The author: Victor Rudometov
Evgenie Rudometov

As a rule, such parametres concern:
          Temperature (the processor, the motherboard, air in tank i.d.)
          Supply voltages (the processor, motherboard units etc .),
          Speed of rotation of cooling fans (the processor, a power supply unit
              Etc .).

Fig. 1. The circuit of monitoring of hardware of the computer

Step-by-step resources of hardware monitoring become not only the extremely desirable, but also mandatory attribute of the architecture of modern high-powered and highly reliable systems. Such resources are even more often built in structure of high-powered chip sets.
Unfortunately, architectures of some popular chip sets, for example, i440BX (i440BX AGPset) have no built in resources of hardware monitoring as it is carried out in matching components of modern chip sets which concern, for example, VIA Apollo Pro133A and VIA Apollo KT133A with chips South Bridge VT82C686A and VT82C686B. However, despite lacking in i440BX architecture of similar resources, this possibility in a number of motherboards has been realised by means of special chips, such as LM78 and LM79 National Semiconductor corporations, W83781D and W83782D Winbond corporations. One of such examples of usage of chip Winbond W83782D in the motherboard architecture which basis is the chip set i440BX, is presented on rice 2.

Fig. 2. Inclusion of chips of hardware monitoring and input/conclusion in the architecture of the computer with a chip set i440BX AGPset

It is necessary to mark, that some manufacturers of the motherboards releasing the products on modern chip sets which structure includes resources of hardware monitoring, are not satisfied by their possibilities and use either the specified chips, or similar. So, for example, ASUSTeK corporation which is one of the largest manufacturers of motherboards, rather often applies a monitoring chip own developments. As an example it is possible to result function PC Health Monitoring realised by means of firm chip ASIC (Application Specific Integrated Circuit) AS99127F (fig. 2). By the way, it is frequent similarly this corporation arrives for implementation of network functions, and also of some additional controllers, for example, IEEE1394.

Fig. 3. A monitoring chip on motherboard ASUS CUSL2.

Usage of specialised chips of hardware monitoring speaks quite often in higher parametres on matching with the resources which have been built in components of chip sets. First of all it concerns quantities of controllable parametres and accuracy of their measurement. Last it is the most actual in dispersal modes at usage of the raised powers close to limiting values when essential there are already 100-th shares of volt. The insufficient accuracy of measurements which are carried out by units of hardware monitoring can lead to deformation of results, wrong operations and, as result, to possible rise of probability of mortality of dispersed components of the computer.
As an example of specialised resources of hardware monitoring on fig. 4-5 structures of chips W83782D (W83782D Winbond H/W Monitoring IC) Winbond corporations and LM78/LM79 National Semiconductor corporations are resulted. In these figures circuits of hooking up of sensors and feed variants on input terminals of chips of controllable powers, the various value and polarity are presented also. The resulted chips often use in the architecture of motherboards in chains of hardware monitoring.

Fig. 4. The Inner pattern of chip W83782D and the circuit of hooking up of sensors.

Fig. 5. The Inner pattern of chip LM78 and the circuit of hooking up of sensors.

Basis of the internal arrangement of these and similar chips is the multi-channel 8-bit analogue-digital converter (ADC). It provides input and conversion of 256 values of input signals of positive polarity, for example, 3,3 V.Diapazon analogue-digital converter operations are made 0-4,096 In, and by a quantum — 16 mv (4,096 In / 256). For the extension of a band of an input potential use either internal, or external rezistornye the dividers, which nominals of units depend on controllable levels. It allows to handle powers +5 In and +12 Century
For correct operation of measuring circuits negotiation of their input impedance depending on output impedances of sensors is required. It allows to reach a maximum relation a signal/noise. For negotiation repeaters (grounded collector circuits — OK, the common source — OI etc.) can be used either consecutive resistors, or special electronic circuits, for example  .
It is necessary to mark, that nominals soglasujushchih resistors influence measurement of absolute values of gauged powers. Probably, with it of some the motherboards, linked, for example, some problems of operation of hardware monitoring are linked to indication of the overestimated values of controllable powers. Cases are known when resources of hardware monitoring of the motherboard show power of a kernel of the processor 1,7 In at really installed value 1,65 V.Vozmozhno, it is linked and to unsuccessful circuits additional soglasujushchih cascades, and is possible and with detecting of the interferences which high level, is linked to unsuccessful bussing of similar motherboards.
Except the control of positive powers input and processing of powers of negative polarity is possible also, for example,-5 In and-12 V.Dlja of it as a part of the specified chips operating amplifiers in inverting inclusion that is well visible on circuit LM78/LM79 use. In this case negotiation of entry levels with a demanded band of the analogue-digital converter is carried out by the appropriate resistors defining an input impedance of cascades and the value of feedback of given operating amplifiers. Recommended values of external resistors depending on gauged powers are resulted in the appropriate table.

Recommended values of external resistors depending on gauged powers

The resulted chips allow to gauge and values of temperatures of controllable units for what as sensors use, as a rule, thermistors — the resistors which resistance depends on temperature. Hooking up of these units is carried out usually how it is shown, for example, on the circuit with W83782D (fig. 4). Under the influence of oscillations of the gauged temperature the value of an internal resistance of the thermistor, and consequently, both a current, and power on this unit which is hooked up to a reference voltage through the resistor 10 clod (1 %) varies. Power change on the given thermistor is fixed the analogue-digital converter as a part of a chip of hardware monitoring just as it is carried out at the control of supply voltages.
Instead of the thermistor as the temperature transmitter can use and the transistor in diodnom inclusion, for example, as it is shown on fig. 6 and. The principle of operation of such sensor is grounded on dependence of a threshold voltage of opening of silicon p-p-transition on temperature. As a result of this effect at change of temperature of the transistor-diode the power of a threshold varies practically linearly with negative lapse rate 2,3 мВ/C (dV ~ 1/T). It means, that in the resulted circuit power on the transistor 2N3904, hooked up through the large-value resistor to a reference voltage V REF = 3,6 In, will decrease with temperature growth. By the way, everyone can be convinced of existence of the given effect, having gathered the circuit from consistently jointed diode (for example, КД523) and the resistor 20-30к, 4,5 V.Naprjazhenie hooked up to a standard battery , gauged on the diode, will decrease at heating up by its solder gun (no more than 2-3 seconds).
To similarly variant with the transistor for the control of a temperature functional mode of the processor can be sometimes used and such resources, as, for example, the thermodiode included in structure of a chip of the processor of Pentium III. Usage in the architecture of the processor of the thermodiode instead of the traditional thermistor speaks simply enough. The matter is that in modern difficult chips which the processors concern also, practically all units form on the basis of the p-p-transitions fulfilling not only functions of transistors and diodes, but also resistors, and even capacitors. The recommended minimum value of a current of the built in thermodiode – 5 uA, maximum – 300 uA.
The circuit of hooking up of the built in thermodiode of the processor of Pentium III to chip W83782D is presented on fig. 6 b. The Reference voltage — 3,6 Century

Fig. 6. The hooking up circuit to chip W83782D of semiconducting temperature-sensitive elements:

             And - the transistor 2N3904,
          b - the thermodiode which has been built in a chip of the processor of Pentium III.

Estimating indications of the similar sensor, it is necessary to consider limiting values of temperature of a kernel of processor T1 (Maximum Tjunction) and error amount T2, arising owing to an existing space temperature gradient in a processor chip, and also finite speed of distribution of heat. Considering finiteness of speed of distribution of heat in a processor chip at permanently varying according to oscillations of loading of sites of the processor to space distribution of temperatures, to T2 value implementators recommend to add still an error of measurement of the temperature making approximately 1 With.
Thus, for processors of Pentium III FC-PGA and SC242 (Slot 1) at usage as the temperature sensor of the thermodiode for the value of limiting temperature of operation it is expedient to accept the value equal T1-T2-1.
The thermodiode of the processor of Pentium 4 is in a similar way hooked up also.
At usage as a temperature-sensitive element of the traditional thermistor for the limiting value of temperature of operation of the processor of Pentium III/4 it is expedient to accept value of maximum temperature of tank, a component usually 75 With.

Temperature parametres of processors of Pentium III FC-PGA

Outputs of a temperature-sensitive element of processors of Pentium III/4

Processors AMD Athlon and AMD Duron, and also a product of Intel of early developments have no temperature transmitters built in a chip. Therefore the temperature mode of processors of this type is carried out by means of the external sensors installed usually or near to processors of standards Slot A and Slot 1, or in Socket A plugs (Socket 462) and Socket 370 (fig. 7-8) for processors konstruktiva PGA, FC-PGA, etc. Thus for support of normal operation of temperature-sensitive elements and reception of correct values of temperature of processors implementators of motherboards provide the thermal contact electrode of sensors to tanks of processors. Considering possibility of mechanical deformation or even damage of the mount of temperature-sensitive elements, it is expedient to check quality of the thermal contact electrode.

Fig. 7. The external temperature transmitter of the processor for konstruktiva Slot 1.

 
Fig. 8. The external temperature transmitter of the processor installed inside Socket A.

Considering features of measurement of temperature by means of chips LM78/L79, it is necessary to mark, that as the sensor usage LM75 is recommended. Despite presence only one input terminal for hooking up of an external temperature-sensitive element, there is a possibility of hooking up to 8 arrangements LM75. In this case the choice is carried out by means of usage of appropriate interface lines ISA, I2C: SDA, SCL, A0, A1, A2.
It is necessary to mark, that the resulted and similar chips used in hardware monitoring, do not require carrying out of operations of calibration and, as a rule, the similar resources accessible to users, have no. The correctness and accuracy of operation is reached by usage of sensors and the circuits of hooking up recommended by manufacturers of chips, the architecture of chips, as a rule, provides their programming.
Key parametres of the described chips, and also chips W83781D, W83783S and W83L784R Winbond corporations oriented to application in rather cheap systems and in laptops, are resulted in appropriate tables. For matching key parametres of the integrated resources of hardware monitoring in chip VT82C686A often used as a part of chip sets of VIA corporation are presented also.

Key parametres of chips W83781D, W83782D, W83783S, W83L784R

Key parametres of chips LM78 and LM79

Key parametres of hardware monitoring in VT82C686A

Release of motherboards with implementation of resources of hardware monitoring by means of specialised chips proceeds, despite release abbreviation i440BX and appearance of new chip sets with the improved architecture, Intels developed and released by corporations, VIA, ALi and SiS. The given chip sets differ more difficult construction and wider set of functionality in comparison with i440BX though and quite often concede to it on productivity. In their structure, corporations-implementators, as a rule, enter various resources of monitoring, including hardware monitoring.
Monitoring hardware (hardware monitoring), realised or by means of specialised chips, or built in chip set components, and added with appropriate sensors allow to gauge the set parametres only, as a rule. To carry out the control, output to the screen monitor screen, and also to carry out the necessary analysis of values of these parametres special programs allow. Quite often rather simple programs giving similar tools, are built in in BIOS Setup motherboards. Possibilities of similar resources, number and measurement accuracy of controllable parametres are defined by used chips, sensors, and also versions of program code BIOS. As an example of the built in software of monitoring on fig. 9 menu PC Health Status entering in BIOS Setup popular motherboard Abit BE6-II which basis is made by a chip set i440BX is resulted   .

Fig. 9. Monitoring in BIOS Setup