PCIe question

[fastman]

I'm looking at the GIGABYTE Z170X Gaming 7 with a i7 6700K CPU for a new rig.

As I read the specs on the slots below:

1 x PCI Express x16 slot, running at x16 (PCIEX16)
* For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16 slot.
1 x PCI Express x16 slot, running at x8 (PCIEX8)
* The PCIEX8 slot shares bandwidth with the PCIEX16 slot. When the PCIEX8 slot is populated, the PCIEX16 slot will operate at up to x8 mode.

Looking at a new card too, unknown flavor of a 1080 Nvidia likely.
Finally, a new SSD also and was thinking of the PCIE version.

So my question is will the system be hampered if I use the second x16 slot for the SSD?

Can I use the M.2 Socket for the SSD to get around this "limitation" or is it just a different interface to the BUS?

Thanks

 

[Pandasaurus]

The M.2 slot will still use PCIe lanes. With Skylake/Z170, you get 16 lanes off the CPU, and however many off the chipset (I don't remember how many Z170 has). The GPU should (theoretically) use the 16 off the CPU, then whatever other devices (SATA drives, M.2, etc) will use the lanes from the chipset.

 

[Smoblikat]

You wont really have any performance loss doing that. Thats still plenty of bandwidth for both devices.

 

[Mark R]

On the Z170X, the CPU provide 16 lanes of PCI-E, and the chipset provides 20 lanes.

The 2 GPU PCI-E slots are connected direct to the CPU. If only one slot is used, all 16 lanes are connected to the single slot. If both slots are used, 8 lanes are routed to one slot, and 8 lanes to the other.

The chipset connects the LAN, SATA, M2, etc. to its 20 lanes, so using an M.2 SSD uses a different route for getting data to the CPU - this will allow your graphics card to run at full speed.

Note that some of the PCI-E lanes used for M.2 are also used for SATA, and only one system can be used at a time. Adding an M.2 SSD may disable some of the SATA ports.

 

[mv2devnull]

Note that some of the PCI-E lanes used for M.2 are also used for SATA, and only one system can be used at a time. Adding an M.2 SSD may disable some of the SATA ports.

And/or some additional PCIe slots. Everything else (but the two "x16" slots; 16/0 or 8/8 direct from CPU) on the board is connected via the chipset, but there are more potential devices than lanes.

Some boards have "4 lanes to M.2 or to SATA/SATA Express ports x-y".
Some boards have "4 lanes to M.2 or to one PCIe x4 slot or to four PCIe x1 slots".


The real question is, which is worse:
A) Use direct to CPU slot for SSD and demote 1080 to use only x8 PCIe 3.0 channels, which is still quite a lo of bandwidth.
B) Use x4 via chipset for SSD connection and leave some other (unneeded) connectors disabled.

 

[bonehead123]

You WILLlose 2 SATA ports for each m.2 slot you use. There are a total of 8 available on this board, so if you use an SSD in 1 of the 2 m.2 slots, you still have 7 other sata ports still functional for any HDD's/ODD's etc.....just be sure to connect them to the active ports instead of the disabled ones

This does not disturb your x16 slots, but as others have said, if you use both of them (1 for GPU, 1 for SSD), they will both run at x8, which is more than enough bandwidth unless you are doing some really super-heavy duty crunching....

 

[Deders]

Note that some of the PCI-E lanes used for M.2 are also used for SATA, and only one system can be used at a time. Adding an M.2 SSD may disable some of the SATA ports.

You WILLlose 2 SATA ports for each m.2 slot you use. There are a total of 8 available on this board, so if you use an SSD in 1 of the 2 m.2 slots, you still have 7 other sata ports still functional for any HDD's/ODD's etc.....just be sure to connect them to the active ports instead of the disabled ones

This is only the case for Sata Express based M.2 drives, not PCIe based M.2 drives like the Samsung 950 Pro.

Basically so long as you don't use either of the 2 main 16x PCIe slots that are connected to your CPU's pcie lanes for anything but your GPU, you won't lose any GPU bandwidth.

 

[mv2devnull]

The GIGABYTE Z170X Gaming 7 has two M.2 connectors.

On the page 10 (section 1-2) is written: "The PCIEX4 slot shares bandwidth with the M2H_32G connector. The PCIEX4 slot will become unavailable when an SSD is installed in the M2H_32G connector."

On the page 32 (section 1-10) of the motherboard manual are tables showing how SATA-ports are affected by M.2 devices. They do show that the M2D_32G connector is mutually exclusive with many SATA ports, but the M2H_32G connector is not (except with SATA M.2 drive or when using RAID mode.)

 

[fastman]

You WILLlose 2 SATA ports for each m.2 slot you use. There are a total of 8 available on this board, so if you use an SSD in 1 of the 2 m.2 slots, you still have 7 other sata ports still functional for any HDD's/ODD's etc.....just be sure to connect them to the active ports instead of the disabled ones

This does not disturb your x16 slots, but as others have said, if you use both of them (1 for GPU, 1 for SSD), they will both run at x8, which is more than enough bandwidth unless you are doing some really super-heavy duty crunching....

So I looking to build a system like yours, except using only one Samsung 950 PRO m.2 pcie 256GB.

This will be for games and photo editing, you see no problem still?