@noInk are you referring to Host Clock Frequency Multiplier?

@eivrah

Yes, the base clock on intel user menu is named Host Clock Frequency Multiplier.
Mine can't reach 142 no matter what ( just tried an i920 pretty much the same )
The PLL cannot be manually set ( it's defaulted @ 1.5 ) also, the memory setting on the x5670 goes all over the place and doesn't get read correctly by the bios if the user save a know to be working value (this doesn't happen with the i920).
Forgot to tell you, the bios you got doesn't provide i920 support.

@noInk I'm on 150 Right now haven't touch yet 160 barrier since my other cooler is on my other PC.

@eivrah

Might be just this x5670 then or the board revision.
I'll try one x5675 next week.

@noInk I'll send you update later when I get home. I have doubt if this board will support ECC PC3-10600R RAM. It will be good if it will. I have known someone who have the same processor as your x5670.

Update: I asked him again and said his processor could not boot past 3.2Ghz

@eivrah

Yea, I have no idea.
With this board revision nothing boot if I change just by a little the host clock frequency.
Could be the i920 and x5670 too high voltage requirement incompatibility later fixed in the i950 and x5675, dunno.
Gotta try when the x5675 arrive, I ordered one.

@noInk could be the processor or the board, my i7-950 could boot past 160 multiplier not sure with the xeon though.

It's the board revision somehow it doesn't allow any "Host Clock Frequency" changes.
The X5675 has the same issue as the x5670 and i7920.
I'm stuck with default 133-135MHZ.

@noInk Here's mine.

I've also thought about but it's happening with all of these (know to work on other system) memory kit's:

HyperX HX318C10FWK2
HyperX HX316C10FWK2
Crucial BLE8G3D21BCE1
Corsair CMZ12GX3M3A1600C9

I've also tried some proliant dismissed HP ECC memory, no avail.

I'm just using the 8PIN CPU and full 24 ATX cable are you using anything else like the optional PCI-EX molex-or-sata cable? does your board has those?
What happen if you set manually the memory multiplier to 10 and the uncore to 20? does it boot?
and what if you set the memory multiplier to "auto" and the uncore multiplier to 20 and then select the "Manual - User Defined" and hit enter? does the uncore move to 9?

I think mine board is ignoring the applied settings and the MEM/QPI ratio fix implemented by intel goes somewhow out of bound because the user menu variable doesn't allow the uncore to move to 9..

0x2F6F Numeric: Uncore Multiplier (30-12), Variable: 0x238[1] {07 14 38 02 01 FE 00 C0 04 10 00 00 0C 00 1E 00 01 00 14 00}
 
 

Anyway, with the x5675 I leave just as that for a while cause I have no clue.

@noInk I have my memory multiplier is set to 10 by default and I have no 9 in the multiplier only 8. Also my RAM timings are a bit different. Are you using 1600 mhz RAM's?

Yea, these are 1600|1800|2133 memory I'm testing.

@noInk I only have 1333mhz RAM's here though I'm planning to buy 1600 maybe next month, but I think the board limits to 1333 so need to overclock.

Tried to leave the memory untouched by rewriting by hand some user menu entry.
Moved the QPI setting from the Memory Configuration form to the QPI Configuration, Bus Overrides entry and it's the same.
Can't change the Host Clock Frequency Multiplier without making the board unbootable.

@noInk can you upload your modded BIOS? I'll try it with mine.