PC Chips M571 (V7.0A) undocumented voltage settings - Part 3
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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)
This page was last modified on 17 July 2002