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VID pin settings |
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-------------------- |
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The VID (Voltage Identification) pins on sensor chips |
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are used to read the CPU Core voltage setting. |
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The VID setting can be controlled by jumpers on the board, |
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or, in newer motherboards, by settings in the BIOS. |
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On these newer boards, the BIOS programs some device's |
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pins which in turn controls a DC-DC Converter to set its |
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output to a certain voltage. These pins are also connected to |
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the sensor chip so that the VID setting can be read back |
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by applications. |
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There are generally 5 VID pins. Recent motherboards may use 6 pins. |
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The VID codes are defined by Intel in documents titled |
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"VRM X.X DC-DC Converter Design Guidelines". |
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(VRM = Voltage Regulator Module), or |
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"Voltage Regulator-Down (VRD) 10.0 Design Guide". |
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These documents are available at http://developer.intel.com. |
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There are several different VRM document versions. |
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The common versions are as follows: |
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Document Version Voltage Range Increment Processors |
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---------------- ------------- --------- ---------- |
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"2.4" 0.8 - 1.55 0.025V AMD Opteron 24x |
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8.2 (8.1, 8.3) 1.30 - 2.05V 0.05V PII, PIII, Celeron |
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2.1 - 3.5V 0.10V |
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8.4 1.30 - 2.05V 0.05V PIII, Celeron |
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4 pins only |
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8.5 1.050 - 1.825V 0.05V PIII-S Tualatin |
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9.0, (9.1) 1.100 - 1.850V 0.025V P4, AMD Socket A |
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10.0 0.8375 - 1.6000 0.0125V Desktop Socket 478 |
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"2.4" is not an actual document version but simply a way to identify |
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AMD Opteron 24x processors. |
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Note that versions 8.1 - 8.4 are compatible. |
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Since Linux 2.6.9, the correct VRM version is selected automatically |
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based on the CPU brand and model. Thus you shouldn't have to care about |
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it. If you are using a brand new CPU and even the latest kernel complains |
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("Unknown VRM version of your CPU"), this means that the kernel must be |
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taught about this new CPU model. Please report to us in this case. |
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Remember, the VID pins on the sensor chips are inputs only. |
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You cannot use them to manipulate the actual processor core voltage. |
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------------------ |
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Copyright (c) 2002-2004 Mark D. Studebaker |
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