Core i7 multiplier changing on the fly

[kyosen]

I'm playing with Nehalem/Core i7 recently, and noticed the MSR register
for determining the multiplier of each core on CPU-Z's Regsiters Dump.
I changed the register values with MSR Editor of CrystalCPUID, and
suceeded in changing multiplier on the fly

In Intel DX58SO, 1-CORE~4-CORE on the BIOS are corresponding to
Core#0～Core#3 on CPU-Z, and MSR 0x000001AD determines each multiplier:
EAX(31-24) for 4-CORE/Core#3
EAX(23-16) for 3-CORE/Core#2
EAX(15- 8) for 2-CORE/Core#1
EAX( 7- 0) for 1-CORE/Core#0
and the formula of register value:
19 = x25
1A = x26
1B = x27
1C = x28
1D = x29
1E = x30
1F = x31
20 = x32
21 = x33
22 = x34
23 = x35
24 = x36

I also observed *.5 multiplier running, but couldn't find which register
determining it so far...

Several screenshots are here:
http://www.oohashi.jp/c-board/c-boar...ne;no=5464;id=

BTW, Intel DX58SO's over x30 multiplier problem has been fixed
with BIOS 2747, finally
http://www.oohashi.jp/c-board/c-boar...ne;no=5471;id=

Enjoy it at your own risk!!!

[Charles Wirth]

Good info, thanks Kyosen-san

Would love to see you guys work on the uclk, huge gains there.

Pi times will get real interesting with increased efficiency.

[GLENBOY]

good info as usual kyosen i presume this only works on the extreme chips