SLI and M.2 Utra on Taichi X99

Nick wrote: I have a Taichi X99 (latest BIOS) with 64Gb Corsair Dominator DDR4 @ stock speed (2800), an i7-6850K (40-lane CPU) no overclocking, 2x Nvidia Titan X (Pascal) in SLI driving 3 identical Asus Monitors, and 2x Samsung 950 Pro M.2 Ultra SSDs (one set as the UEFI boot drive is 256Gb in slot closest to the CPU, the other is 512Gb) running Windows 10 64Gb. All is well except for 2 things: 1. When I use the Samsung Magician Software to check my drives, the boot M.2 Ultra drive is utilizing the Samsung NVMe  driver at blazingly fast read/write speeds, but the other Samsung (512Gb) M.2 Ultra drive is listed as using AHCI (Not NVMe) and has much slower (like 4x less) read/write speeds. Since I have a 40 lane CPU, both M.2 drives should be operating at PCIe Gen3 4-lane speeds, correct? The only other cards I am using are the 2x Nvidia Titan X's, so if my math is correct thats x16+x16+x4+x4=40 lanes, right? I do have other SATA SSDs hooked up to the SATA ports, but not the SATA3_1 and SATA3_2 that are shared with the M.2 ports. What is going on here? 2. When I go into Nvidia Control Panel to setup/modify Nvidia Surround with SLI on, I notice that GTX Pascal card labelled as #1 is always the one in PCIe slot #4, and the card labelled as #2 is always the one in PCIe slot #2. I have tried switching the cards, etc but it always comes up in this configuration (I know this based on the 2 monitors hooked up to one card, and one monitor hooked up to the other in the control panel figures) I thought that Slot PCIe #2 (closest tio the CPU) was the dedicated default graphics slot (like the old days of AGP) and that any others were just accessory. The reason this is important is because I don't want to inadvertently set the same card in non-SLI that is doing the bulk of the graphics to also do Physx calculations. I have checked the system using AIDA64 and GPU-Z and both slots are listed as running at x16. It's just irritating that it isn't what I believe it should be. Any thoughts? Thank you very much. -Nick

First, the SATA ports shared with the M.2 slots are, from the X99 Taichi specs:

SSATA3_3 connector is shared with the M2_1; SSATA3_2 connector is shared with the M2_2

Those are two of the four SSATA3 ports, the secondary SATA ports that do not support RAID. These ports are at the top of the stack of SATA ports (two of them) and two more just below the C and D memory slots.

They are labeled SSATA3_0 to SSATA3_3, and are items 11, 13, and 14 in the Motherboard Layout page in the manual. The SATA3_1 and SATA3_2 are not shared with the M.2 ports

Your CPU has 40 PCIe lanes, so you have plenty for two video cards and two M.2 PCIe SSDs. It does not make sense that a 950 Pro NVMe SSD can be operating with an AHCI driver.

Samsung also has the XP941 and SM951 M.2 SSDs that are not NVMe drives, and use the standard MSoft AHCI driver for their onboard controllers. They are not SATA M.2 SSDs, and perform much better than a SATA drive.

Samsung also manufactures SATA M.2 SSDs, the 850 EVO is the most common. Where did you buy your two 950 Pros?

Does the Magician software identify both of your M.2 SSDs as 950 Pros? Did you click on the Authenticate button for each of them in the Magician software? It seemed strange to me that anyone would put an authenticate option in their software, but apparently Samsung has had fake SSD sold with their name on them.

In Device Manager, you should have two entries in Disk drives that say, "NVMe Samsung 950...".

Did you install the Samsung NVMe driver? You should have two entries in Device Manager, Storage Controllers, one for each drive, that are: "Samsung NVMe Controller". Otherwise you must be using the Microsoft NVMe driver which will be installed by Windows 10.

In the UEFI/BIOS, in the Tools screen, run System Browser and move the mouse pointer over each M.2 port, and see what is displayed.

Your board's latest UEFI version (1.40) might have, in the Advanced screen, an entry for the NVMe Configuration screen. All it does is list the NVMe drives detected. Check that if you have that screen available.

About your video cards, there is no concept of a dedicated graphics slot, or primary and secondary slots, particularly when 40 PCIe 3.0 lanes are available.

Actually, that is caused by having multiple PCIe x16 slots, that are also x16 electrically, connected to 16 PCIe lanes. What purpose would there be to restricting one x16 slot as primary, and the others as secondary, etc?

Other X99 board users have asked about this too. There is nothing you can do about it. The Nvidia Control panel software should have a better way of identifying each card.