ASUS Z77 Motherboard UEFI BIOS Tuning Guide

Misc Memory Settings

MRC Fast Boot:

Bypasses longer memory training routines during system re-BOOT. Can help speed up BOOT times. If using higher memory frequency divider ratios (DDR3-2133 and over), then disabling this setting while trying to achieve stability can be beneficial. Once the desired system stability has obtained, Enable this setting to prevent the auto sensed parameters from drifting on subsequent system re-BOOTs.

DRAM CLK Period:

Defines memory controller latencies in conjunction with the applied memory frequency. A setting of 5 gives best overall performance though may impact stability.

Transmitter Slew & Receiver Slew:

A setting of around ‘3’ on Transmitter Slew may yield the best results or a good starting point with most DIMM. Tweaking these settings will require some time, but can extend overclocking headroom for DRAM frequency. It’s best to adjust one step at a time and then run a memory intensive benchmark or stress test to monitor for changes in failure rates to find the optimal settings.

After changing Transmitter slew, one should go through the same steps tuning Receiver Slew. Both settings should be tuned before relying on an increase of voltage.

MCH Duty Sense CHA & CHB:

These settings can be left on Auto most of the time. If experimenting, start at middle value of 15, check for impact on stability then move up by +2 and re-check. Tuning will be system and DIMM specific and depend on operating frequency.

CHA & CHB DIMM Control:

Allows a user to disable a channel without physically removing the DIMM. Leave on Auto unless experimenting or testing individual channels for stability.

DRAM Read and Write Additional Swizzle:

Leave these settings on Auto unless experiencing instability at high DRAM frequency. Toggling from enabled to disabled or vice-versa may help pass a benchmark where the DIMMs were otherwise unstable.