ins is a "primary" and the second is like a "booster." If you don't plug in power to the "primary," the card won't work. If you plug in both, but get nothing, your PSU may not have enough power.

The only way it will work (fully) with your setup is if you have a molex coming out of your power supply tied to the 12V rail, which you may not have. (Most of the old-style molex connectors on a PSU are on a 5V rail). Usually if one of the molex connectors is on the 12V rail, it will be stamped or labeled somehow. My power supply has one with "12V" stamped on the connector itself. If your power supply only has 2 12V rails, you probably do not have one.

No, it's not which plug I use on the card. I get the same behavior on both. The molex itself plugged in to the right side of the adaptor means the whole pc doesn't boot. On the left side, everything works. Both plugged into the same adaptor, pc doesn't boot.

All of this is both with and without the dedicated pci-e is plugged in as well, again, in either slot.

I don't doubt what you're saying though and this weekend I'm going to return the PSU and get a new one but I just don't get what's happening here.

[Axxon]

dola to add.

Not using the adaptor and only the dedicated pci-express, card runs at reduced settings, adaptor plugged in as well with molex in left plug, card runs at at full settings.

[dacman]

You might have a pass-through adapter instead of a 2-to-1. Otherwise, I'm at a loss. If it works fully the way you described, you should be good.

[Axxon]

Originally Posted by dacman

You might have a pass-through adapter instead of a 2-to-1. Otherwise, I'm at a loss. If it works fully the way you described, you should be good.

Why would a passthrough have two molex connectors then? What would be the point?

I'm at a loss too.