Skylake Z170, U.2 and Sata - Lanes conflict?

Question

I am building a new PC, based on the Intel I7-6770K and Z170 chipset, using a Gigabyte GA-Z170X-Designare. I have a problem and could use some guidance whether this is related to lane configuration, or if the motherboard seems just broken.

In that MB are:

• One U.2 connected Intel 750 1.2TB disk by the on-board U.2 connector
• One EVGA GTX970 Graphics card in the x16 PCIe slot (only slot used)
• Three Samsung 2TB 850 EVO SSD's connected to SATA ports

There are no other add-on boards or cards. The 750 is attached to a native U.2 port (one reason I bought this board is it had a native U.2 port, not needing a daughter card).

I am not overclocking. It has 64GB G.Skill 3000mhz memory running at the native 2133mhz at present.

The built in Intel graphics card is enabled but not in use. The two Intel NIC ports are enabled but only one in use. Thunderbolt is disabled (mostly to eliminate it as an issue).

There are 6 built in SATA ports. In this configuration the manual calls for ports 2 and 3 to not be available (lanes consumed by the U.2 port) and indeed that is true, I cannot use 2 and 3.

The power supply (Silverstone 520W fanless) was working in another PC, I swapped it to this one because I like the silence. So I have reason to believe the PSU is stable and working.

My issue is that ports 0 and 1 are not working either. They are not, however, completely disabled - they are flakey. SATA port 0 will sometimes work for a few minutes, show the disk, then hang. Port 1 will almost never (maybe always never but I think I may have seen it once) show a disk at all.

The normal symptoms of connecting an SSD to those ports are:

• Bios will not show the drive in the SATA configuration at all, 90% of the time, though occasionally it shows up.

• Bios RAID setup will usually show the drive (though the SATA configuration does not), but it is not usable. Sometimes it will not show up either.

• Attempts at using the drive if seen, e.g. in windows, will just lock the drive up - event logs show warnings of resets, drive 100% busy in task manager, no access of any kind works, power off required (shutdown will hang).

I have used all three SSD's in all configurations and swapped cables, and also tried additional cables, different power cords, etc, hours of experimentation. It is definitely specific to the ports, with ports 4 and 5 occupied, the drives are completely stable over hours of running, benchmarks, formatting, etc. Port 0 has never run more than about 2 minutes when it would run at all.

I've reset the MB bios to defaults, tried various changes with no impact.

Here's my root question - after a lot of reading I THINK That these should work, that the U.2 port should only affect two ports 2 and 3. My GUESS is that this is a hardware or firmware issue, not something I can fix. But there's a lot of contradictory information about how lane assignments work, how GPU's impact the storage lanes (my take is they do not, for a single x16 GPU), and even in several places whether the NIC's affect the SATA ports.

Does anyone have solid knowledge of how this should work? Am I over-committed on lanes in some fashion? Is there some way to ensure I do not have some conflict I am not thinking of?

Or do I just have a non-working motherboard?

PS. The Intel 750 in the U.2 port is working fine, it has not had any issues during all the experimentation.

Answer 1

OK, I know this was not a well respected question, but I did not want to leave it hanging. I have continued experimenting and replacing hardware and understand most of this.

First, the U.2 port had nothing directly to do with the issue, nor does PCIe lane sharing.

The GA-Z170X-Designare has at least one bios bug (in F2) that caused confusion with the U.2 port's drive; the Bios mode selection (Other OS, Windows 8/10, Windows 8/10 WQHL) shows or hides (in the first) the CSM compatibility mode. That's appropriate. But the effects of CSM compatibility at the point it is hidden is remembered, and affects how UEFI mode is used for storage rom's. In experimenting to get the Intel 750 working, this invisible option would cause the drive to appear and disappear seemingly at random for what looked like identical settings (but were not), leading to my confusion that the U.2 drive had some kind of conflict.

The CSM option seems to work as expected, you just can't get to it without switching Bios modes. This was a distraction, not a root cause.

Anyway... two motherboards and five SSD drives later to make sure this was not simply broken hardware, I found that Sata port 1 (and sometimes zero) just does not work correctly with a Samsung 850 EVO 2TB drive. In the Bios' Peripheral page, Sata configuration, such a drive mounted there does not appear at all, but identical drives do on ports 4 and 5. Sometimes zero appears and sometimes not.

Note 2 and 3 are not available with U.2 occupied, as expected.

The only other drive I have available to try is a very old notebook SSD (also Samsung) which appears in bios just fine in port 1 - not sure if that's because of size, Sata Version, or something else.

None of the five EVO's I have are visible in bios when in port 1, regardless of cable and power cord, and regardless of whether alone or in concert with other ports (including U.2 in or out).

Interestingly, the bios has a Secure Erase for SSD option, and in it all EVO's in all ports show "Frozen", leading me to think the root cause is some bios/firmware issue with something specific to that drive.

Even though the SSD does not appear, it will usually (maybe 95% of the time) appear in Windows, but it will only run from that port in Sata II speed (CrystalDiskMark64 timings are almost literally cut in half). At least twice in testing the drive also disappeared while in use in Windows, so the issue is not limited to bios visibility.

The same behavior occurred on two different motherboards. I also found an F3a version of the bios (not yet released) that had the same behavior as well. A support ticket with Gigabyte after about 10 days has made no progress other than "RMA to vendor".

So while I do not know the root cause, the issue seems a specific combination of this motherboard's design or bios, and some aspect of a Samsung 850 EVO 2TB drive.