PC Chips M571 (V7.0A) undocumented voltage settings - Part 3
 ------------------------------------------------------------
 
 Core voltages less than 2.2V can be obtained by connecting a suitable
 resistor in parallel with R79 as follows (2.0V shown):
 
 
                                  6K04    9K53    20K0 Resistor
                              12K4    8K20    15K8      values
 
                              2V2 3V5 3V3 3V2 2V9 2V8  Jumper ID
     From  _____  _____
     Load  |    \/    |14     R88 R89 R90 R91 R92 R93  Circuit ref
      |    |          |--------|---|---|---|---|---|
      |   1| |\Error  | Vref  |-| |-| |-| |-| |-| |-|
 Vout |----|-| \_Amp  | +5V   | | | | | | | | | | | |  Resistors
       ____|_| /      |       |-| |-| |-| |-| |-| |-|
     V |  2| |/       |        |   |   |   |   |   |
       |   |          |        |   O   O   O   O   O    Jumpers
       |   | KA7500B  |        |   O   O   O   O   O--|  JP6
       |   |__________|        |   |   |   |   |   |  |
       |                       |---|---|---|---|---|  |
       |_______________________|                      |
                               |                      |
                         R79  |-|                    |-|
                         10K2 | |                    | | 47K
                              |-|                    |-|
                               |                      |
                              _|_                    _|_
 
 
 
 In the above case there is a 47K resistor in parallel with R79.
 All other jumpers are removed. The ground side of the 47K resistor
 can be connected to a nearby ground pin such as pin 3 of the speaker 
 connector (J3), pin 5 of the keylock connector (J3), or pin 3 of the 
 fan power connector (J2). The nominal output of the regulator is 2.02V.
 
 For 2.1V (nominal 2.14V), a 100K resistor should be used.
 For 1.9V (nominal 1.93V), a 33K resistor should be used.
 
 The required resistance can be computed using the formula:
 
  R = 126.48 * Vcore / (51- 22.6 * Vcore)
 
 Conversely, a resistance R will produce the following core voltage:
 
  Vcore = 51 * R / (126.48 + 22.6 * R)
 

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 This page was last modified on 17 July 2002