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Crossfire HD7870 x8 questions?

Last response: in Overclocking
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March 4, 2013 2:42:41 AM

At the moment i have one HD7870 installed on my AsRock Z77 Extereme 4 Mother board.
I was wondering if my performance will increase if i run Crossfire HD7870's because i can only run them at x8 instead of x16?
Here is the specs of my motherboard: http://www.asrock.com/mb/Intel/Z77%20Extreme4/?cat=Spec...
Thanks for any responses.

More about : crossfire hd7870 questions

a c 130 U Graphics card
a c 83 V Motherboard
a c 177 K Overclocking
March 4, 2013 2:54:33 AM

PCI Gen2 8x is more than enough for the fastest graphics cards out there, that secondary slot will be running at Gen3 8x, which is equivalent to Gen2 16x.
You have no issue with bandwidth when it comes to dual Crossfire/SLI on the Extreme4.
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March 4, 2013 4:00:51 AM

manofchalk said:
PCI Gen2 8x is more than enough for the fastest graphics cards out there, that secondary slot will be running at Gen3 8x, which is equivalent to Gen2 16x.
You have no issue with bandwidth when it comes to dual Crossfire/SLI on the Extreme4.

So in other words i will get around double the performance?
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a c 130 U Graphics card
a c 83 V Motherboard
a c 177 K Overclocking
March 4, 2013 4:08:20 AM

Nope.
If a freeway is 16 lanes wide, but you have to get 8 cars down it, do the cars go twice as fast?

The 16/8/4/1x refers to the number of physical "lanes" (wires from the slot to the CPU) the slot has. The Generation (2 and 3 are all you need to worry about) refer to how much bandwidth each lane has, with Gen3 being double Gen2.
Having more bandwidth wont result in an increase to performance, unless your upgrading from a situation where you were already limited.

Or if I take your question a different way, yes you will have a rough doubling (often its an ~80-90% increase, drivers and games aren't perfect) of performance since you are now running two GPU's.
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March 4, 2013 4:21:50 AM

In reality, x4 gen 2.0 is usually good enough to run a card without getting a huge kick down in performance. At least for gaming. No idea about openCL oriented tasks and the like, which I assume, would suffer a lot more.
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March 4, 2013 4:39:18 AM

manofchalk said:
Nope.
If a freeway is 16 lanes wide, but you have to get 8 cars down it, do the cars go twice as fast?

The 16/8/4/1x refers to the number of physical "lanes" (wires from the slot to the CPU) the slot has. The Generation (2 and 3 are all you need to worry about) refer to how much bandwidth each lane has, with Gen3 being double Gen2.
Having more bandwidth wont result in an increase to performance, unless your upgrading from a situation where you were already limited.

Or if I take your question a different way, yes you will have a rough doubling (often its an ~80-90% increase, drivers and games aren't perfect) of performance since you are now running two GPU's.

ok thanks for that info! and clearing up what the x8 or x16 means! And yes by performance i meant will i get a ~200% fps increase with CF on games that are compatible with it.
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March 4, 2013 4:39:29 AM

Best answer selected by trigg.
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