|BIOS Frequency and Voltage settings (for overclocking)|
|ASRock Z77 Extreme6||Asus Z87 PRO||ECS Z87H3-A2X Extreme||Gigabyte Z87X-UD4H||MSI Z87-GD65 Gaming|
|Base Clock||90-300 MHz (0.1 MHz)||80-300 MHz (0.1 MHz)||99.5-300 MHz (0.1 MHz)||80-267 MHz (0.1 MHz)||90-300 MHz (0.1 MHz)|
|CPU Multiplier||8.0-120x (1x)||8.0-80x (1x)||16-80x (1x)||8-80x (1x)||8-80x (1x)|
|DRAM Data Rates||800-4000 (200/266.6 MHz)||800-3200 (200/266.6 MHz)||800-3000 (200/266.6 MHz)||800-2933 (200/266.6 MHz)||800-3200 (200/266.6 MHz)|
|CPU Vcore||0.80-2.00 V (1 mV)||0.001-1.92 V (1 mV)||0.00-2.00 V (1 mV)||0.50-1.80 V (1 mV)||0.80-2.10 V (5 mV)|
|VCCIN||1.20-2.23 V (10 mV)||0.80-3.04 V (10 mV)||-1 to +1 (Offset Only)||1.00-2.91 V (10 mV)||1.80-3.04 V (10 mV)|
|PCH Voltage||0.97-1.32 V (5 mV)||0.70-1.50 V (12.5 mV)||1.06-1.68 V (10 mV)||0.65-1.30 V (5 mV)||1.05-1.68V (10 mV)|
|DRAM Voltage||1.17-1.80 V (5 mV)||1.20-1.92 V (5 mV)||1.10-1.82 V (5 mV)||1.15-2.10 V (5 mV)||0.30-2.45 V (25 mV)|
|CAS Latency||4-15 Cycles||1-31 Cycles||4-18 Cycles||5-15 Cycles||5-15 Cycles|
|tRCD||3-20 Cycles||1-31 Cycles||4-18 Cycles||4-15 Cycles||5-15 Cycles|
|tRP||4-15 Cycles||1-31 Cycles||4-18 Cycles||4-15 Cycles||5-15 Cycles|
|tRAS||9-63 Cycles||1-63 Cycles||10-40 Cycles||5-63 Cycles||10-40 Cycles|
Most of the firmware ranges presented by today’s motherboards are extremely unrealistic, as LGA 1150-based processors are generally limited to around 10% base clock alteration (beyond base clock ratio changes) and a maximum DRAM data rate of 22x 133 MHz (2,933 MT/s). Higher memory multipliers aren’t supported by Haswell CPUs, but combining a functional multiplier with a higher base clock is still an option.
Gigabyte ties Asus for the highest CPU clock, with MSI trailing only slightly behind. ECS reaches 4.5 GHz, but I wasn’t able to prevent it from using the standard two-ratio drop to 4.3 GHz when loading four cores.
Asus and Gigabyte also have the highest base clock, though Intel told our editor-in-chief, Chris Angelini, that ratio selection isn’t available for multiplier-locked Haswells. Other boards had trouble using the 166 MHz ratio, though we don't see any practical reason to do so with our air-cooled Core i7-4770K.
ECS bragged to me that it had the best-overclocking motherboard, and when I told the company otherwise, it referred to memory data rate. Indeed, the Z87H3-A2X ties Asus’ Z87-Pro for top memory clock.