Originally Posted by owcraftsman
Yes anything over 1333 is beyond default. All you have to do is set optimized defaults in bios with any dimm pair or 4x dimm population for that matter to see what a SB or Ivy defaults at on a Z68 chipset. it will generally default to 1333 or in some cases 1066. This is a platform limitation as evidenced by looking at a block diagram of the z68 platform. Note in the image below pulled from the Intel site where it clearly shows the default DDR3 1333.
It has been confused a bit by Motherboard Mfg because they list anything over 1600 as (OC) partly due, I suspect, to the fact none of these boards have trouble running the 1600 spec but in actuality 1333 is the default and you have to make a manual adjustment or engage the XMP mode to get anything over 1333 which is overclocking the systems memory.
I see no good reason to run your CAS 7 memory at CAS 9 even with all four dimm slots populated unless you have a very poor proc IMC which I doubt it's that bad. In most cases I have experimented with, all that's generally required to get running all four dimm slots at the modules rated spec is a vdimm & vccio bump and in very few cases a minor Vcore bump (not likely). I'll take 1.5v rated dimms and apply 1.65vdimm (generally accepted max vdimm most mfg's) (definitely Intel max vdimm spec for SB procs). Then I'll bump vccio to between 1.1 to 1.2(max) to achieve the desired results. Other than that I use the XMP default timings by enabling XMP mode one time for the sole purpose of taking note of the default timings for a given module so I can turn around and set those timings manually in bios. Occasionally I will also have to lower the command rate from 1t to 2t to run stably which all depends on the specific pairs you are using. To error on the safe side use 2t at first setup to avoid the headache as there is very little if any performance decrease with the setting. If you follow this advice I see no reason why they could not be running at the rated speed of your modules as long as they are identical pairs & same revision number. GL and let us know how it goes.
The weird thing is that my mobo defaults to 1600 when I set it to Optimized Defaults.
After setting to XMP, populating all 4 DIMMs would not even let me boot my computer actually. But I will try your suggestions of increasing VCCIO and VDIMM and see how it goes. And yes my kits are all the same, two kits of the same type. My bad, they are actually 1600MHz 6-8-6-24-2N modules, so CAS6 rated. Can I still run them at CAS6?
When you say bump VCCIO between 1.1 to 1.2V, should I do a stability test per increment and go with the lowest voltage I could be stable at?
These are my kits: http://www.memoryc.com/computermemory/ddr3/4gbgskillddr3pc3128001600mhzripjawsxseriesforsandybridge68624dualchannelkit.html
. They run at their rated spec when only 2 modules (1 kit ) is installed individually. But when you populate all 4 DIMMs, then I can't even boot at their rated spec.
Oh by the way, do you even use the Ai Tweaker\CPU Power Management tab when overclocking your CPU? Do you tinker with the CPU Ratio and Additional Turbo Voltage parameters?
EDIT: I have tried increasing VDIMM to 1.65V, VCCIO to 1.2V and set CAS settings to 6-8-6-24-2 and have problems booting the system again. When I set the CAS settings to Auto they default at 9-8-9-28-2, what seems to be the problem here?
Originally Posted by TwoCables
The reason for 1066/1333 being the default is that's the natively-supported DDR3 speeds for Sandy Bridge.
For example, see the "Memory Types" here: http://ark.intel.com/products/52210/Intel-Core-i5-2500K-Processor-6M-Cache-up-to-3_70-GHz
It says "DDR3-1066/1333". However, not every motherboard will default faster memory than this down to either 1066 or 1333 because many motherboard are designed to default to something else like DDR3-1600.
Ivy Bridge's "Memory Types" says "DDR3-1333/1600".
Like what I said above.Edited by kevindd992002 - 1/14/13 at 4:33pm