P31 Neo-F - I don't have 1:1 FSB\memory ratio

Question

MSI P31 Neo-F (Bios 1.2) Rev 1.0
Corsair 6400XMS2 2 x 1Gb (Dimm1 & Dimm3)
Core2Duo 4300
Core2Duo 6300
The BIOS sees both sticks of RAM. I have tried slots 2 & 4 in desperation as well.
I can not get 1:1 memory ratio.
With the 4300 I get AUTO\1:1.66\1:2. Set to Auto it runs at 1:1.6
With the 6300 I get AUTO\1:1.25\1:1.5 (if my memory servers me right). Set to Auto it runs at 1:1.25
I have cleared the BIOS many times. What am I doing wrong?

Answer 1

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The Corsair memory is DDR2-800 isn't it?
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Corsair 6400XMS2 2 x 1Gb (Dimm1 & Dimm3)
Yes, and there should be no problem making your RAM operate @800 Mhz by choosing the proper FSB/DRAM ratio in BIOS.
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My MSI P35 Plat runs with the same memory at 1:1 fine with the same processor. So are you saying the P31 can not do the same?
I know, this matter is complicated, but I will try to explain and to give you at least a partial answer.  P31 and P35 chipsets do not use the same memory controllers.  Have a look at the Intel Datasheets for both memory controllers:
P31 / 82P31 Memory Controller Hub (MCH)  --> DATASHEET
Page 21:
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Supports Front Side Bus (FSB) at the following Frequency Ranges: - 800/1066 (200/266MHz)
and Page 25:
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Differential Host clock of 200/266 MHz (HCLKP/HCLKN). Supports transfer rates of
800/1066 MT/s.
Compare to:
P35 / 82P35 Memory Controller Hub (MCH)  --> DATASHEET
Page 27:
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Supports Front Side Bus (FSB) at 800/1066/1333 MT/s (200/266/333 MHz)
and Page 31:
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Differential Host clock of 200/266/333 MHz (HCLKP/HCLKN). Supports transfer
rates of 800/1066/1333 MT/s.
As you can see, according to Intel specs, the P31 chipset itseld does not offer native support for CPUs that operate @333 (1333) MHz FSB Clock Speed.  That is why, from a chipset point of view, the number and variety of possible dividers is less compared to the P35 chipset.  Looking at the differential between FSB and Memory Clock speed you can also see that 1:1.25/1.1.5 (E4300) and 1:1.66/1:2 (E6300) are the native chipset ratios to match DDR2-667 and DDR2-800 RAM with FSB/200 MHz and FSB/266 MHz processors.
Of course, in practice chipset limitations can be exceeded by BIOS programming to a certain degree. That is why P31 boards actually do support FSB/333 MHz CPUs, but the support is not native. Have a look >>here<< as well.
The only situation in which you actually need the 1:1 memory divider is overclocking, but since this a budget board not meant to be put to excessive OC use, BIOS implementation of memory dividers that go beyond Intel specs is limited. After all, it is a matter of price/performance.  The MSI P31 Neo-F matches the Intel specs and exceeds them when it comes to FSB/333 MHz processors, there is no real mistake here. I can find nothing in the Intel specs nor in the MSI Product information that says there has to be a 1:1 ratio implemented at all costs.
There is a chance, of course, that MSI will implement more memory dividers in a future BIOS release.  Try contacting MSI, maybe they can give you a more definate answer this one:
http://ocss.msi.com.tw/
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The Intel chipset is capable of offering 1:1
Capable: yes, native support: no.
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The issue is MSIs implementation of it = BIOS.
You are most likely right about BIOS implementation in general, but I don't see a reason to call it an issue at this point.