bios doesn't see pc-6400

Asus M2n68-la motherboard
January 26, 2010 at 10:35:53
Specs: Windows 7
upgrade hp pavilion m9100z to windows 7 and 8gb ddr2-800 (pc-6400) ram. Bios only reads it as pc-5300. If I reduce it to 4gb, it sees it at pc-6400.

My question is what arrangement gives me better performance?

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January 26, 2010 at 22:12:45
Your problem is u mixed ram speed. Let say u have (4x2gb) and one stick of 2gb is ddr2 667(pc2 5300) and the rest is ddr2 800 what happens if u install both memory, all memory will run at the same speed (ddr2 667).When u remove 2 sticks and remain with 2x2gb the memory run at ddr2 800 why? Bcause u remove ddr2 667.What is your cpu name?If u have intel cpu based on c2d u need to maintain ratio 1:1 fsb:dram for eg c2d e8400 fsb 1333/4=333.25 and ddr2 667/2=333.5 that ratio 1:1 ram speed must match with cpu speed. If u have athlon x2 or II X2 works well with ddr2 800, phenoms works well with ddr2 1066.

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January 27, 2010 at 01:49:06
Yes, basically what kuwese is saying is that not all your ram modules are the same speed. If you configure the pc to use all the ram, it can only run at the slowest of those two speeds.

But when you configure it to use only 4gb ram, those modules with the slower speed are ignored - so the ram can now operate at the higher speed.

To answer your question about which configuration gives the better performance, I personally would prefer to use all the ram even if it runs slower than using only half of it. There's a vast difference between 4 and 8 GB.

Moreover, what's the point of having 64-bit Windows if you're not going to take advantage of it's ability to address more than 4 GB ram when you've paid for the extra modules?

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January 27, 2010 at 02:52:31
"i personally would prefer to use all the ram even if it runs slower than using only half of it"

i don't agree, it depends on cpu fsb. Cpu Fsb 1333, ram (4x2gb) 2sticks(2x2gb) run at 533 and other 2 sticks run at 667, if u put all ram sticks, all memory will run at 533 which is wrong. If u wanna gain performance u need to remove 2 sticks ddr2 533 and leave 2 sticks ddr2 667 as i explained u need to match cpu external speed and ram speed. And for athlons x2 works well with ddr2 800, if u have athlon II X2 cpu u need to remove ram with 667 to gain perfomance. Between 4gb and 8gb there's no difference or if there is difference (so small).

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January 27, 2010 at 06:09:33
First of all you didn't specify if your Windows 7 is 32 bit or 64 bit. All 32 bit operating systems can only configure 4GB of RAM and will run with something less than that after allocating for hardware.

I suspect the memory controller/s is the reason for the stepping down of the RAM speed. I am assuming you know what RAM you do have.

To verify this, go to and run their online scanner. It should report how much and what kind of RAM your board is capable of supporting.

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January 27, 2010 at 07:56:55
My 8gb or ram for (for Windows 7 64-bit OS)are as follows:

4gb gskill f2-6400cl5d-4gbpq and 4gb crucial ct25664aa800 - both of these are specified as pc-6400.

The gskill is CL5 while the crucial is CL6.

My CPU is an AMD Phenom 9500 quad-core - 2.2GHz
Motherboard is hp's narra3 (asus m2n68-la)
Maximum Memory Capacity: 8192MB
Currently Installed Memory: 8GB
Available Memory Slots: 0
Total Memory Slots: 4
Dual Channel Support: Yes
CPU Manufacturer: AuthenticAMD
CPU Family: AMD Phenom(tm) 9500 Quad-Core Processor Model 2, Stepping 2
CPU Speed: 2200 MHz

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January 27, 2010 at 09:36:47
The downclocking of the RAM speed *may* have something to do with the limitations of the Phenom's integrated memory controller. Interestingly enough, there's very little performance difference between DDR2-533 & DDR2-1066.

BTW, the 9500 is one of the early model "broken" Phenoms with the TLB bug.

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