000005 M70. PowerBoard ClockUp
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This is for ,
not for 8580.
*********************************************************************************
40MHz base clock setting for Mod.70
PowerBoard.
Originally written by F355 ( Psudenym
in FIBMJ ) on 1999.04.26
Translated by Sandy on 2000.05.10
Please be advised that F355 and I are
both not responsible for any
damage or inconvenience on your
system with following script.
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1. You need to solder off just * one * of the pins of PLLIC.
Search PLLIC marked IMI SC-427BYB atop on
the chip. It's a tiny SSDP type chip with 10 pins
on each side. It locates around pin #1 of
big blue translucent chip, just between OSC marked H14318
and flash ROM socket.
2. Heat up pin #9 of PLLIC, solder off the pin from the board.
the target pin is "pulled- up" internally
in the chip and if you float the pin from the board, electrical
status of the pin will turn to
*High*.
3. Set J11 jumper to the position for 25MHz operation (
J11= ON ).
Now the output frequency of the PLLIC is 40MHZ. Keep in
mind, Cyrix 100/120/133 in x4 multiplied speed
and DX4-100 may not work. Only am5x86 x4/x3 will
run on the board ( on WinXX ).
( Errm.... There *IS* such CPU, Cyrix 5x86 GP120 x4, actually.
)
Pin out of IMI SC-427BYB
_____________
| o |
Xin = |1
20| = 14.1318MHz
Xout = |2
19| = VDD
Vss = |3
18| = PD2
7.159MHz = |4
17| = VCOin2
S0 = |5
16| = 16NHz
VCOin1 = |6
15| = 32MHz
PD1 = |7
14| = VSS
VDD = |8
13| = MCLK2
S1
= |9 12|
= S2
MCLK1 = |10
11| = TS
|_____________|
"o" is orientation marking.
S1 ( pin #9 ) should
be soldered off from the planar.
Combination of Pin Logic
and Output Frequency
|
Input |
Out Put |
Jumper |
| S2 |
S1 |
S0 |
CPU Base Clock |
J11 |
| 0 |
0 |
1 |
25MHz |
ON |
| 1 |
0 |
1 |
33MHz |
OFF |
| |
|
|
|
|
| 0 |
1 |
1 |
40MHz |
ON |
** S1 is internally high and physically grounded( pulled down
) to Vss in original circuit. So it is always
*LOW*. S0 is
pulled up to Vcc through R255 on the board, It is always *HIGH*.
Changing base clock between
25MHz and 33MHz is done by J11. If the jumper set is ON, S2 will
be grounded *LOW* (=0 ),
while it is OFF then S2 will be *HIgh* ( =1 ).
To get 40MHz, set S1 *HIGH*
( this is done by soldering off the pin #9 from the board ), and
set
S2 *LOW*( J11=ON ).
Attention to you all
PLLIC is very little and pins are very
close to each other. Furthermore 14.318 OSC locates very
close to PLLIC.
Be careful not to break off the pin,
nor to make a bridge between pins by your soldering iron.
Otherwise your system will not work
on 25/33MHz anymore. It may cause fatal errors on your
expensive PowerBoard.
DO IT WITH YOUR OWN RISK ! NO ONE
WILL BE RESPONSIBLE BUT YOU.
and
TAKE CARE !
If anybody wants to amend above method to *CORRECT*
English, please do it.
If you can connect lead wires to floated pin
#9 and it's solder land each, and set jumper pins on the
other end, you can change back to normal
setting with shorting the jumper pins.
About Mod.80 Powerboard.
PLLIC used in Mod.80 board is IC DESIGNS 2028SC-B.
I have no pin-out for it.
Still Crazy Top
PS/55 Index
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