MSI X99S SLI Plus, In Detail
The X99S SLI Plus' feature set is extensive enough to actually confuse us. To begin, it has all of those PCIe 3.0 switches that its competitors couldn’t afford to add, which enable combinations like three-way SLI and PCIe 3.0 M.2. The company then adds six more USB 3.0 ports through two add-in controllers, increasing the total port count (including two front-panel headers) to twelve, while competitors limit their USB 3.0 port count to six on any X99 model under $240. Did we mention that the X99S SLI Plus is usually available somewhere for less than $200? Hence our confusion. Does MSI lose money on these?
You’ll find a lighted CLR_CMOS button on the I/O panel in addition to the basic stuff. Sliding down the edge a little we also find another unusual feature (by budget-oriented board standards): a row of voltage detection points including both DIMM rails, CPU I/O, CPU core and PCH voltages. MSI doesn’t even mention this feature in its X99S SLI Plus user manual. As with the X99S SLI Plus’ ability to run a fourth PCIe x16 graphics card, it’s an “Easter egg”.
One capability that we always thought would be standard on ATX-based X99 motherboards is the second set of DIMM slots corresponding to each of the platform’s four channels. That’s eight slots. The only competing sub-$200 X99 board has four. Perhaps someone else thinks that buyers who can’t afford more than $200 for a motherboard won’t use more than four DIMMs. Perhaps they’re right. But any of us can appreciate the added expense of including the full set of slots.
Other internal features include a PCIe connector that extends the bottom two (outward-facing) SATA ports into SATA-Express, a dual-BIOS switch (next to the SATA-E interface), Power/Reset/OC Genie buttons just below the last PCIe slot and a total of five four-pin PWM-style fan headers. The OC-Genie button engages MSI’s automatic overclocking and validation routine without installing the bundled software application that does the same thing.
Two of the fan headers are found near the front and back of the bottom edge, two are near the front of the top edge and one is placed between the rear DIMM slots and I/O panel connectors to serve a case fan. Builders with two intake fans may need an extension cable to reach the farthest bottom connection.
Speaking of extension cables, I’ve never seen one for front-panel audio. That’s a shame, since the front-panel cables of some cases are just a little too short to reach the FP-Audio header in the X99S SLI Plus’ bottom-rear corner. This placement was specified by Intel around eighteen years ago, so builders who experience this problem should send a strongly-worded letter to their case manufacturer.
MSI places one front-panel USB 3.0 header above the top graphics card, along the front edge, so that it won’t get in the way. The company faces its second USB 3.0 header forward, so that its cable can tuck under the card. Eight of the ten SATA 6GB/s ports also face forward for the same reason.
MSI recommends that builders with 40-lane CPUs use the lowest slot to enable three-way SLI with x16-x16-x8 connections, though doing so has several drawbacks. First, there’s a good chance that a long graphics card in that slot will block the SATA-Express port (or the two SATA cables you might use there instead). Second, the same type of card will block the dual-BIOS switch, which might be a problem if you overclock too far. Third, a long graphics card probably won’t fit with a fan plugged into the bottom-rear fan connector. And other front-panel cables will likely need to be smashed flat against the tops of their connectors to seat that card. Finally, since the bottom slot shares four lanes with the M.2 connector, the connector’s PCIe 3.0 interface gets disabled. MSI still beats competitors by providing two back-up M.2 connections, PCIe 2.0 x2 and SATA 6Gb/s x2 (both through the X99 PCH). But there is a better option available. Instead of using the fourth x16-length slot for a third graphics card, we recommend using the third.
Why? The third PCIe x16 slot gets eight lanes from the first slot. That’s what makes it possible for a 28-lane CPU (the Core i7-5820K) to have three-way SLI (x8-x8-x8 mode) and PCIe 3.0 M.2 (x4 mode) simultaneously. Users of 40-lane processors would get the “odd” configuration of x8-x16-x8 with this card placement, but if that doesn’t bother you it doesn’t bother us either. The x8 slot is still your “limit”, whether you have one or two cards using it. And, at PCIe 3.0’s high transfer rate, we’ve yet to measure a limit from a x8 slot (or, in this case, two).
Unlike most reduced-cost motherboards, the X99S SLI Plus includes six SATA cables. On the other hand, it also has only one SLI bridge. Power users who want three-way SLI will need to find another one.