F3-2666C11D-8GTXD not running at rated speed

[Delta7B]

F3-2666C11D-8GTXD not running at rated speed:

I just put together a new system and my g.skill memory won't run at 2666 MHz. I have an ASUS Maximus VII Hero motherboard with an i5-4690K cpu. I've tried with the CPU at stock settings and overclocked to 4.5 GHz. The memory will run stable at 2400 MHz, but at 2666 MHz the system continuously reboots early in POST. I have enabled XMP and it displays the correct speed and timings, and I have set the memory voltage to 1.65 V.

Please review my BIOS settings to see if there is something else I can do to make the memory work at the rated speed and timings: (not sure how to add images, tried to use the paperclip to attach them.)

[emissary42]

If you start with UEFI defaults and just enable the XMP, does the memory then run stable at those settings?

I am asking because raising the memory speed above a certain point does impact the voltages needed for a certain CPU overclock. So you probably have to redo your CPU overclock from scratch with the memory @ DDR3-2666 and might also have to manually adjust VCCSA and VCCIO(a/d).

[Delta7B]

Yes, I tried using the BIOS defalts with XMP enabled but it wouldn't get through the POST. Where in the BIOS are the two voltage settings you mentioned? I've looked for them but didn't locate them.

Thanks for the response!

[Delta7B]

I found these two settings, do they sound like VCCSA and VCCIO?

CPU System Agent Voltage Offset

CPU Analog I/O Voltage Offset

If so, are there recommended voltages I should try?

Thanks again.

[emissary42]

If the memory fails at XMP settings with the all other settings at default, i would test both modules individually and try to swap memory slots next.

http://www.kitguru.net/wp-content/up.../tweaker-3.jpg

VCCSA = System Agent Voltage
VCCIO(a) = CPU Analog IO
VCCIO(d) = CPU Digital IO

This should also be covered in any decent OC tutorial for LGA1150.

[GSKILL TECH]

Try manually setting the Systems Agent Voltage to 1.25V up to 1.30V.

Boost CPU VCore and DRAM Voltage a little to see if that helps.

If not, the CPU may not be capable. Generally an i7 CPU is necessary for DDR3-2666+