Top positive review
Make sure you don't get an early one w/a bad controller.
Reviewed in the United States on November 27, 2014
SATA5 and SATA6 ports can be used for four different things... Vanilla SATA ports; part of an Intel raid array, combined into an M.2 SSD port, or combined into a SATA Express port. The SATA Express port can be very fast, 10 Gb/s & the M.2 is a Gen3 x4 implementation capable of a blazing 32 Gb/s. Apparently some early motherboards have a controller that isn't up to all these combinations and permutations...
This is a difficult review. Over the years I've had several different MSI motherboards (P45, P965, & Big Bang Trinergy) & each worked satisfactorily & got replaced as part of an upgrade. Then I upgraded to a motherboard from a different vendor & while it's not obsolete, I've had so many problems that I decided it was time for something I could trust to work. The X99S arrived & it booted no problems & I upgraded to the most recent BIOS. The CLICK UEFI bios worked well & while it didn't recognize my Bluetooth mouse, the keyboard arrow keys sufficed. All of the previous motherboards have supported six drive Intel raid5 arrays & this one is supposed to also on ports SATA1 thru SATA6. The first time I booted it saw the drives on SATA1 thru SATA6, but on the first reboot, SATA5 & SATA6's drives disappeared & it was impossible to configure a five or six drive raid5 array. I checked & found 3 other users on MSI's forum & another 2 on a different site that had the same problem. MSI Technical Support wanted me to RMA the board, but I felt it was a BIOS problem & a BIOS revision would solve the problem. Four back & forths latter complete with lots of screenshots, Tech Support wrote "HQ was unable to duplicate the issue and believes this is a case of a bad controller on the board and we should RMA the board for replacement." So I sent it off to MSI. Tech support was very helpful & MSI has a really cute RMA status site that kept me apprised of its progress & had the replacement on the way back to me in a week.
The replacement arrived & it was a whole new box w/everything, not just the board. First Class! The box's lettering was a dark gray vs the originals near white, the SN contained B1410 vs the originals B1408, bios 1.3 was installed vs the originals 1.0, and best of all, six drive raid 5 works! Initializing a six drive array made of 1TB disks is fairly quick, 18 hours, but six 3TB disks took 116 hours, almost five days. Fortunately they can be quick formatted & a little stuff put on them long before the initialization is complete.
I guess anybody can have problems when a new CPU, support chipset & memory type come together for the first time, but all's well that ends well...
configuration: i7-5820k, Zalman LQ310 water cooler, 4 Crucial Ballistix 4GB 2400 DDR4s, MSI R9 270X Gaming 4GB, Seiki SE39UY04 39" 4k display, Crucial M4 256GB SSD (C:), 6 Seagate 3TB ST33000650NS hard disks (13.6TB Raid5, junction point C:\Users-D:\, another story, but it works!), 2 LG WH10LS30 Blu-Ray drives, a NETIS AD-1103R Ethernet adapter, & PC Power & Cooling Silencer Mk III 500W ATX12V Power Supply. Everything I read says I need a bigger power supply, but two different power meters say the system only draws 155/205/127 ave/max/min Watts & I already had the power supply. Yes, I really expected a much higher power draw.
May 29, 2015 update: I added another four Crucial Ballistix 4GB 2400 DDR4s to get up to 32GB & upgraded to Win7 Professional as Home Premium only supports 16GB. I haven't encountered any problems in the last six months & I'm a happy camper.
Sep 20, 2015 update: Samsung released their blazing fast second generation SM951 Gen3 x4 SSDs in three sizes, small/128GB - MZVPV128HDGL-00000, medium/256GB - MZVPV256HDGL-00000, & large/512GB - MZVPV512HDGL-00000 (they are hard to find; be careful & don't get the last of the first generation SM951 parts) & I went for the mama bear size. It turns out that Microsoft includes NVMe support on the Windows 8.1 & 10 installation DVDs, but not 7. Boo-Hoo... 7 users have to figure out how to install not one, but two hotfixes (Fix487764/KB2990941 & Fix3366972/KB3087873, Google KB2990941 for the details). Anyway, I made it through the Fire Swamp with its fire sprouts, lightning sand, and Rodents of Unusual Size & it really is blazing fast. This motherboard was ready for the future from the git-go, but if I was buying today, I'd go for the next generation - the MSI X99A SLI Plus.
Jan 6, 2018 update: I haven't encountered any problems in the last fifteen months & I'm still a happy camper.