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MDD Overclocking Guide


** DISCLAIMER **

Altering any part of your OS or computer will void your warranty and may damage your computer. These modifications are for educational purposes only and are performed at the owners risk - This site or it's owner are not responsible for any damage caused.


I have yet to find a website that outlines how to overclock your MDD G4 in a step by step format. Through a lot research and testing I am confident that the information and pictures provided will allow even a novice with moderate soldering skills to perform the overclock. Be aware that if you do not have the confidence to do this, then you probably shouldn't.

 

(This guide assumes you are overclocking a 167MHz bus model MDD (1GHz, 1.25GHz or 1.42GHz). 867MHz models use a 133MHz bus.)

Tools you will need:

 - Antistatic Wrist Strap

 - Variable temperature soldering station with pencil tip - Regular soldering irons will be ok too but a soldering station is preferred

 - Philips screwdriver

 - Tweezers

 - Magnifying glass (optional)

 - Thermal paste

 

Step 1. Remove the heatsink and then the processor board from your MDD and clean away any heat transfer paste from the CPU cores. You should have something in front of you that looks like this

 

Step 2. Locate the following resistor locations as this is where the modifications will occur. There are 5 multiplier locations on the front of the processor board for one CPU and also 5 multiplier locations on the reverse side of the board for the second CPU. Whatever multipliers you choose, it must be the same for both CPU's or the system will not boot.

 

Front location

 

Rear location - Picture also shows CPU voltage regulator resistors marked "VID[0-4]"

 

 

Step 3.   The table below outlines the PLL_EXT and PLL_CFG[0-3] settings for different bus and CPU speeds. For this example I am starting with a stock 1250MHz speed (7.5x multiplier) setting and upgrading to 1500MHz (9x multiplier) setting. The first number in the fields of the first column represents the PLL_EXT resistor and the following 4 numbers represent PLL_CFG[0], PLL_CFG[1], PLL_CFG[2] and PLL_CFG[3] resistors.

Example: 167MHz system bus and 1250MHz (7.5x multiplier) CPU speed is represented as:

PLL_EXT = 0 (resistor or bridged)

PLL_CFG[0] = 0 (resistor or bridged)

PLL_CFG[1] = 0 (resistor or bridged)

PLL_CFG[2] = 0 (resistor or bridged)

PLL_CFG[3] = 1 (no resistor or open)

Our target speed is 1500MHz (9x multiplier) - This is represented as:

PLL_EXT = 1 (no resistor or open)

PLL_CFG[0] = 0 (resistor or bridged)

PLL_CFG[1] = 1 (no resistor or open)

PLL_CFG[2] = 1 (no resistor or open)

PLL_CFG[3] = 1 (no resistor or open)

    PLL Multiplier Config + Actual Speed on given bus      
PLL_EXT+PLL[0-3]
0=Closed
1=Open
Multiplier
50MHz Bus Clock 66MHz Bus Clock 100MHz Bus Clock 133.33MHz Bus Clock 166.66MHz Bus Clock
00100
2x
100MHz 133MHZ 200MHz 267MHz 333MHz
00110
2.5x
125MHz 166MHz 250MHz 333MHz 417MHz
01000
3x
150MHz 200MHz 300MHz 400MHz 500MHz
01110
3.5x
175MHz 233MHz 350MHz 467MHz 583MHz
01010
4x
200MHz 266MHz 400MHz 533MHz 667MHz
00111
4.5x
225MHz 300MHz 450MHz 600MHz 750MHz
01011
5x
250MHz 333MHz 500MHz 667MHz 833MHz
01001
5.5x
275MHz 366MHz 550MHz 733MHz 917MHz
01101
6x
300MHz 400MHz 600MHz 800MHz 1000MHz
00101
6.5x
325MHz 433MHz 650MHz 867MHz 1083MHz
00010
7x
350MHz 466MHz 700MHz 933MHz 1167MHz
00001
7.5x
375MHz 500MHz 750MHz 1000MHz 1250MHz
01100
8x
400MHz 533MHz 800MHz 1067MHz 1333MHz
00110
8.5x
425MHz 566MHz 850MHz 1133MHz 1417MHz
10111
9x
450MHz 600MHz 900MHz 1200MHz 1500MHz
00111
9.5x
475MHz 633MHz 950MHz 1267MHz 1583MHz
11010
10x
500MHz 667MHz 1000MHz 1333MHz 1667MHz
11000
10.5x
525MHz 700MHz 1050MHz 1400MHz 1750MHz
11001
11x
550MHz 733MHz 1100MHz 1467MHz 1833MHz
00000
11.5x
575MHz 766MHz 1150MHz 1533MHz 1917MHz
11011
12x
600MHz 800MHz 1200MHz 1600MHz 2000MHz
11111
12.5x
625MHz 833MHz 1250MHz 1667MHz 2083MHz
10101
13x
650MHz 867MHz 1300MHz 1733MHz 2167MHz
01110
13.5x
675MHz 900MHz 1350MHz 1800MHz 2250MHz
11100
14x
700MHz 933MHz 1400MHz 1867MHz 2333MHz
10001
15x
750MHz 1000MHz 1500MHz 2000MHz 2500MHz
11101
16x
800MHz 1067MHz 1600MHz 2133MHz 2667MHz
00011
PLL off/bypass (1x bus to core implied)
50MHz 66MHz 100MHz 133MHz 167MHz
01111
PLL off
0MHz 0MHz 0MHz 0MHz 0MHz

 

Close up of the multiplier resistor locations @ 1500MHz (front)

 

Close up of the multiplier resistor locations @ 1500MHz (rear)

 

 

Step 4. You will notice that all the resistors that were originally in these locations have been removed. This was done by using a soldering iron and a pair of tweezers to gently pry the resistors off the contacts of the board. You do not have to do this if you know your target CPU speed. I removed them because I tested a lot of different speeds and it just made it easier to remove them all.

To remove a resistor, just heat each side of it for 1 second at a time until it loosens - A lot of patience is needed here as forcing the resistor off without proper heating can result in damage to the contact.

You can choose to re-solder these resistors as you wish but I find it just a bit too fiddley (they are painfully small). I instead use a small ball of solder to bridge the contacts as you can see in the above photo (PLL_CFG[0]).

 

 

Step 5. The voltage regulator multipliers work on the exact same principal as CPU multipliers. The table of voltages is listed below including the default settings of a 2003 Dual 1.25GHz MDD.

(This last step is not necessary for most minor overclocks, 1500MHz @ 1.55V (default) probably being the limit of a stock 1250MHz processor (7455B). Anything higher will require a voltage boost to be stable.)

      

    Core Supply Voltage Settings (for 1250MHz CPU's only) 
VID[0-4] Vdd [V] Comments
11110 1.30  
01110 1.35  
10110 1.40  
00110 1.45  
11010 1.50  
01010 1.55 default (for DP1.25 - 2003)
10010 1.60  
00010 1.65  
11100 1.70  
01100 1.75  
10100 1.80  
00100 1.85  
11000 1.90  
01000 1.95  
10000 2.00  

 

A close up picture of the voltage resistor settings for the 1250MHz CPU module (1.60V shown below)

This is the pin allocation for the above voltage regulator (1250MHz module)


This section refers to 1420MHz modules only

Below is the multiplier table for the 3-Phase LTC3732CG - Note the default voltage for the 1420MHz module is 1.60V

A closeup of the voltage regulator for the 1420MHz processor module

 and the corresponding pin allocation

 

Step 6. Double check your solder joins and multiplier settings and reinstall the processor board. Be sure to apply thermal paste (such as Arctic Silver 5) to both CPU cores before re-seating the heatsink.

Power up the G4. If you hear the signature Mac startup chime, you have succeeded. If not remove everything and check your solder joins or try bringing down the processor speed a notch - If you overclock too high your machine will not boot.


 

 

Extra Pictures

A close up picture of the very clockable Motorola 1250MHz 7455B processor

 

The 1400MHz 7455B

 

One of the 1Mb Samsung Cache modules

 

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