When talking about 5820K only supporting 28 Lanes.....

what uses up the lanes over and above the GPU(s)?
Any and all add in cards?
M.2 PCIe SSDs?
More devices pluged in to USB ports?
More Harddiscs plugged into Sata Ports?
Disabled onboard sound?
Onboard NIC?


How many lanes would an Asus X99-s with 5820K, 1x970 (HDMI Audio and Video), 10x Sata, 1x PCIeX4 M.2 SSD use?

If you needed more lanes can you configure a single GPU to be limited to x8 manually.

Want to check before buying 28 lane CPU.

thanks

Don't worry about it. Unless you're going tri-fire or more 28 lanes is plenty enough.

As far as I can tell it will only affect the PCI-E slots:

http://www.asus.com/uk/Motherboards/X99S/specifications/

40-Lane CPU-
5 x PCIe 3.0/2.0 x16 (x16, x16/x16, x16/x16/x8, x8/x8/x16/x8, x8/x8/x8/x8/x8 mode) *1
1 x PCIe 2.0 x4 (max at x4 mode) *2

28-Lane CPU-
3 x PCIe 3.0/2.0 x16 (x16, x16/x8, x8/x8/x8)
2 x PCIe 2.0 x16 (x1 mode)
1 x PCIe 2.0 x4 (max at x4 mode) *2

Click to expand...

28 PCI-E 3.0 lanes is ample for 99% of users, it was blown all out of proportion by a few AMD fanboys.

The notes at the bottom explain how other onboard resources are shared (or any other notable details):

*1: The PCIe x16_5 shares bandwidth with M.2 x4. Triple PCIe 3.0/2.0 configuration is default set at x8/x8/x8. Adjust PCIEX16_5 Slot Bandwidth in BIOS.
*2: The PCIex4_1, USB3_E12 and SATAEXPRESS_E1 connectors share the same bandwidth. The SATAEXPRESS_E1 will be disabled when there is a device installed on PCIEX4_1 slot. Set this option to X2 Mode or X4 Mode when the installed PCIe device is higher than X4 interface.
*3: Due to chipset behavior, The SATA6G_78, SATA6G_910 ports (black) do not support IRST including RAID configuration.
*4: These functions will work depending on the CPU installed.
*5: These SATA ports are for data hard drivers only. ATAPI devices are not supported.

Click to expand...

Each motherboard is different so it's best to go to the manufacturer website and look at the detailed specifications for each particular motherboard.

I do still want to understand, if even if its not an issue...

so in the asus example...
M2x4 would use 4 lanes, USB3_12 would use 1 lane..Sata dont use any lanes?
Onboard Sound would never use a lane and neither would LAN..enabled or disabled.?
add in cards would use the lanes assigned to slot by the bios configuration/specification above.?

I'm not sure how many lanes they use exactly, you'd have to ask Asus or calculate how much bandwidth they offer and make an educated guess. The thing is if a PCI-E 8x slot is sharing with a controller which uses only a single lane, if the controller is in use then the PCI-E slot will have to drop down to 4x because it can't run at 5x, 6x or 7x, the 3 missing lanes might get redirected or just left wasted.

Intel SATA, Intel USB, Audio and LAN etc are all connected to the southbridge via a separate DMI link so they aren't affected by 28 or 40 lane CPUs.

With that motherboard it looks like the ASMedia SATAExpress & ASMedia USB controllers are shared with the 4x slot, M.2 with the bottom PCI-E 16x slot, I'd say that the 4x slot is also connected directly to the southbridge.

This sharing will happen even if you have a 40x lane CPU, the main thing that the 28 lanes affects is the number of GPU's you can run. Unless you plan on using 3-4 GPU's and populating every single other PCI-E slot I doubt you'll have a problem.

an easy to use visual representation of 40/28 configurations

http://techreport.com/review/27279/asus-x99-a-motherboard-reviewed