Crossfire on a x4 PCI Express Slot

crispykiller96

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Hi there i have just bought a R7 260X 2GB Graphics card to upgrade from my ageing GTX 460 768MB now i have a second slot but at 4x speed is it worth adding the same card in the future or will the x4 speeds throttle the graphics card also about performance how will it perform with x16 and x4 my motherboard is the Asus Evo R2 with the 8320 and 1050 watt 80+ PSU is it worth it thanks

Joe
 
Solution


The 4x slots on most motherboards are typically located towards the bottom. These slots are wired to the PCH/Southbridge rather than the CPU or Northbridge. If I recall correctly, NVidia does not allow SLI on PCH connected GPUs and will not certify a motherboard as SLI capable unless it has two 16x slots connected to either the CPU or Northbridge...

Eximo

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[strike]List the motherboard make and model.[/strike] Wow my vision must be going...

Not seeing what you are talking about. You should be able to do a full crossfire setup with that board. Though if you are looking to invest, you should just go for a single faster card like the R9-290 or R9-290X rather then a pair of mid-range cards.

Unless you meant the ASUS M5A97 , in which case you could do 16x/4x, but that makes the recommendation for a single faster card more appealing.
 


The 4x slots on most motherboards are typically located towards the bottom. These slots are wired to the PCH/Southbridge rather than the CPU or Northbridge. If I recall correctly, NVidia does not allow SLI on PCH connected GPUs and will not certify a motherboard as SLI capable unless it has two 16x slots connected to either the CPU or Northbridge. AMD is a bit more forgiving in this matter as I have seen Crossfire capable motherboards that have only one 16x slot connected to the CPU/Northbridge and a second 16x slot in 4x mode connected to the PCH/Southbridge.

If the motherboard box advertises Crossfire, it should work just fine.

EDIT: There may be a slight performance penalty due to the extra hops that the data needs to take. I doubt that this would be a severe problem with a midrange card though.

EDIT2: It looks like the AMD 970 chipset provides a 16x static link and a 4x static link, so both slots should be connected directly to the Northbridge on that motherboard. It also supports Crossfire. Have at it!
 
Solution
The x16 card will run at X4 to match the second card. With faster cards, that is an issue, but with slower cards, not so much so.

Regardless, whenever you need another graphics upgrade, it will be simpler to sell your current card and replace it with a single stronger card. You will avoid any dual card issues like tearing or stuttering.
 


No it won't. GPUs that are in a Crossfire configuration can operate on different link speeds without issue.
 

Thanks, I stand corrected.
But... if the two cards do not perform the same, will that not cause such issues as screen tearing?
 


Naw. Even the most highend cards show a negligible change in performance when the link speed is constricted. This effect is suppressed when Crossfire is used
 

crispykiller96

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Hi there thanks everyone the board was M5A97 EVo R2 i should have specified it a little better the box states Crossfire technology and windows 8.1 as you have mentioned both cards will run at x4 to match the 2nd slot which would be the 2nd card would the performance increase be worth it as mentioned running 2 cards in 4x should do well as there not high end cards but is it worth it and how much does the performance increase i understand 2 cards at 4x will beat a single x16 card but is it worth it as i quite like this card and i have no intention of upgrading it anytime soon so doubling its power would be nice :)