PCchips M571LMR core voltage regulator
--------------------------------------
WARNING: The following information has not been properly tested and may
contain errors.
The following schematic diagram is of the core voltage regulator on the
M571LMR motherboard. Transistors Q17, Q15, Q19, and Q20 provide binary
weighted contributions of 0.1V, 0.2V, 0.4V, and 0.8V, respectively, to
the overall core voltage setting.
Undocumented header J9 appears to be intended for manufacturing tests.
By means of jumper wires, this header can be used to override the BIOS
core voltage settings. Pin 6 can also be used as a convenient Vcore test
point.
Note that the transistors are NPN types, part number ZS94 (?), and that
their emitters are connected to ground. Furthermore, when turned on
their VCE is of the order of 8 or 9mV.
Note that the minimum Vcore is set by turning off all four transistors.
This minimum is calculated from the formula:
Vcore (min) = (8K06 + 4K99) / 8K06 x 1.25
= 2.02V
_____ Vcore
|
_|_
85B 18C 47C 75C | | 68B
7K45 14K85 30K1 60K4 |_| 4K99 |\
________________________________|________5| \
| | | | | | E\ KA34063
_|_ _|_ _|_ _|_ | 1.25V--| / error amp
| | | | | | | | | Vref | /
|_| |_| |_| |_| | |/
| | | | |
| | | |C _|_
|/ |/ |/ B|/ | | 88B
|--| |--| |--| |--| |_| 8K06
| |\ | |\ | |\ | |\ |
| | | | | | | |E |
| |__|____|__|____|__|____|_______|
| | | | |
| Q20 | Q19 | Q15 | Q17 _|_
| | | | =
| | | | __
| | | |---|__|---->
| | | | __
| | |-----------|__|---->
| | | | __ to chipset
| |-------------------|__|---->
| | | | __
|---------------------------|__|---->
| | | | 10K resistor
| | | | pack
| | | |
J9-4 J9-3 J9-2 J9-1
0.8V 0.4V 0.2V 0.1V
J9 pinout
---------
Q20 -----| |------ Vcore
Q15 --| | | |--- Key
| | | |
|--|--|--|--|
|2 |4 |6 |x |
|--|--|--|--|
|1 |3 |5 |7 |
|--|--|--|--|
| | | |
| | | |
Q17 --| | | |--- +5V
Q19 -----| |------ Ground
How to obtain a Vcore of 1.9V for certain AMD CPUs
--------------------------------------------------
This can be done by forcing all transistors off, and by placing a
suitable resistor in parallel with the 4K99 resistor. The value of this
resistor, R, can be calculated from the formulae:
1/R = 1.25 / 8.06 / (Vcore - 1.25) - 1 / 4.99
Vcore = 1.25 + 1.25 / 8.06 x R x 4.99 / (R + 4.99)
A value of 27K gives a Vcore of 1.90V, while 33K results in 1.92V.
To turn all transistors off, make up an 8-pin double row connector for
J9 by wiring pins 1,2,3,4, and 5 together. Run a separate wire from J9-6
to your new resistor, and wire the other end of this resistor to pin 5
of IC KA34063. Alternatively, ensure that a core voltage of 2.0V is
selected in the BIOS setup.
This page was last modified on 17 July 2002