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C-States In Multi-Core Processors
In a multi-core processor, there can be multiple C-states in each core, but only one processor C-state is enabled at one time. The processor C-state is equal to the highest C-state of any processing core. Let's say the processor C-state is Cx, and core C-state is CCx, the formula for determining the processor C-state would be :
Cx = max (CCx1, CCx2, CCx3……, CCxn)
Here are some examples :
CPU In C0 State |
CPU In C1 State |
CPU In C2 State |
|
|
|
|
|
|
max (CC0, CC3) |
max (CC1, CC3) |
max (CC2, CC3) |
|
CPU In C3 State |
CPU In C3 State |
CPU In C4 State |
|
|
|
|
|
max (CC3, CC3) |
max (CC4, CC3) |
max (CC4, CC4) |
CPU Power States Summary
Power State |
Execution |
Wake-Up Time |
CPU Power |
Platform |
Core Voltage |
Cache Shrink |
Loss Of Context |
C0 |
Yes |
0ns |
large |
normal |
normal |
no |
no |
C1 |
No |
10ns |
30% |
normal |
normal |
no |
no |
C2 |
No |
100ns |
30% |
no I/O buffer |
normal |
no |
no |
C3 |
No |
50,000ns |
30% |
I/O + no snoop |
normal |
no |
no |
C4 |
No |
160,000ns |
2% |
I/O + no snoop |
C4_VID |
yes |
no |
C5 |
No |
200,000ns |
N/A |
N/A |
C4_VID |
L2 = 0KB |
no |
C6 |
No |
N/A |
N/A |
N/A |
C6_VID |
L2 = 0KB |
yes |
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