PCIE x8 Gen3 or PCIE x16 Gen2?

[2wheels4kb]

My ASROCK Z270 SLI/AC is forcing me to run my GTX 670 FTW at Gen2 if it is installed in the PCIE x 16 top slot, or I can run it in the 2nd PCIE x 16 slot which is really PCIE x8 at Gen3. What's better?

CPU = i7 7700 (OEM Fan and Heatsink)
RAM: GSKILL 16GB DDR4-2133 (8GB x 2) Ram listed on ASROCK site as compatible
HD = 1 - 240GB SSD (Windows), 1 - 525GB SSD (Programs/Data)
OD = SATA DVDRW

 

[clutchc]

Rather than answer your question, I have one of my own. Both PCIe x16 slots slots on that board should be PCIe x16 @ 3.0... @ x8 lanes when used in SLI.
https://www.asrock.com/MB/Intel/Z270%20Killer%20SLIac/index.asp#Specification

Why do you think the 1st slot is only x8 lanes?

 

[2wheels4kb]

1st (top) PCIE x16 slot is x16. 2nd (Bottom) PCIE x16 slot is only x8 (only 8 physical lanes). This is stated in the motherboard "Quick installation guide".


If you re-read my post...

"My ASROCK Z270 SLI/AC is forcing me to run my GTX 670 FTW at Gen2 if it is installed in the PCIE x 16 top slot, or I can run it in the 2nd PCIE x 16 slot which is really PCIE x8 at Gen3. What's better?"

... you see card runs at gen2 on top PCIE or gen3 on bottom PCIE, thus x16 at gen2 or x8 at gen3.

 

[2wheels4kb]

Also Nvidia control panel lists it as "Bus: PCI Express x8 Gen3"

 

[Wolfshadw]

Motherboard Manual pg. 21 shows all expansion slots at Gen 3. As to your question, which is better 2.0 @ x16 or 3.0 @ x8, the answer is they should perform exactly the same. 3.0 @ x8 has half the PCI-E lanes, but twice the throughput as PCI-E 2.0.

-Wolf sends

 

[2wheels4kb]

Motherboard manual pg. 21 is confusing. It states that PCIE2 and PCIE4 are PCIE 3.0 x16.
Then is says for single graphics card install, PCIE2 is x16 and PCIE4 is N/A.

It also says that...

PCIE2 is "used for PCI Express x16 lane width graphics cards" then below that

PCIE4 is "used for PCI Express x8 lane width graphics cards".

When you run SLI in this board you have x8 / x8, not x16 / x16.

When I install my GTX 670 FTW in PCIE2, I have to run it at Gen2. If I run it at Gen3 or Auto, the system repeatedly crashes (loud noise, computer freezes, system reboots). If I put the GTX 670 FTW in PCIE4 it runs fine in Auto and NVIDIA control panel lists it as PCI Express x8 Gen3.

Motherboard has been issued an RMA and will be returned. Ordering a different board.

Thanks for the help.