Asus Z77 line motherboards and PCI-E limitations

[Cyber Akuma]

I have an IBM ServeRAID M5014 RAID card, it uses PCI-E 2.0 x8. Although I am only going to be using four SATA HDDs in it in RAID5, so it will not be operating at anywhere near capacity.

I am planning to put it in a gaming rig which I am still finalizing the hardware on although I have decided to go with an i7 3770K CPU. So far my motherboard choices are between the ASUS Sabertooth Z77 and ASUS P8Z77-V Deluxe based on the OCT 2012 motherboard review on this site.

The main reason I am also considering the deluxe is because that is a server-class RAID card (Even though its a re-branded LSI) and is somewhat picky about what desktop motherboards it will work in (Namely, it's only officially supported in for IBM servers). I know that it will work on nearly any P8Z77 line ASUS board, but although the Sabertooth is a Z77 board, I don't know if it counts as a P8 line model. (Personally, I like the Sabretooth more than the Deluxe, not to mention its much cheaper.)

On top of that, since this will be a gaming rig, I am a bit worried about the fact that I am going to be forced to either make the RAID or 3D card operate at below it's specs. Both motherboards have two PCI-E 3.0 x16 ports, but they only operate at x8 if both are used at once. Not a problem for the RAID card, but this would make my 3D card suffer (although I have no idea by how much, I am still researching which 3D card to choose, it will likely be a GTX model though).

The Deluxe however has an additional PCI-e 2.0 x4 port, which would let me use the 3D card at a full x16 lanes but then my RAID card suffers at x4 lanes instead of x8. And although as I said before I am not operating it at anywhere near capacity (its meant to work with up to 32 SAS drives, and I am only using it with a SAS to SATA breakout cable for four) I am worried that I am already basically jury-rigging a server card to work on a motherboard its not supposed to, and that putting it on a x4 slot instead of x8 is asking for trouble.

I know this is a pretty unorthodox question, but does anyone have any advice?

[Astra.Xtreme]

Nothing comes close to maxing out 8x. Well I guess if you have 4 GTX 680s in SLI, then you'll max it out, but for your purpose, you have nothing to worry about.

[+PeterUK MVC]

About PCI-Express Scaling.

http://www.techpowerup.com/reviews/Intel/Ivy_Bridge_PCI-Express_Scaling/1.html

Since graphic textures are loaded to the GPU memory the bandwidth link is to get more from RAM or CPU tells it what to do for the GPU to display stuff this then mostly comes down to how optimised the game is for maxing out the GPU memory so that its ready to be used ahead of time.