CrossFire R9 390X

[nano__]

Hi Guys , i plan to purchase another Graphic card R9 390x but the my motherboard (msi z170 a gaming m3 )running one 16x and other 16x @ 4x , is any different between running 16x and 8x cross fire vs 16 and 4x ?

 

[bicycle_repair_man]

Your motherboard is fine but make sure your PSU is up to scratch and that your case has good cooling and ventilation.

 

[nano__]

my psu is rm850 watt corsisr is any diffrent between crossfire 16x with 8x vs 16x with 4x ?

 

[bicycle_repair_man]

Your motherboard has two PCIe 3.0 x16 slots. Depending on what CPU you have and as long as you have no other PCIe devices, then both slots will run at x16 or x8.

PCIe 3.0 x8 is the equivalent to PCIe 2.0 x16 and the performance difference is negligible.

 

[nano__]

my cpu intel i7 6700k and psu rm 850 watt and the guide of motherboard about pci e is shown below
http://store1.up-00.com/2016-06/1465292624211.png

 

[bicycle_repair_man]

With that CPU, both PCIe slots will run at x8 speed, so you'll be fine.

 

[nano__]

so that mean when running crossfire on my motherboared (msi z170a m3) the pci e 16x and 4x will running 8x and 8x

 

[Tollman]

According to this list 390X CF will need a beefier PSU:
http://www.realhardtechx.com/index_archivos/Page362.htm

850W might be enough but you might want to look into it more to double check. A new PSU of the calibre recommended is a lot of money and might make upgrading nonviable. An 850w would likely have to work really hard too which lowers efficiency and may shorten lifespan? Not sure.

 

[nano__]

thank you , when i calculate the needed pc from a power the result was equal about 750 watt , but when the running 16x with 4x CF = 8X with 8X CF