|BIOS Frequency and Voltage settings (for overclocking)|
|ASRock Z97 Extreme6||Asus Z97-Pro(Wi-Fi ac)||Gigabyte Z97X-UD5H||MSI Z97 MPower||Supermicro C7Z97-OCE|
|Base Clock||90-300 MHz (0.1 MHz)||80-300 MHz (0.1 MHz)||80-333 MHz (0.01 MHz)||90-300 MHz (0.05 MHz)||0-655.34 MHz (0.01 MHz)|
|CPU Multiplier||8x-120x (1x)||8x-80x (1x)||8-80x (1x)||8-80x (1x)||1-65534x (1x)|
|DRAM Data Rates||800-4000 (200/266.6 MHz)||800-3400 (200/266.6 MHz)||800-2933 (200/266.6 MHz)||800-3200 (200/266.6 MHz)||800-4000 (200/266.6 MHz)|
|CPU Vcore||0.80-2.00V (1 mV)||0.01-1.92V (1 mV)||0.50-1.80V (1mV)||0.80-2.10V (1 mV)||0-2.00V (1 mV)|
|VCCIN||1.20-2.30V (10 mV)||0.80-2.70V (10 mV)||1.00-2.40V (10 mV)||1.20-3.04V (1 mV)||1.85-2.40V (5 mV)|
|PCH Voltage||0.98-1.32V (5 mV)||0.70-1.40V (12.5 mV)||0.65-1.30V (5 mV)||0.70-2.32V (10 mV)||0.96-1.36V (5 mV)|
|DRAM Voltage||1.17-1.80V (5 mV)||1.20-1.92V (10 mV)||1.15-2.10V (20 mV)||0.24-2.77V (10 mV)||1.35-1.95V (5 mV)|
|CAS Latency||4-15 Cycles||1-31Cycles||5-15 Cycles||4-15 Cycles||3-15 Cycles|
|tRCD||3-20 Cycles||1-31Cycles||4-31 Cycles||4-31 Cycles||3-15 Cycles|
|tRP||4-15 Cycles||1-31Cycles||4-31 Cycles||4-31 Cycles||3-15 Cycles|
|tRAS||9-63 Cycles||1-63 Cycles||5-63 Cycles||9-63 Cycles||9-63 Cycles|
Our original Core i7-4770K was nearly perfect; we could push 4.7 GHz at something less than 1.30 V when we topped it with similarly strong cooling. After extensive tests, we eventually settled on 4.6 GHz at 1.25 V with a mid-sized thermal solution.
Intel’s Haswell cores haven’t changed much in spite of the new models, with a purportedly more advanced thermal material between the heat spreader and die serving as the most notable “Devil’s Canyon” advancement. Our new Core i7-4790K gets that improved TIM, but isn't one of the lucky few CPUs able to reach previously-unseen clock rates. Rather, it needs 1.28 V to hit 4.6 GHz. The only improvement, then, is that we don’t need perfect cooling to run at 1.28 volts.
ASRock and Supermicro sent in the highest-overclocking boards this time, with Supermicro achieving the same 46 x 100 MHz setting at noticeably lower temperatures. We’d like to credit its voltage regulator, but haven’t figured out a great way to test that part separately.
Asus didn’t reach 46 x 100 MHz without eventually crashing, but did push 4.59 GHz at 45 x 102 MHz.
Asus turned in the highest base clock at the top strap setting. Gigabyte’s Z97X-UD5H wouldn’t boot with the 1.66x strap enabled, though a few advanced settings might have helped. Our primary focus on BCLK rests with the 1.00x strap, since that’s where non-K CPUs are stuck, and the Z97S-UD5H leads there, followed by MSI’s second-place Z97 MPower.
ASRock’s Z97 Extreme6 leads the memory overclocking race, followed by Asus’s Z97-Pro(Wi-Fi ac).
In one of our memory reviews, we noticed that some of Asus’ top-overclocking boards suffer worse memory bandwidth at DDR3-2800 than at DDR3-2400 and decided that a DDR3-2800 memory bandwidth comparison might be a good idea. After all, what good is a top overclock if it ruins your performance?
Gigabyte has been kicked around in the past for not producing a top memory overclock (and for not having top bandwidth at ordinary data rates). But it would probably be more accurate to say that Asus starts out with optimized settings and applies heavier stability compensation as clocks are increased. Gigabyte’s Z97X-UD5H is the clear leader when DDR3-2800 performance is your priority.