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Overclocking & Final Thoughts
Motherboard companies used to sneak in a little extra DIMM voltage to overcome problems with a certain manufacturer’s “golden” RAM, but some of these firms have recently become extra-aggressive in order to win the overclocking portions of reviews. Memory companies have been watching this development, and some have come to rely on that extra voltage to sell “faster” memory that isn’t really “better” memory.
| EVGA Z170 Classified BIOS Frequency and Voltage settings | |
|---|---|
| BIOS | 1.04 (08/25/2015) |
| Base Clock | 100-340 MHz (5 kHz) |
| CPU Multiplier | 8x-83x (1x) |
| DRAM Data Rates | 800-4133 (100/133.3 MHz) |
| CPU Vcore | 0.80-2.00 V (1 mV) |
| System Agent | 0.70-2.00 V (1 mV) |
| CPU I/O | 0.95-1.80 V (1 mV) |
| PCH Voltage | 1.00-1.60 V (1 mV) |
| DRAM Voltage | 1.20-2.00 V (1 mV) |
| CAS Latency | 5-31 Cycles |
| tRCD | 5-63 Cycles |
| tRP | 5-63 Cycles |
| tRAS | 10-127 Cycles |
The Z170 Classified is the worst offender in this regard, producing 1.42 volts at the module at its 1.35V setting, but maybe EVGA didn’t need to be that aggressive? Even at the board’s 1.29V setting, which produces 1.35V at the DIMM, the Z170 Classified produced the highest four-DIMM overclock achieved to date on these memory samples.
Removing a couple modules to seek a higher dual-DIMM data rate didn’t work, but 3434 MHz is still solid for two modules. To top it off, the Z170 Classified reached this CPU’s record 4.6 GHz achieved by only two competitors thus far, and beat all competitors in BCLK overclocking. We did have a few minor problems with the board’s lack of boot failure recovery mode, but a press of the CLR_CMOS switch usually got us up and running.
One might expect a board with such high memory overclocks to rate poorly on overclocked bandwidth, since so many motherboards are programmed to reach higher data rates by using worse timings, yet the EVGA Z170 Classified excelled in this test. Perhaps, rather than use timing tricks to reach high clocks, EVGA designed a stabler memory bus? Trace layout and voltage regulation play big roles there.
But what about that big expensive PCIe switch that adds 4-way SLI capability? What effect does it have on performance?
Remember that while the Z170 Classified’s top slot is fed by all sixteen CPU-based PCIe 3.0 lanes, only eight of those lanes go to the PEX 8747 switch. As with less elaborate solutions, plugging a card into the second slot causes the board to redirect half the lanes of the first slot, feeding each card with eight lanes of bandwidth. Unlike those less-elaborate configurations, software will always detect the second card’s x16 connection to the PCIe switch in spite of the switch’s x8 bandwidth. The switch also imparts latency. Because any card in the second slot will have only eight lanes of the CPU’s bandwidth, the only fair way to evaluate the effect of switch latency is to compare it to the CPU-direct connection in x8 mode.
Our tests show that a GTX 970 user can expect an approximate 2-3% performance loss by switching from PCIe 3.0 x16 to PCI 3.0 x8. Connected at x8 on the Z170 Classified, the PEX 8747 can’t make up that bandwidth even after doubling the number of connections between it and the graphics card, and comes up around 5% short of the pure x16 connection. In other words, the controller imparts a 2-3% performance penalty of its own.
This is an unavoidable minor penalty for those who seek the graphics performance of 3-way or 4-way SLI with the clock speed and IPC of a Skylake CPU.
Final Thoughts
So how does EVGA’s Z170 Classified stack up? It’s hard to quantify, given that we haven’t yet tested anything else in its price class, but it certainly did a fine job of overclocking. And then there’s that expensive 48-lane switch that allows users to configure 3-way and 4-way SLI. We’d love to see how EVGA’s use of it as a 40-lane switch, with eight of its input lanes unused, compares to the configurations of its rivals.
But EVGA has no rivals, at least near or below the price of its Z170 Classified. We’ve seen various boards that were supposed to compete for the 3-way and 4-way SLI market displayed at shows and in press releases, but none have appeared for sale. That’s a little hard to believe, given that the platform is two months old, yet the only other Z170 3-way SLI motherboard currently on the market costs $500.
Advertised “Quad SLI” models don’t count because that label typically refers to only two (dual-GPU) cards.
There are of course other ways to evaluate a product. An editor of another site once told me that comparative cost isn’t important, that each product must be evaluated based on its ability to fulfill its role. He implied that cost should only matter to the buyer, not the reviewer. Perhaps that reviewer works for an Apple site?
The Z170 Classified stands directly between high-end boards that don’t have the PEX 8747 controller (around $300), and the only other one that does ($500). It doesn’t have as many “other features” as some of its $300 competitors, but those board don’t do 3-way or 4-way SLI. Lacking any direct way to compare its price to its worth (and produce a value award), there is still one other award the Z170 Classified can get from us: Our general stamp of approval.
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Thomas Soderstrom:
Thomas Soderstrom is a Senior Staff Editor at Tom's Hardware, covering Cases, Cooling, Memory and Motherboards. Follow him on Twitter.
