You are not registered yet. Please click here to register!
View Single Post - Asus X58 + 6/12GB memory overclocking - detecting less memory than installed
View Single Post
Old 17-09-2009, 01:10 PM   #1
eva2000's PC Specs
Join Date: Jul 22 2004
Location: Brisbane, Australia
Posts: 23,046 Facebook Page
Blog Entries: 42
Exclamation Asus X58 + 6/12GB memory overclocking - detecting less memory than installed

Intel Core i7 X58 platform can result in missing DDR3 memory or incorrect physical DDR3 memory amounts being reported. Reasons and solutions to fixing these mis-detected DDR3 memory issues are outlined below with the advice also applicable to running stable and optimal memory configuration settings for your particular X58 chipset motherboard. I urge you to read this info below carefully and for more extensive help, best to start your own thread in relevant Intel motherboard / cpu forum as listed here Don't forget to bookmark the shorter url which would be easier to remember at

Base starter settings"

If you must start from some basic settings, I'd recommend turning off XMP profiles and setting voltages and timings manually, basic CAS-TRCD-TRP-TRAS timings I'd start with is 9-9-9-24 2T with tRFC 110 and tFAW 31 to 39. Voltage wise from my experience, for 3x2GB configs > 160-180+ bclk and >1600mhz memory speeds, CPU VTT of 1.3-1.4v is needed depending on cpu IMC quality and cpu cooling used. 180-200bclk and >1800mhz memory speeds, CPU VTT 1.35-1.55v. For 200+ bclk and 1950+ mhz mem speeds CPU VTT 1.4-1.65v needed. For 6x2GB will need higher CPU VTT and VDIMM memory volts than 3x2GB configs. That should be loose enough to start with and you can work your way up to the values your memory is rated for via trial and error testing.

Ensure that you set AI OverClock tuner (for Asus boards) to manual and NOT AUTO or XMP and set Bclk, uncore (UCLK) and mem (DRAM) frequencies manually


So to start your own thread you have list of forums where to post as follows:

(I'd post what bios settings you have currently tried as well - some forums here have stickies with bios templates you can use to adjust to your boards format so you can fill in with your settings i.e. here and here and here)

Short URL Link for this page.

Across various forums, folks reporting sometimes that they detect less memory available in windows, bios, memtest86+/DOS, than physically installed. For example, installed 6GB or 12GB and only detecting 4GB or 8-10GB respectively.

I thought I'd outline some possible reasons for detecting less memory than installed:
  1. incorrect CPU VTT (uncore) voltage set - what Asus terms as QPI/DRAM voltage, Gigabyte terms as QPI/VTT while most other boards refer to it as CPU VTT voltages. Vdimm is DRAM Bus Voltage in bios.
  2. incorrect QPI/DRAM to VDIMM relationship - every cpu/mem pairing will have an optimal voltage differential between QPI/DRAM to VDIMM voltage usually between 0.01 to 0.5v difference. Fall out of the optimal differential voltage for cpu/mem pairing will = less memory detected and/or lower memory bandwidth reported compared to when optimal voltage differential is in place. You also want to read Intel Core i7 920 Overclocking Introduction Guide on X58 to observe some guidelines such as keeping Uncore memory frequency at 2x times that of DRAM memory frequency - so at 2:1 uncore to memory frequency ratio. If you set your uncore higher than 2x memory frequency you will need way more QPI/DRAM (uncore) and VDIMM memory voltage to get stable (see tests).

    • Example, say you have 6x2GB @1333mhz working fine at 1.35v QPI/DRAM with 1.65v VDIMM. You try to overclock the memory to @1600mhz speeds, and you bump VDIMM from 1.65v to 1.75v and now only see 8-10GB detected. You've moved out of the optimal differential range for QPI/DRAM to VDIMM which @1333mhz was 1.65 - 1.35v = 0.3v. At 1.75v VDIMM you left QPI/DRAM at 1.35v so 0.4v differential voltage. Then you bump QPI/DRAM to 1.45v to keep 0.3v differential voltage and 12GB is detected again. Now this is just an example, it could be you need 1.85v VDIMM for your memory to be stable and if 0.3v is optimal differential voltage it means you need QPI/DRAM set at 1.55v
  3. Setting some important voltage settings to AUTO instead of lowest manual available voltage option. See 2nd post here for suggestions.
  4. faulty memory modules
  5. faulty memory dimm slots
  6. sort of combination of 4+5 above where memory modules like particular memory dimm slots - could come down to PCB differences for each module along with voltages for QPI/DRAM and VDIMM.
  7. If you see full memory size in DOS/memtest but not within windows, then it could be due to 32bit/64bit memory addressing size being chewed up by video card and pci/pci-e devices as explained at and So if you have 6GB installed, but have 1GB video card on 32bit OS you may only see between 2.25-3GB of memory available in windows. On 64bit OS, you may only see 3.5-4.5GB memory available. If you add other PCI-E devices like sound cards, then that also further eats into available windows memory. Windows 7 users: read
  8. Update: Added another possible reason, too tight tension in mounting cpu cooler to motherboard. Improper contact of cpu pads with socket might also result in less memory detected. So especially for water cooling folks to try loosening the screws and tension a tad for cpu mount. You can try removing cpu from socket as well and reinstalling/remounting cpu cooler and see if that helps.
  9. Update: Apparently short circuiting the motherboard can cause memory detection errors as well i.e. check cpu cooler's back plates and if they short any part of the backside of the motherboard. Example here and here.
  10. Update: For Core i7 980X Gulftown owners, the uncore to mem frequency ratio requirements changed from 2x ratio to allowing 1.5x ratio, but 1.5x and 2.0+ ratios may need more CPU VTT and VDIMM than normal, thus safe uncore ratios usually between 1.66x and 1.84x for slightly lower CPU VTT and VDIMM usage. So for 12x mem multi might try between 22-23x uncore multi instead of 24x. For 14x mem multi might try 26-27x uncore multi instead of 28x uncore multi. For 8x mem multi might try 15x uncore multi instead of 16x uncore multi. All just practical experience with my Core i7 980X - full details here.

  1. Also don't count out needing to tweak, IOH, IOH/ICH PCI-E, ICH voltages as well as DRAM DATA/CTRL REF voltage tweaks for each memory Channel A/B/C
  2. When testing full memory dimm slot populated configurations (6x2GB) or any configs, it's also worth testing each memory module (label them with masking tape from #1 to #6 etc) in each of the 6 dimm slots, jot down notes as to how each module performs in each of the 6 dimm slots, then pair them up with best matching of memory modules for dimm slots. Reason is triple channel kits while sold to you as matched, they are rarely really matched in terms of overclocking characteristics - you'll always have a module or two which either does better or worse than the average of the 3 modules. Now take that to 6 modules and you can see why sometimes it might not work that well.
  3. It's also worth testing each module (labeled #1 to #3 or #6), rotating them in the dimm slots. If the same module doesn't get detected in cpuz spd tab (drop down menu to access other dimm slot inserted module info) and in bios RTL channel A/B/C (one channel reports RTL = 0 - so if RTL channel B = 0) that means module in dimm slots 3 or 4 is the problem module. On other hand if same dimm slot has issues regardless of module used in that slot, then could be dimm slot/board. Of course these symptoms don't rule out other reasons as listed above

Further Recommended Reading & Examples:



Update: Started playing with 6x2GB A-Data 2000X configuration on Asus P6T6 WS Revolution and not all 2GB modules behave the same so 6x2GB is much more trickier due to using 3x 4GB dual channel kits and my above guide and process does play out in testing for 6x2GB stability - meaning break down testing to individual 2GB modules, then retesting in 3x2GB and 6x2GB configs

12GB A-Data 2000X to 8x32M Pi stable @DDR3-2000Mhz 8-9-8-25 2T at 1.62v vdimm with 1.50 QPI/DRAM uncore voltage with max validation at same voltages @DDR3-2112Mhz 8-9-8-25 2T!

12GB - 6x2GB A-Data 2000X
@DDR3-2000Mhz 8-9-8-25 2T at 1.62v
(Kit 1 + 2: module #1 + #2 + #4 + #3 + #5 + #6)

tRFC = 110
tFAW = 38
B2B = 4

HyperPi v0.99b - 8x32M Pi

Single Super Pi 32M

Everest Bandwidth

12GB - 6x2GB A-Data 2000X
@DDR3-2112Mhz 8-9-8-25 2T at 1.62v
(Kit 1 + 2: module #1 + #2 + #4 + #3 + #5 + #6)

Last edited by eva2000; 09-12-2010 at 05:49 PM.
eva2000 is offline   Reply With Quote