9800GX2 power plug and power supply

[Toastman]

Okay, I'm getting a little confused on the phsical power connection requirements for the 9800GX2 cards. It would appear different cards have implemented different combinations of power connections, but 1x 8-pin and 1x 6-pin appears to be pretty common (some have 2x 6-pin, which leads me to believe two connectors are indeed necessary). Can anyone clarify if it actually needs both connected to properly power the card? The reason I ask is because power supplies with both 8-pin and 6-pin PCI-e power connectors are actually pretty rare. Even the highest end power supplies generally have either only 8-pin connectors or 6-pin connections, but few have both. Am I missing something here, or has there been a disconnect between the video card manufacturers and the power-supply manufacters?

Thx for any feedback!

 

[Toastman]

*bump*

High-end video cards and power supplies aren't cheap, and I don't wanna end up with a set that isn't compatible.

 

[nitromullet]

All GX2s require a 6 and an 8 pin power connector. That being said, my psu actually only has two 6-pin connectors and I'm using this adapter to make one of them an 8-pin:

http://www.performance-pcs.com...=186&products_id=21721

If you're looking for a power supply that you can be sure is compatible with a GX2, check this page out:

http://www.slizone.com/object/slizone_build_psu.html

...although that is actually for dual GX2s...

 

[imported_wired247]

When buying the 9800 GX2, I decided to abide by BFG's recommendations:

minimum 580W psu, check
minimum 40A on 12V, check
minimum 2 PCIe 6 pin connectors, check

and that worked out just fine for me.

if you meet these requirements and your PSU is good quality you should have no problems using a 6pin->8pin pcie adapter. But yes, you need to connect an 8pin and a 6pin to the card. You cannot stick the 6pin in the 8pin slot without an adapter.


XFX and eVGA for example do not "allow" this configuration on nVidia's recommendation. Tech support at XFX told me over the phone that it might "damage" the card. But, that has turned out to be a bunch of FUD that didn't apply to me.

I believe the reason they spread this FUD is because they don't want idiots with 300W psu's blowing PSU's and video cards left and right and then trying to get RMA service on their cards.

 

[imported_Shaq]

I bought the Cooler Master Real Power Pro for just that reason. It has 2 true 8 pin (not 6+2) and 2 6 pin connectors. It is only $100 AR at Newegg for 750 watts continuous. The adapter I'm sure works fine but since I was buying a new power supply anyway I figured it was better to get one that didn't need adapters. And I can get an adapter if I need more 6 pin connectors down the road. I imagine it is better to go from 8 to 6 pin than 6 to 8 pin as the 8 pin supplies more power than the 6 pin connector needs.

 

[nitromullet]

Originally posted by: Shaq
I bought the Cooler Master Real Power Pro for just that reason. It has 2 true 8 pin (not 6+2) and 2 6 pin connectors. It is only $100 AR at Newegg for 750 watts continuous. The adapter I'm sure works fine but since I was buying a new power supply anyway I figured it was better to get one that didn't need adapters. And I can get an adapter if I need more 6 pin connectors down the road. I imagine it is better to go from 8 to 6 pin than 6 to 8 pin as the 8 pin supplies more power than the 6 pin connector needs.

A better would idea would be to get a solid single 12V rail unit. That way it doesn't really matter if you have to use an adapter or not, as you have the total rated 12V output available to you in whatever cable configuration you choose.

The CoolerMaster has three 19A 12V rails meaning that each rail has a theoretical max output of 228W. Given the fact that combined a 6-pin and 8-pin PCIe connector should be able to provide up to 225W of power, you could potentially be pushing one of those rails really hard if the connectors used are all on one of the three of the rails.

specs from the box:

http://www.hi-techreviews.com/..._Pro_750W/IMG_2992.JPG

 

[imported_Shaq]

It actually has 4 rails @ 19A. There are misprints on the box and on the website. But the manual and power supply sticker show 4 rails. Yeah I wouldn't run more than 200 watts per rail to be safe. All the single rail supplies that I saw around $100 or less used 6+2 connectors which are more versatile but also a pain to deal with sometimes. ie. especially a GX2 with a thin tab slot. The 8 pin on this PS slipped right in the slot. And 750 watts continuous and 900 watts maximum was the most output at that price point. But it changes week to week depending on sales. I will likely not ever have 2 vid cards anyway. Though if I do this PS should run 4 6 pin connectors flawlessly just not 2 8 pin and 2 6 pin.

Believe me when multirail PSU's started coming out a few years ago I knew a single rail would be the best for most situations and would allow you to extract the most power. It has taken the industry 5 years to realize it though.

 

[nitromullet]

http://www.hi-techreviews.com/..._Pro_750W/IMG_2997.JPG

Looks like they have a few mis-prints... 12*19*4 != 648

 

[imported_Shaq]

Originally posted by: nitromullet
http://www.hi-techreviews.com/..._Pro_750W/IMG_2997.JPG

Looks like they have a few mis-prints... 12*19*4 != 648

So I actually have 912 watts on the 12 volt rails!!!! LOL Just kidding. It is actually 648/12= 54A combined peak and about ~48A-49A continuous. The Corsair 550watt is 41A peak, 620watt is 50A, 750 watt is 60A and so is the PCP&C 750 watt. It looks like I'm missing 6A somewhere!! I guess it is not quite as good as those 750 watt units. I actually have a 670 watt continuous if not less.