Z270F and Intel 900P AIC

[lucazds]

Hi and Happy New Year everybody!
I kinda need your help guys.
I own an ASUS Z270F Motherboard paired with an Intel I7 7700K (which provides only 16 PCIE lanes).

According to user manual, the motherboard got the 3 following PCIE slots:
2 x PCIe 3.0/2.0 x16 (x16 or dual x8)
1 x PCIe 3.0/2.0 x16 (max at x4 mode)
4 x PCIe 3.0/2.0 x1

The first of the 2 PCIe 3.0 x16 slot is in use by nVidia GTX 1070.

I'm planning to install an Intel 900P PCI Express Add-In-Card HHHL (480GB) which needs x4 PCI-Express lanes.
I'd like to know if the installation of the Intel 900P in the x4 mode slot will cut half of the videocard bandwidth provided by the PCIE CPU lanes.
I explain myself better. Will the SSD perform with the PCIE lanes of the chipset, or will it 'eat' some bandwidth from my videocard?

Thanks in advance for your help.

Luca

 

[alexoiu]

Hi, Happy New Year, if installed in the x4 one, then it should use the chipset lanes.

 

[lucazds]

'It should', I think the same way you do.
I contacted ASUS support by mail and online chat. I've got 2 different answers: 1st guy (chat) said board would 'use' chipset lanes; 2nd guy (mail) answered both 5th and 7th slots (x8 and x4) would use CPU PCIE lanes.
Is there a way I can discover it?

Thanks.

L.

 

[alexoiu]

In the manual, they list only the first two slots sharing the CPU lanes. However, no noticeable impact on the card's performance in x16 vs x8, so I'd give it a try.

 

[lucazds]

You are right about the low impact (around 1% at the moment) between x8 and x16 bandwidth. But i'm not going to change MoBo and CPU before few years so I would like to let GPU (even fasters gpus in the future) get all the 16 dedicated lanes with ease hahaahhaahahah.
Can you please tell me how did you understand which slot use the pcie lanes from cpu and which not? Does it depend on IRQ diagram? I just want to be sure before buy that SSD! Thanks in advance.

 

[alexoiu]

The PCIe operating mode lists only the first two slots:
http://dlcdnet.asus.com/pub/ASUS/mb/LGA1151/STRIX_Z270F_GAMING/E12193_STRIX_Z270F_GAMING_UM_V2_WEB.pdf?_ga=2.233613853.2064269406.1514446776-536028261.1514446776
page 1-8.
Same for the settings in BIOS related to the PCIe slots. They are available for the first two slots only. Not 100% sure, though.