ASUS Z77 Motherboard UEFI BIOS Tuning Guide

Internal PLL Overvoltage:

Increases internal phase locked loop rail voltage, allowing higher processor core frequency overclocking. A setting of Auto will enable this setting for you as you increase the CPU core multiplier over a certain threshold.

Most good processor samples will not need this setting enabled until overclocking past a core multiplier of 45X (4.5GHz CPU speed).

The stability of S3 sleep resume may be affected with this setting “Enabled”. If you find that your CPU won’t overclock past 4.5GHz without this setting Enabled, then the only choice may be to run at a lower speed if you find the system is unable to resume from S3 successfully.

CPU bus speed: DRAM speed ratio mode:

This setting is for Ivy Bridge processors only. This can be left at Auto to apply changes in accordance with the Memory Frequency setting.

Memory Frequency:

Selects the desired memory operating frequency (memory ratio). This setting is a derivative of BCLK and CPU bus speed:DRAM speed ratio mode. The target operating frequency is displayed within the drop-down list of this setting as well as the topleft corner of the Ai Tweaker menu.

Ivy Bridge CPUs have a wider range of memory ratio settings at their disposal than the previous generation Sandybridge processors. When used in addition with BCLK*, this allows more granular bus frequency control which should help us to tune a system to its full potential.

For daily use, we recommend opting for memory kits specified at a maximum of DDR3-1600.

Higher speed memory shows miniscule performance gains in most desktop software, so it is wiser to spend money elsewhere on the system. Further, the stability of the system at higher operating frequencies cannot be guaranteed, often interfering with resume from sleep states and also when the system is stressed by software. Hence our advice to opt for memory kits that are within processor specifications if you do not wish to spend time tuning the system for stability.

At the other end of the spectrum, benchmarking fanatics will find that 2GB PSC based kits offer the best overall performance in memory sensitive benchmarks. Target operating frequencies between DDR3-2400 to DDR3-2600 seem to be the optimal point for best scores and times in sensitive benchmarks utilizing CAS 6 or 7 timing sets, in tandem with sub-zero cooling of both the processor and memory modules. Higher speeds are possible at the expense of secondary and third memory timing parameters, often at the expense of efficiency. If PSC based kits are not available, then Samsung based kits offer a modern alternative albeit requiring looser operating latency at equivalent frequencies.

*Within functional limits of the BCLK setting.

iGPU Max. Frequency:

Sets the operating frequency of the on-die GPU.

EPU Power Saving Mode:

Auto adjusts system operating frequency and voltage regulation settings in order to save power. This setting should only be enabled at stock processor operating frequency. For all overclocking use, a setting of Disabled is recommended.

OC Tuner:

When enabled will run a series of stress tests during the POST-Boot process in order to auto-overclock the system. The final overclock will vary according to system temperatures and the memory kit used. Enable only if you do not wish to manually overclock the system.