Instabilities: Gigabyte GA-P55A-UD3 w/ 4 DIMMs (12GB)

[jbug187]

Hello, I'm having some trouble getting my machine to run stable. I have a suspicion that it has something to do with the different pairs of DIMMs that I have in my machine, but I?m not sure. I am using 2 x 2GB (F3-12800CL9D-4GBRL) sticks and 2 x 4GB (F3-12800CL9D-8GBRL) for a total of 12GB. These sticks are using all four of the DIMM slots on my motherboard. Note that while the capacity of the memory sticks is different, the type (DDR3), speed (1,600MHz ? PC3-12800), latency (CL9-9-9-24), and voltage (1.5v) are all the same.

The machine boots to Windows and recognizes all 12GB without a problem and it hasn?t blue screened at all. All temperatures are fine, even under load, and it was able to pass the Prime95 small lff test every time I?ve run it. However, I was still failing tests under memtest v4.1 and Prime95?s large lff test after about two minutes of the tests running. After doing a bunch of ?research? on forums like this I changed the tRCD setting on both channels from 9 to 11. This seems to have helped because it now takes twice as long (~4 minutes) for the machine to fail the Prime95 large lff test and the memtest. Also, if I lower the SPD multiplier to 6x, and have the memory running at 1,200MHz I can pass all tests without issue.

My current settings are listed below. I?m running out of things to try here, but very much want to get things stable at 1,600MHz. Can someone please give me some advice on what I can do to get stable while keeping the memory at its rated speed of 1,600MHz? What else can I adjust besides the tRCD to help here? Any reason why everything would work fine at 1,200MHz and then fail tests at 1,600MHz? Thanks in advance for your help.

COMPONENTS
Motherboard -- Gigabyte GA-P55A-UD3
CPU -- Intel Core i5 760
CPU Cooler -- Hyper 212 Plus
Memory -- G Skill DDR3-1600 PC3-12800 CL9-9-9-24 1.5v (2x2GB and 2x4GB)
PSU -- Cooler Master Silent Pro M 600W
Case -- Cooler Master HAF 912

MOTHERBOARD SETTINGS
CPU Clock Ratio (x) -- 20
BCLK Frequency (MHz) -- 200
CPU Frequency (GHz) -- 4,000
QPI Clock Ratio (x) -- 32
System Memory Multiplier (SPD) -- 8.0
Memory Frequency (MHz) -- 1,600
Intel Turbo Boost -- disabled
CPU Enhanced Halt (C1E) -- disabled
C3/C6 State Support -- disabled
CPU EIST Function -- disabled
Bi-Directional PROCHOT -- auto
Extreme Memory Profile (XMP) -- disabled
System Memory Multiplier (SPD) -- 8.0
Performance Enhance -- standard
DRAM Timing Selectable -- expert
CAS Latency Time -- 9
tRCD -- 11
tRP -- 9
tRAS -- 24
Load Line Calibration -- enabled
CPU vCore -- auto
QPI / Vtt Voltage -- auto
CPU PLL -- auto
DRAM Voltage -- auto

[Leaps-from-Shadows]

When you use all RAM slots, most boards will require that you bump the RAM voltage up a bit. Try the advertised timings (9-9-9-24) at 1.55v or 1.6v and you should see stability improve quite a bit (hopefully to rock-solid).

Also, you should have the RAM arranged like this:
Slot 1 2GB
Slot 2 4GB
Slot 3 2GB
Slot 4 4GB

[Tradesman]

Will prob have to raise QPI/VTT voltage as well as vCore...and may have to play with base timings

[jbug187]

Thanks for the replies, guys. I'll try setting voltages manually and moving them up slowly to see what I get. Since I've seen some improvement in stability when adjusting the memory timings, I'd like to start fiddling with that as well. Any guidance on where to start adjusting, and what acceptable ranges are for my 9-9-9-24 memory? Thanks.

[Tradesman]

@ 1600, will prob want to stick to the factory specs, if you downclock to 1333 you can tighten the timing to CL8, say 8-8-8-24 which should perform close to 1600 @ CL9

[jbug187]

I understand that the memory timings can be different depending on what speed you have the memory running at (1,200MHz versus 1.600MHz). My BIOS has a number of settings that I can change for the timings, and while I have the basic 9-9-9-24 configured, I'd like to hard code the correct settings for the other values so that I know they are in there correctly, and I can eliminate the BIOS as a potential part of the problem (when it decides what the 'auto' setting should be). I looked at the product pages on the G Skill web site, and there was no documentation that came with the memory I bought from NewEgg (in retail packing). Do you guys have the correct values for the different timings that I currently have set to 'auto' in the list below? I know these can change depending on what speed the memory is running at and I'm trying to run it at the rated speed of 1,600MHz. Thankz!!!1

CAS Latency Time -- 9
tRCD -- 9
tRP -- 9
tRAS -- 24
tRC -- auto
tRRD -- auto
tWTR -- auto
tWR -- auto
tWTP -- auto
tWL -- auto
tRFC -- auto
tRTP -- auto
tFAW -- auto
Command Rate -- auto
B2B CAS Delay -- auto
Round Trip Latency -- auto

[GSKILL TECH]

Take a look at AUTO settings, then input those and experiment if you want to input advanced timings. Otherwise AUTO is sufficient.

Make sure to input basic memory settings, reboot, then go back into BIOS for advanced timings. They need to change according to the basic settings first, otherwise it will show you DDR3-1333 CL9 timings.

Thank you
GSKILL TECH