root/lm-sensors/trunk/doc/vid

Revision 5626, 2.1 KB (checked in by khali, 5 years ago)

There can be more than 6 VID pins.

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1VID pin settings
2--------------------
3
4The VID (Voltage Identification) pins on sensor chips
5are used to read the CPU Core voltage setting.
6
7The VID setting can be controlled by jumpers on the board,
8or, in newer motherboards, by settings in the BIOS.
9On these newer boards, the BIOS programs some device's
10pins which in turn controls a DC-DC Converter to set its
11output to a certain voltage. These pins are also connected to
12the sensor chip so that the VID setting can be read back
13by applications.
14
15There are between 4 and 8 VID pins (the more recent the CPU, the more
16numerous the VID pins.) The VID codes are defined by Intel in documents
17titled "VRM X.X DC-DC Converter Design Guidelines".
18(VRM = Voltage Regulator Module), or
19"Voltage Regulator-Down (VRD) X.X Design Guide".
20These documents are available at http://developer.intel.com.
21There are equivalent documents for AMD processors (look for a table
22named "VID Code Voltages" in processor specifications.)
23
24There are several different VRM document versions.
25The common versions are as follows:
26
27Document Version        Voltage Range   Increment       Processors
28----------------        -------------   ---------       ----------
29"2.4"                   0.8 - 1.55      0.025V          AMD Opteron 24x
30
318.2 (8.1, 8.3)          1.30 - 2.05V    0.05V           PII, PIII, Celeron
32                        2.1 - 3.5V      0.10V
33
348.4                     1.30 - 2.05V    0.05V           PIII, Celeron
35                                                        4 pins only
36
378.5                     1.050 - 1.825V  0.05V           PIII-S Tualatin
38
399.0, (9.1)              1.100 - 1.850V  0.025V          P4, AMD Socket A
40
4110.0                    0.8375 - 1.6000 0.0125V         Desktop Socket 478
42
43
44"2.4" is not an actual document version but simply a way to identify
45AMD Opteron 24x processors.
46Note that versions 8.1 - 8.4 are compatible.
47
48Since Linux 2.6.9, the correct VRM version is selected automatically
49based on the CPU brand and model. Thus you shouldn't have to care about
50it. If you are using a brand new CPU and even the latest kernel complains
51("Unknown VRM version of your CPU"), this means that the kernel must be
52taught about this new CPU model. Please report to us in this case.
53
54Remember, the VID pins on the sensor chips are inputs only.
55You cannot use them to manipulate the actual processor core voltage.
56
57------------------
58Copyright (c) 2002-2004 Mark D. Studebaker
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