Crossfire support

[Gas_Mask_]

So I was wondering why the Asus M5A99FX pro R2.0 has support for 4 way crossfire support, but the Crosshair 5 Formula-Z only has support for 3 way? Is it because of the x16 lane bandwidth difference?

 

Links to both:

 

M5A99FX pro R2.0: http://www.asus.com/us/Motherboards/M5A99FX_PRO_R20/overview/

 

Crosshair 5 Formula-Z: http://www.asus.com/us/Motherboards/CROSSHAIR_V_FORMULAZ/overview/

[TheSLSAMG]

The M5A99FX Pro R2.0 only supports 2-way CFX if we're talking R9 290/X, 3 way if we're talking anything below I think. "Quad-GPU" refers to dual-GPU cards.

 

The Crosshair 5 Formula Z supports 3-way CFX/SLI.

[Jumper118]

The M5A99FX Pro R2.0 only supports 2-way CFX if we're talking R9 290/X, 3 way if we're talking anything below I think. "Quad-GPU" refers to dual-GPU cards.

 

The Crosshair 5 Formula Z supports 3-way CFX/SLI.

this is correct. to have 4 way on either of them you would have to use dual gpu cards

[-rascal-]

The 990FX chipset technically can support 4-way CrossfireX, but most motherboards are not laid-out to do so. Besides, a standard ATX-sized motherboard only has 7 expansion slots. To install 4 separate cards, you'd need 8 slots.

 

The PCI-E slots on the M5990FX PRO R2.0 are spaced out so you can do 2-way Crossfire/SLi.  There is a full slot's space in between the two cards to help with ventilation / airflow between the two graphics cards. You can still two triple-slot graphics card if you wanted.

 

The Crosshair V Formula-Z is laid-out so you can do 3-way CrossfireX/SLi with dual-slot cards. With two graphics cards, you have a larger space between the two cards...you could use the middle PCI-E x1 or second red PCI-E x16 slot for another expansion card (i.e. sound card). You CANNOT install two triple-slot graphics cards on this motherboard -- trust me, I thought about getting two triple-slot cards with this motherboard; doesn't work.

[i_build_nanosuits]

pcie 2.0 at x8/x8 is already a bottleneck to higher end GPU's...those are meant to crossfire lower end cards such as the R9 270 for example...proof? here:

 

http://www.anandtech.com/show/5458/the-radeon-hd-7970-reprise-pcie-bandwidth-overclocking-and-msaa

Moving from PCIe 2 x16 (8GB/sec) to PCIe 2 x8 (4GB/sec) does incur a generally small penalty on the 7970. However like most tests this is entirely dependent on the game itself. With games like Metro 2033 the difference is non-existent, while Battlefield 3 and Crysis only lose 2-3%, and DiRT3 suffers the most, losing 14% of its performance. DiRT3’s minimum framerates look even worse, dropping by 19%. As DiRT3 is one of our higher performing games in the first place the real world difference is not going to be that great – it’s still well above 60fps at all times – but it’s clear that in the wrong situation only having 4GB/sec of PCIe bandwidth can bottleneck a 7970.

 

Ultimately what is clear is that 8GB/sec of bandwidth, either in the form of PCIe 2 x16 or PCIe 3 x8, will be necessary to completely feed the 7970.

 

So as you can see you can't even properly run dual HD7970 (R9 280X) on this...let alone 3 or 4 flagship cards like that.

[Gas_Mask_]

Thank you! (To all)