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Asus Motherboard memory problem

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December 3, 2009 5:32:41 PM

The mother board that I am going to purchase with an Intel Core i7-860 Lynnfield 2.8GHz 8MB L3 Cache LGA 1156 95W Quad-Core Processor is an ASUS P7P55D PRO LGA 1156 Intel P55 ATX Intel Motherboard.

I was suggested by others on this form to purchase G.SKILL Ripjaws Series 4GB memory. 2X 2GB. I am going to purchase 2 so I will have 8GB in total.
The problem is that when I went on the ASUS website and checked the Qualified Vendor List (QVL) to see if this memory was compatible it was not on the list. I do not think that matters, but what I did not understand was this:
Quote:
You may install varying memory sizes in Channel A and Channel B. The system maps the total size of the lower-sized channel for the dual-channel configuration. Any excess memory from the higher-sized channel is then mapped for single-channel operation.
• Due to Intel spec definition, X.M.P. DIMMs and DDR3-1600 are supported for one DIMM per channel only.
• According to Intel CPU spec, DIMM voltage below 1.65V is recommended to protect the CPU.
• According to Intel CPU spec, CPUs with a core frequency of 2.66G support the maximum DIMM frequency of up to DDR3-1333. To use DIMMs of a higher frequency with a 2.66G CPU, enable the DRAM O.C. Profile feature in BIOS.
• Always install DIMMs with the same CAS latency. For optimum compatibility, we recommend that you obtain memory modules from the same vendor.
Due to the memory address limitation on 32-bit Windows OS, when you install 4GB or more memory on the motherboard, the actual usable memory for the OS can be about 3GB or less. For effective use of memory, we recommend that you do any of the following:
- Use a maximum of 3GB system memory if you are using a 32-bit Windows OS.
- Install a 64-bit Windows OS when you want to install 4GB or more on the motherboard.
For more details, refer to the Microsoft® support site at
http://support.microsoft.com/kb/929605/en-us.
• This motherboard does not support DIMMs made up of 512Mb (64MB) chips or less (Memory chip capacity counts in Megabit, 8 Megabit/Mb = 1 Megabyte/MB).



Why is it that only 3GB of memory can be used?
If I install Windows 7 Professional 64bit will I have all 8GB of my memory?
December 3, 2009 5:41:30 PM

32bit O.S are restricted to use up to 3.5GB of RAM due to its data fetching architecture.
In Windows7 32bit it'll show 4GB RAM if installed, but could only utilize 3.5GB.

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December 3, 2009 7:25:29 PM

To answer your question, yes, if you install 64-bit Windows 7 (or any 64-bit OS, for that matter), you'll be able to use the full 8GB of RAM.

Which version of the Ripjaws memory are you planning on buying? Check the voltage first. I would not get one of the 1.6V versions because it's not recommended to use more than 1.65V with an i7 chip. Normally you'd be fine, but if you fill all four DIMM slots, the memory often requires more juice. Usually not more than an extra 0.1V, but you don't leave yourself much breathing room with RAM that is 1.6V to begin with. So if I were buying it, I'd make sure to get RAM that was 1.5V or 1.35V just to avoid any potential headaches.
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