Won't boot unless 3N

[Silex99]

I just added 2 X 2GB of the same exact Corsair 7-8-7-20 DDR3 1600mhz 1.65 volt to my Asus P7P55D EVO for a total of 8GB using all 4 slots. After spend hours on dozens of configurations and updating the bios to the latest January revision, the only way I could get it to boot was by setting the ram to 3N.

I tried the standard XMP setting. I tried running it at stock settings with ram set to 9-9-9-24 1333mhz. I even tried under clocking the CPU and ram.

A little background may be helpful. I had quite a bit of trouble getting the original 2 sticks running when I built the machine. I eventually got it running at 3.4ghz (21.0 X BLK 160) 1600mhz 1.65v and set the cpu to 1.15v. But it never ran correctly by simply setting the auto (default XMP settings.) I ended up doing a great deal of research and found that it ran better at the manual over clocked settings. It was running stable at those settings for 5 months. Memtest CD even passed on a 20 hour run. Funny thing is the machine was always unstable on a cold boot. Every cold boot I would have to boot into the bios, change nothing, exit saving changes and everything was fine again.

Anyway, I need to know what I am losing with the 3N setting. From what I have researched the machine should run perfectly on the 2N/2T setting. Is there something else I could try to get the machine running with 2N? Should I increase voltage somewhere? The BIOS already makes the 1.65V RED even though that is what the box says it should be. I can run the system at my old overclock with the 3T setting but I will admit it seems slower but it could be my imagination. Any help would be appreciated.

FYI it may not matter but running 2 GTX460s in SLI and running RAID 0. I have a massive cooler too - it's not getting hot.

 

[Leaps-from-Shadows]

The 1.65v setting is red because you shouldn't go above that with a Nehalem-based CPU or it could damage the CPU itself.

What the board probably needs is a little bit of extra voltage to run all four sticks of RAM. The problem is, you can't do that or you risk damage.

Is there a CPUIO or VTT setting for voltage in your BIOS? If so, what's it set at?

 

[Silex99]

Ok. Actually the Ram voltage is purple. The manual says that the text will not read red until 1.7V. There is a switch on the MB to allow voltage above 2V. Would it be ok to play with voltages between 1.65 and 1.7?

As far as your question about CPUIO or VTT here are the other things I see in the bios. There is an "Intel VT-d" set to disabled in the advanced CPU menu. Back in the other menu for overclocking I see QPI set to auto. IMC is set to auto and averages 1.21V. CPU PLL is set to auto and averages 1.81V. PHC is set to auto and averages 1.05V. DRAM DATA REF CHA/B is auto. Load Line Cal. is auto. CPU Spead Spectrum is auto. PCI Spread is auto.

Again I ask, is 3N/T a big performance hit. Should I avoid this setting at all costs? Thanks again.

 

[Leaps-from-Shadows]

Would it be okay to play with voltages between 1.65 and 1.7? If you want to fry your CPU, yes. If you want your CPU to last a while, then no. There's a post on these forums today where it looks like someone fried their CPU by running their RAM at 1.65v and Intel won't honor their warranty because they said 1.65v is out of specification.

I guess your board calls it IMC (CPUIO=VTT=IMC, all names for the same thing).

Running the Command Rate at 3T/3N will be slightly slower. Will you be able to notice? Probably not, as the difference is only a few percentage points.

 

[Silex99]

You said "What the board probably needs is a little bit of extra voltage to run all four sticks of RAM." I take it you were saying I may want to increase my IMC voltage? Currently the auto sets it at 1.2V. Can I (somewhat) safely increase this number any?

 

[Leaps-from-Shadows]

No, I was referring to what you can't raise: DRAM Voltage.

The IMC voltage is already high enough -- 1.2v is higher than default, I think.

 

[Silex99]

I have determined that my original ram is defective:

I had quite a bit of trouble getting the original 2 sticks running when I built the machine. I eventually got it running at 3.4ghz (21.0 X BLK 160) 1600mhz 1.65v and set the cpu to 1.15v. But it never ran correctly by simply setting the auto (default XMP settings.) I ended up doing a great deal of research and found that it ran better at the manual over clocked settings. It was running stable at those settings for 5 months. Memtest CD even passed on a 20 hour run. Funny thing is the machine was always unstable on a cold boot. Every cold boot I would have to boot into the bios, change nothing, exit saving changes and everything was fine again.

The new ram, when used by itself, experience none of these symptoms. I reset the bios, set the XMP setting and it works like a charm. That NEVER worked with the original ram. I even popped the old ram in under these settings again to be sure and the machine crashed again right after logging in. I have built 7 PCs and never had so much trouble getting ram to work as I did with this ram. I should have known better. It's apparent that my over clock must have added enough juice to hide the defect. Thank *** for lifetime warranties on memory. I have my RMA and should be all set in a week! Thanks for your help Leaps-from-Shadows.