PC-Chips M571 undocumented voltage settings (V7.0A) - Part 1
The following results are theoretical calculations based on the
published specs of the various devices and on the values observed on the
various resistors. I made no actual voltage measurements since doing so
requires a proper load. Also note that the m/b designers have apparently
allowed for a voltage drop of 70mV between the regulator output and the
CPU socket. Hence the "V at CPU" figure is the one you should be trying
to set.
Some instructions call for a certain resistor at a certain jumper
location. In these cases remove all voltage jumpers and install a
"resistive jumper" on the relevant pins as shown. The gold connector
pins can be obtained by breaking apart an ordinary two-pin PCB jumper
(or by melting away the plastic with a soldering iron?). The bridging
link can be cut and trimmed with sidecutters. Alternatively, use a Reset
or LED connector from an old PC case.
   voltage    gold pins
   header         ||
                  ||     __________
   O  O  O  O  O<>==<>---|resistor|----|      cover resistor and
     JP6           |     |--------|    | <--- pins with heatshrink
   O  O  O  O  O<>==<>-----------------|      tubing
 V at CPU   V at regulator    What to do
 2.19       2.26              all jumpers out
 2.29       2.36              120K resistor at 2V8 jumper location
 2.40       2.47              47K resistor at 2V8 jumper location
 2.51       2.58              22K resistor at 2V8 jumper location
 2.60       2.67              12K resistor at 2V8 jumper location
 2.69       2.76              4.7K resistor at 2V8 jumper location
 2.79       2.86              install 2V8 jumper
 2.90       2.97              install 2V9 jumper
 2.99       3.06              3.9K resistor at 3V2 jumper location
 3.09       3.16              1.8K resistor at 3V2 jumper location
 3.20       3.27              install 3V2 jumper
 3.30       3.37              install 3V3 jumper
 3.40       3.47              1K resistor at 3V5 jumper location
 3.51       3.58              install 3V5 jumper
 3.58       3.65              install 2V9 & 3V3 jumpers
 3.69       3.76              install 2V8, 2V9, 3V2 jumpers
 3.84       3.91              install 3V5 & 3V2 jumpers
 3.88       3.95              install 3V5 & 3V3 jumpers
 4.00       4.07              install 3V5, 3V3, 2V9 jumpers
More accurate voltage selections are possible by fine tuning the
resistor values. Also a better approximation for the 3.8V setting can be
achieved using a combination of one jumper and one resistor. If anyone
needs this to be recalculated, please let me know.

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 This page was last modified on 17 July 2002