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Prime95 blend test failing immediately

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November 20, 2011 9:18:04 PM

I've been trying to figure out how to overclock my system for a little while now. Every time I thought I had done it, I would end up getting the BSoD. I was starting to think this was a memory problem because the default speed was 1333 in the BIOS when it should be rated at 1600. I recently found an option in my bios that let me set an XMP profile or something and it automatically overclocked my cpu while setting my ram to 1600. However, I'm still getting the BSoD and when I run prime95 blend test it immediately fails on all cores. Here are my parts:

PSU: Corsair TX650W
Mobo: Gigabyte EP43T-UD3l mobo
RAM: ADATA XPG Gaming Series DDR3 1600 (PC3 12800)
CPU: Intel® Core™2 Quad Processor Q9550

A couple other problems I've been having is the cvore setting. If I leave it on auto it idles at 1.36v which is pretty much the limit and while running prime95 it drops down to 1.31v. If I try to change the vcore manually it seems to lower significantly and sits around 1.26v at idle and 1.22v when running prime95 no matter what I set the vcore to. Also, my ram's voltage is recommended to be 1.65v. I have it set to 1.66v because it doesn't do odd numbers. Sorry, I am a complete noob with this stuff and I just can't seem to figure out what's wrong with my pc. I'm going to try to find a friend with extra ram so I can see if mine is bad or something.
November 20, 2011 10:38:40 PM

I would run Memtest86+ on your system, 1 dimm at a time to make sure the memory isn't faulty
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a c 197 K Overclocking
November 21, 2011 9:18:26 PM

Can't hurt, but the memory is probably OK.

Your 1600 memory is running at a default of 1333 MHz because it is 1333 MHz memory.

1333 is default because that is the value programmed into the SPD chip on each memory stick.
http://en.wikipedia.org/wiki/DIMM#SPD_EPROM

Then after it came off the production line, the memory was tested to see if it would run at 1600 MHz.

So, first, take your memory off the XMP profile.

Next, read these two guides:
Core2 Overclocking Guide (generic guide based on an Asus motherboard)
http://www.tomshardware.co.uk/forum/259899-11-core-over...

Shadow's Gigabyte motherboard OC guide:
http://www.tomshardware.co.uk/forum/page-245679_11_0.ht...
It's for an EP35-DS3L but all the Gigabyte Core2 BIOS's are similar.

This guide is designed for a motherboard using DDR2 RAM, so we need to change that.

Go into the BIOS M.I.T. section and change the System Memory Multiplier from Auto to 4.0. That will set the FSB:RAM ratio to 1:1.

Now you can start the "increase FSB, test OC and monitor temps, increase CPU core voltage if needed, retest" cycle.

Keep your core voltage under 1.45 volts and your load temps under 70 C.
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November 22, 2011 1:07:18 AM

jsc said:
Can't hurt, but the memory is probably OK.

Your 1600 memory is running at a default of 1333 MHz because it is 1333 MHz memory.

1333 is default because that is the value programmed into the SPD chip on each memory stick.
http://en.wikipedia.org/wiki/DIMM#SPD_EPROM

Then after it came off the production line, the memory was tested to see if it would run at 1600 MHz.

So, first, take your memory off the XMP profile.

Next, read these two guides:
Core2 Overclocking Guide (generic guide based on an Asus motherboard)
http://www.tomshardware.co.uk/forum/259899-11-core-over...

Shadow's Gigabyte motherboard OC guide:
http://www.tomshardware.co.uk/forum/page-245679_11_0.ht...
It's for an EP35-DS3L but all the Gigabyte Core2 BIOS's are similar.

This guide is designed for a motherboard using DDR2 RAM, so we need to change that.

Go into the BIOS M.I.T. section and change the System Memory Multiplier from Auto to 4.0. That will set the FSB:RAM ratio to 1:1.

Now you can start the "increase FSB, test OC and monitor temps, increase CPU core voltage if needed, retest" cycle.

Keep your core voltage under 1.45 volts and your load temps under 70 C.


Thank you for the links. Fortunately I've read the Core2 OC guide but I didn't see the gigabyte mobo OC guide. The System Memory Multiplier has 3 different options I can select, 4.00A, 4.00C and 4.00D. Each of these settings do not change my FSB:RAM from 1:2 to 1:1 according to CPUID. In fact, it seems like my ram doesn't like it when my FSB is anything but 333.
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November 22, 2011 2:22:43 AM

Best answer selected by penguinswithpie.
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November 22, 2011 2:24:32 AM

I may have spoken prematurely. The first time I was able to get my PC to post running at 3.4Ghz the blend test failed after only a minute. I decided to just leave my PC and run a CPU intensive game to test it out, and it wasn't crashing so I ran the blend test again. So far so good, I think you may have just stabilized my PC. I owe you one, JSC.
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November 22, 2011 4:40:11 AM

Once again, I spoke to soon. My good fortune was only a fluke, it seems. I decided to restart my pc earlier and it refused to post. I can only seldom get it to post after changing the SMM to anything, and if it does then the prime95 blend test fails immediately. I'm just not meant to OC this PC. Thank you for your help.
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a c 197 K Overclocking
November 22, 2011 2:29:48 PM

Your not quite done yet. If your RAM is running at 1.5 volts (default for DDR3) try raising it up to 1.65 volts. That is max recommended voltage for DDR3 RAM. There is no danger to your CPU because the Q9550 uses an external memory controller.
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November 22, 2011 7:17:13 PM

I have it set to 1.66v because the recommended voltage for my RAM is 1.65v. Should I set it down to 1.64v? It only does even numbers.
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