| 1 | VID pin settings |
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| 2 | -------------------- |
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| 3 | |
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| 4 | The VID (Voltage Identification) pins on sensor chips |
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| 5 | are used to read the CPU Core voltage setting. |
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| 6 | |
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| 7 | The VID setting can be controlled by jumpers on the board, |
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| 8 | or, in newer motherboards, by settings in the BIOS. |
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| 9 | On these newer boards, the BIOS programs some device's |
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| 10 | pins which in turn controls a DC-DC Converter to set its |
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| 11 | output to a certain voltage. These pins are also connected to |
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| 12 | the sensor chip so that the VID setting can be read back |
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| 13 | by applications. |
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| 14 | |
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| 15 | There are generally 5 VID pins. Recent motherboards may use 6 pins. |
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| 16 | The VID codes are defined by Intel in documents titled |
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| 17 | "VRM X.X DC-DC Converter Design Guidelines". |
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| 18 | (VRM = Voltage Regulator Module), or |
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| 19 | "Voltage Regulator-Down (VRD) 10.0 Design Guide". |
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| 20 | These documents are available at http://developer.intel.com. |
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| 21 | |
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| 22 | There are several different VRM document versions. |
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| 23 | The common versions are as follows: |
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| 24 | |
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| 25 | Document Version Voltage Range Increment Processors |
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| 26 | ---------------- ------------- --------- ---------- |
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| 27 | "2.4" 0.8 - 1.55 0.025V AMD Opteron 24x |
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| 28 | |
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| 29 | 8.2 (8.1, 8.3) 1.30 - 2.05V 0.05V PII, PIII, Celeron |
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| 30 | 2.1 - 3.5V 0.10V |
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| 31 | |
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| 32 | 8.4 1.30 - 2.05V 0.05V PIII, Celeron |
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| 33 | 4 pins only |
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| 34 | |
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| 35 | 8.5 1.050 - 1.825V 0.05V PIII-S Tualatin |
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| 36 | |
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| 37 | 9.0, (9.1) 1.100 - 1.850V 0.025V P4, AMD Socket A |
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| 38 | |
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| 39 | 10.0 0.8375 - 1.6000 0.0125V Desktop Socket 478 |
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| 40 | |
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| 41 | |
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| 42 | "2.4" is not an actual document version but simply a way to identify |
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| 43 | AMD Opteron 24x processors. |
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| 44 | Note that versions 8.1 - 8.4 are compatible. |
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| 45 | |
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| 46 | lm_sensors versions through 2.6.3 support only the VRM 8.2 standard. |
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| 47 | |
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| 48 | Starting in lm_sensors 2.6.4 the VRM version is configurable. |
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| 49 | To configure the sensor chip for the correct voltage range, |
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| 50 | you must set the "vrm" correctly either via /proc, /sys, or sensors.conf. |
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| 51 | |
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| 52 | Since Linux 2.6.9, the correct VRM version is selected automatically |
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| 53 | based on the CPU brand and model. For older kernels, you must set the |
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| 54 | correct VRM version yourself. |
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| 55 | |
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| 56 | To change the vrm version to 9.0, for example, do the following |
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| 57 | after the chip module (in this example, w83781d) is loaded: |
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| 58 | |
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| 59 | (kernel 2.4) |
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| 60 | echo 9.0 > /proc/sys/dev/sensors/w83781d-isa-0290/vrm |
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| 61 | (kernel 2.6 up to 2.6.13) |
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| 62 | echo 90 > /sys/bus/i2c/devices/0-0290/vrm |
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| 63 | (kernel 2.6.14 and later) |
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| 64 | echo 90 > /sys/class/hwmon/hwmon0/device/vrm |
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| 65 | |
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| 66 | Alternatively, add a line in /etc/sensors.conf in the w83781d section |
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| 67 | (you should put this line BEFORE any line that uses vid in a calculation): |
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| 68 | |
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| 69 | set vrm 9.0 |
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| 70 | |
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| 71 | and then, after the chip module is loaded, do: |
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| 72 | |
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| 73 | sensors -s |
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| 74 | |
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| 75 | After this, reading the vid either by |
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| 76 | |
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| 77 | (kernel 2.4) |
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| 78 | cat /proc/sys/dev/sensors/w83781d-isa-0290/vid |
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| 79 | (kernel 2.6 up to 2.6.13 - divide the output by 1000) |
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| 80 | cat /sys/bus/i2c/devices/0-0290/cpu0_vid |
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| 81 | (kernel 2.6.14 and later - divide the output by 1000) |
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| 82 | cat /sys/class/hwmon/hwmon0/device/cpu0_vid |
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| 83 | |
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| 84 | or by |
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| 85 | |
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| 86 | sensors |
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| 87 | |
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| 88 | should show the new vid value. |
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| 89 | |
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| 90 | |
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| 91 | The following values are legal vrm values. Other values will be |
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| 92 | allowed but will result in using the 8.2 standard. |
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| 93 | |
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| 94 | 2.4, 8.1-8.5, 9.0, 9.1, 10.0 |
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| 95 | |
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| 96 | |
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| 97 | Remember, the VID pins on the sensor chips are inputs only. |
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| 98 | That means they can't be changed and there shouldn't be |
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| 99 | any problems if you experiment with the vrm values until you |
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| 100 | get it right. You cannot manipulate the actual processor core |
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| 101 | voltage through lm_sensors drivers. |
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| 102 | |
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| 103 | Not all sensor chips have VID inputs. |
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| 104 | For those that do, the VRM support status is listed below. |
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| 105 | |
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| 106 | The following chip drivers support all the VRM versions via |
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| 107 | /etc/sensors.conf and the vrm entry in /proc or /sys: |
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| 108 | |
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| 109 | adm1025, adm1026, asb100, lm85, lm87, pc87360, |
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| 110 | vt1211, vt8231, w83627ehf, w83627hf, w83781d, w83792d |
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| 111 | |
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| 112 | |
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| 113 | The following chip drivers support only VRM 8.2 and cannot be changed: |
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| 114 | |
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| 115 | adm1024, it87, mtp008, adm9240, gl520sm, lm78 |
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| 116 | |
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| 117 | The following chip drivers support only VRM 10.0 and cannot be changed: |
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| 118 | |
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| 119 | lm93 |
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| 120 | |
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| 121 | ------------------ |
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| 122 | Copyright (c) 2002-2004 Mark D. Studebaker |
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