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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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lm_sensors versions through 2.6.3 support only the VRM 8.2 standard. |
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Starting in lm_sensors 2.6.4 the VRM version is configurable. |
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To configure the sensor chip for the correct voltage range, |
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you must set the "vrm" correctly either via /proc, /sys, or sensors.conf. |
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To change the vrm version to 9.0, for example, do the following |
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after the chip module (in this example, w83781d) is loaded: |
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(kernel 2.4) |
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echo 9.0 > /proc/sys/dev/sensors/w83781d-isa-0290/vrm |
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(kernel 2.6 up to 2.6.13) |
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echo 90 > /sys/bus/i2c/devices/0-0290/vrm |
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(kernel 2.6.14 and later) |
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echo 90 > /sys/class/hwmon/hwmon0/device/vrm |
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Alternatively, add a line in /etc/sensors.conf in the w83781d section |
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(you should put this line BEFORE any line that uses vid in a calculation): |
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set vrm 9.0 |
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and then, after the chip module is loaded, do: |
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sensors -s |
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After this, reading the vid either by |
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(kernel 2.4) |
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cat /proc/sys/dev/sensors/w83781d-isa-0290/vid |
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(kernel 2.6 up to 2.6.13 - divide the output by 1000) |
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cat /sys/bus/i2c/devices/0-0290/cpu0_vid |
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(kernel 2.6.14 and later - divide the output by 1000) |
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cat /sys/class/hwmon/hwmon0/device/cpu0_vid |
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or by |
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sensors |
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should show the new vid value. |
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The following values are legal vrm values. Other values will be |
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allowed but will result in using the 8.2 standard. |
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2.4, 8.1-8.5, 9.0, 9.1, 10.0 |
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Remember, the VID pins on the sensor chips are inputs only. |
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That means they can't be changed and there shouldn't be |
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any problems if you experiment with the vrm values until you |
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get it right. You cannot manipulate the actual processor core |
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voltage through lm_sensors drivers. |
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Not all sensor chips have VID inputs. |
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For those that do, the VRM support status is listed below. |
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The following chip drivers support all the VRM versions via |
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/etc/sensors.conf and the vrm entry in /proc or /sys: |
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adm1025, adm1026, asb100, lm85, lm87, pc87360, |
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vt1211, vt8231, w83627ehf, w83627hf, w83781d, w83792d |
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The following chip drivers support only VRM 8.2 and cannot be changed: |
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adm1024, it87, mtp008, adm9240, gl520sm, lm78 |
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If you have a board with one of these chips which needs advanced |
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VRM support please email us. |
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The following chip drivers support only VRM 10.0 and cannot be changed: |
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lm93 |
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------------------ |
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Copyright (c) 2002-2004 Mark D. Studebaker |
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