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I never got an answer in my googling to this about a year ago and have an extra stick of memory I'd like to be able to use. When is inserted the computer starts, and then reboots immediately in an endless reboot cycle. As soon as the 4th stick is removed, the computer works fine. Right now I have 6 GB of my 8 GB installed.

Is there a solution that I am missing to enabling this motherboard to actually boot up with all 8 GB (it supports it). Right now it won't even boot up to BIOS with the 4 sticks... only 3?


Memory: 1 x G.SKILL 4 GB (2 x 2 GB) 240-Pin DDR2 SDRAM DDR2 1100 (PC2 8800) Dual Channel Kit Desktop Memory Model F2-8800CL5D-4GBPI - Retail
(URL: ) http://www.newegg.com/Product/Product.aspx?Item=N82E16820231194

Motherboard: 1 x GIGABYTE GA-EP45-UD3R LGA 775 Intel P45 ATX Intel Motherboard - Retail ( URL: )http://www.newegg.com/Product/Product.aspx?Item=N82E16813128359


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Does it matter which 3 of the 4 sticks are used? Might also be lacking power -- have you tried disconecting all other devices (drives, etc) and test for boot? –  techie007 Mar 9 '10 at 18:04
    
1) no, any sticks, also did memtest, and they are all fine. its the 4th stick being added. 2) All devices disconnected, still does this... EVEN WITH CPU not in. I built this system, so tested from scratch when this issue occured. Returned motherboard 2 times thinking it was a motherboard problem. –  g00p3k Mar 9 '10 at 18:38
    
If the CPU is not in, then the machine won't boot anyways. –  LM. Apr 30 '10 at 19:58
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2 Answers

up vote 2 down vote accepted

The dirty little secret of most modern motherboards is that they rarely support more than two sticks of memory (or three for tri channel i7) at the highest speeds, lowest latency, and dual or tri channel. If you have any of these BIOS settings locked, you could find your system unstable. Many people do not notice the silent loss of dual channel when going from two to four sticks because the BIOS gives no visible clue, the speed difference is just a few percent, and there are other benefits from larger memory, such as better disk caching and better multitasking task switching.

Insufficient or unstable power, as techie007 mentioned, is another probable cause.

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great! i have a great power supply, but you are talking about the voltage to the memory? By lowering the voltage/speed of the ram, i should benefit from higher memory and not notice the slight speed different right? –  g00p3k Mar 9 '10 at 18:34
    
Voltage and speed in MHz may do it, but also consider the CAS latency and other timings. These may have to be lower than what the SPD specifies in order to work in sets of four. I would leave RAM at standard speed such as 1066MHz or 800MHz, if you can't get into the BIOS you may have to go back to two sticks temporarily, and use BIOS defaults for everything. Then try four sticks, if that works, you can start overclocking towards the 1100MHz rating until it breaks, then back off. –  kmarsh Mar 10 '10 at 13:07
    
i'm selecting this as the answer, though it was tough between both of you guys, thanks for the help –  g00p3k Jul 20 '10 at 22:56
    
Thanks for accepting my answer! –  kmarsh Jul 21 '10 at 17:00
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Well, according to the specification sheet that board should support up to 16 GB of memory, so I don't think that is the issue.

I have seen problems like this where the memory just wasn't happy with all the slots populated as the required load is much higher and the system becomes incredibly picky about accepting memory. Typically boards are only qualified for a full complement of RAM with very specific modules.

One thing you can try though: Go into the BIOS and force your memory down to 800 or even 667 MHz instead of running at the higher speed. This may help give it the stability it needs. You can also try tweaking the voltage up, as that may also have a positive impact.

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great points, would this noticeably affect the memory's speed? Additionally, this might cause issues if I look at overclocking right? –  g00p3k Mar 9 '10 at 17:15
    
Overclocking is probably out of the question with four sticks, and certainly VERY limited if you actually do accomplish it. As for performance, you could probably measure a performance drop in memory intensive operations, but in daily use it will likely not be noticed. –  Goyuix Mar 10 '10 at 14:35
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