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Crossfire with 2 HD4870s

MouthBoy

MouthBoy

MouthBoy

Soldato
Joined
6 Apr 2010
Posts
2,919
Location
Cambridgeshire
Hey dudes

Quite confused right now. I am looking to crossfire a second HD4870 with my current but there might be a few issues.

First, my HD4870 takes 2 6pins to power it, but this comes off 1 6pin from my PSU. I thought to myself, I must have a second cable then for a second GFX but I cant find one anywhere in my house. I have looked online too and still cant find one. I might be being blind but really cant find one. Will I need to buy one or will one come in the box for the second as I am buying new from OcUK?

Secondly, to my knowledge I got my crossfire bridge PCB with my motherboard and not my HD4870. Now, I have one of them, but for some reason the HD4870 wants 2 of them for the connection. Where would I find another to purchase, or again will this come in the box?

Lastly, I have lost my motherboard manual but I am sure it said that if I connected 2 GFXs to my motherboard that I would need to plug in an additional 4pin molex connection to the motherboard above the GFXs. Can anyone confirm this?

These are probably two really simple questions but they are just annoying me as I cant find the answers. Also this post might not read great as I am sitting here very confused right now. lol!

Thanks

Here are some images that might help. (Bad images due to iPhone).

2 C/F Bridge Connections
cf1.JPG


Power Connection
cf2.JPG


2 6pin connections
psu2.JPG
 
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For two 4870's you'll need 4 six pin connectors. These should come with the power supply assuming it's capable of supplying that much juice.

Crossfire connectors are supplied with the graphics card but you should only need 1 connector to crossfire two cards.
 
Surveyor said:
For two 4870's you'll need 4 six pin connectors. These should come with the power supply assuming it's capable of supplying that much juice.

Crossfire connectors are supplied with the graphics card but you should only need 1 connector to crossfire two cards.
Click to expand...

Well the PSU is compatible, and as the images show it has the connections for it but I just dont have the cable. Currently the one that powering the single card is a 6pin > 2 x 6pin, so I think I need another one of them.

Yea I too thought that I just needed one bridge, but the manual for the card states and has pictures saying I need two.
 
The connectors may be there but that doesn't always mean that you will have been provided with enough cables. Higher wattage PSUs tend to have more cables, lower ones tend to have less. My 600W unit has a lot less cables than my 700W one. My 600W unit has a 6+2 and a 6 pin PCI-E cable while my 700W has two sets for SLI/Crossfire use.

You could always use some of those Molex to PCI-E connectors.

2 x 4870 will drink quite a bit of power in use and also at idle. I would say you'd need a 700W supply, do you have this? If so you should have been given extra PCI-E leads really.
 
Yea it is a 700W power supply, but I am thinking of replacing it anyway. Its only an iCute 700W, it hasnt faulted yet but I dont seem to be able to find the cables from it now...
 
Looks like the icute modular 700w only has two 18A 12v rails so provide at maximum about 430w of 12v power. 4870s use about 170w from memory so two would need about 340w which doesn't leave a lot for the rest if your system. The icute should be marketed as a 450w supply and crossfire compatibilty is a lie, at least if you wish to use anything but low mid range cards.
 
A 6+2 connector is an 8 pin connector split so that it can be used as 6 pin or 8 pin.

In effect that power supply gives you two 6 pin connectors.

If you're crossfiring two 4870's you'll need a power supply with four 6 pin connectors.
 
Hum....ok then, can anyone point me in the direction of a PSU that will do this then? I seem to be looking for the wrong information.
 
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