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Three Z97 Express Motherboards, $220 To $280, Reviewed

ASRock Z97 Extreme9

ASRock designs its Z97 Extreme9 specifically for users who need a relatively large number of high-end graphics cards to share the Z97’s relatively small number of PCIe 3.0 lanes. The so-called 48-lane PEX 8747 PCIe bridge makes this happen by repeating 16 lanes of input to 32 output lanes.

Though it shares a lot of connectors with the lower-cost Extreme6, ASRock’s high-end Z97 Extreme9 expands their functionality in several places. The Gigabit Ethernet ports are both driven by Intel parts, for example, and that allows them to work in tandem (Teaming mode). The Ultra M.2 connector doesn’t disable SLI on any of the other slots, as it did on the cheaper board. The mini-PCIe slot doesn’t steal a lane from any x1 slots either, since there is are no x1 slots on the Extreme9. In fact, the only really annoying carry-over from the cheaper platform is the two-lane x16-length slot, which is moved to the center position of the Extreme9.

One thing ASRock doesn’t tell anyone is how it gets all the flexibility for those four PCIe 3.0 slots without sacrificing its four-lane PCIe 3.0–connected Ultra M.2 slot. To begin, PLX’s “big” bridges include a feature called multicast, the technology that Nvidia previously referred to as Broadcast and the same tech I referred to previously as “repeating.” This type of bridge leverages the fact that every card in a CrossFire or SLI array receives the same data by repeating the data from one multi-lane slot (the bridge’s PCIe x16 input) to multiple cards.

Because the CPU still has 16 lanes and the PLX bridge needs all 32 of its output lanes to maintain a quartet of x8 slots (for four-way SLI), the x16 connection between the CPU and PLX bridge is the only possible place for Ultra M.2 to steal four PCIe 3.0 lanes. Since the hose side of the bridge only operates in x16 or x8 mode, total bandwidth drops to x8. Those eight lanes are still repeated to four slots, but “x16” mode for two or fewer cards only exists on the device side of the bridge whenever Ultra M.2 is utilized in PCIe mode.

ASRock knows how to produce a good layout, spacing all four PCIe 3.0 slots two spaces apart to allow four double-slot graphics cards to fit into an eight-slot case. Builders who choose two triple-slot cards instead gain access to the x16-length PCIe x2 slot in the middle, which should be perfect for all x1 and some x4 expansion cards. And ASRock even moves both USB 3.0 front-panel headers out of the path of any graphics card by locating them above the top slot, along the motherboard’s front edge.

The only two layout problems we see are the FP-Audio connector shoved all the way back into the Z97 Extreme9’s bottom-rear corner and the board’s eight-pin CPU power connectors close to the center of the top edge. The FP-Audio cables of some cases are slightly too short to reach that far into the corner, and the overhang of some CPU coolers will make CPU power connectors impossible to disconnect with the CPU cooler installed. Both issues are easily overcome by proper case and cooler selection.

Putting aside any minor layout concerns that involve cases and cooling, we also find a few features to help the Z97 Extreme9 live outside a chassis. On-board power and reset buttons are perfect for bench testing and overclocking exhibitions, a switch that allows manual selection between two BIOS chips adds even more overclocking flexibility (or at least recoverability) and socket mounts for both BIOS ROMs even allows solder-free repairs to any overclocker rushed enough to brick both ROMs. Oh, and the two-digit firmware code display comes in handy for figuring out where your mad-science overclock went wrong.

The Z97 Extreme9’s four SATA cables aren’t very extravagant for a 10-port motherboard, but ASRock does provide a motherboard-to-drive cable to power-cycle old hard drives that it thinks have been sitting idle for too long. ASRock calls this “HDD Saver” technology, and it’s controlled through firmware.

The Z97 Extreme9 also includes a trio of two-way SLI bridges and one three-way bridge. Anyone who can install a motherboard without the manual will probably be able to figure out how to make those three two-way bridges connect four graphics cards together, while those who rely on instructions will find this information on page 33 of the user’s manual.

Thomas Soderstrom is a Senior Staff Editor at Tom's Hardware US. He tests and reviews cases, cooling, memory and motherboards.