Overclocking Single 1Ghz to 1.33 Ghz

[dopemann]

Hi,

I have a Single 1 Ghz FW800 MDD PowerMac. I somehow manged to get my Bus from 133 to 167 Mhz through OpenFirmware. I found a Script on Google that explained how to get the Dual 867 MDD from 133 to 167 Mhz. Anyway somehow it worked. I now have a CPU Speed of 1.08 Ghz. The CPU is a 7455A with 1MB L3 Cache. I also read that this CPU is used by GigaDesign in their 1.33 Ghz CPU Upgrades, and it runs safe at that Speed. I have also found instructions on how to clock the dual 1.25 Ghz Module to 1.58 Ghz through soldering the jumpers. But those jumpers arent on the 1Ghz Single Module. Does anyone know were these jumpers are and do they have the same value as the ones on the Dual 1.25 Ghz Module? I need a multiplier of 7.5 to get 1.25 Ghz out, and 8 to get 1.33 Ghz out. So if anybody has an Idea the please share it with me. Thanks.

PS. heres the link for those that have a bus of 133 Mhz and want to Try the 167 Mhz setting. forums.macrumors.com/showthread.php?t=12615

[nano2nd]

Interesting - I never knew there was a non-hardware overclock method for the MDD. I might give this a try.

There isn't a lot of user feedback from the linked sites - anyone else have any experience of this?

[vaz]

Hmm, some people had it working with a dual 867 mdd mac..
i wonder if this hack will work on the same board but a Giga dual 1.33Ghz cpu upgrade..so tempted to try it out but dont want to fry the chips lol

[dopemann]

So I investigated it and found a couple of Points that may be of interest. It is Possible to Overclock the CPU of the MDD G4 through OpenFirmware and NVEdit. Basically what it does, its a script that overwrites the ROM values for the BUS-FREQUENCY, CLOCK-FREQUENCY, this script can be undone if you zap the PRAM. The only thing that bugs me is that it may not work FW400 MDD models. It works on FW800 Though. The CLOCK-FREQUENCY can also be changed using this Script, but and now it comes I cant find any Info on the values you have to enter. And the other thing, People who have changed the Bus on the Dual 867 Mhz MDD have a CPU Speed of 1.083 Ghz at the end. Now I have a Single 1Ghz with 133 Mhz Bus Standard, and I get the exact same Frequency when changing the Bus to 167 Mhz, weird? But it has something to do with the values for CLOCK-Frequency on PowerPC,G4@0 and PowerPC,G4@1. Now I want to test some different values for the Script. But I dont have a Single 1.25 Ghz or Dual. Does anyone have a Single or Dual 1.25 Ghz, then do me a favour amd check in IORegistryBrowser wich comes with Xcode 2.3 and CHUD. And check under Root, CPUS, PowerPC G4@0 or 1. Then check the Hex on clock-frequency, timbase-frequency. and if you can find it, bus-frequency and config-bus-frequency. I have also found that if you do have a FW800 MDD the chip wont fry out, because the Mainboard has the 167 Mhz Frequeny but when they were sold in 2003 some Single CPU models only had a 133 Mhz bus Limit. In other words Apple underclockt them.

Here are the values Im using currently with the Script:

CLOCK-FREQUENCY: 408e4b46
BUS-FREQUENCY: 09ef21aa
CONFIG-BUS-FREQUENCY: 09ee81bc
TIMEBASE-FREQUENCY: 027ba06f

Something else I found is iCook, its an App wich can patch the System Kernel to overclock the iBook G3 and some people Report that its possible to overclock the Bus on the G5 since its using some same CPU related technology like the 750fx used in the earlier iBooks.

I want to crack this and if it does work wich in theori it does then no more soldering work on the expensive hardware, wouldnt that be great.

PS: When using IORegistryBrowser use Inspect on the values to get the Hex. Its displayed difrently in the Browser something 0x48 and so on.

Thanks

[vaz]

I'd try it on my Giga dual 1.33 but i dont want Xcode 2.3 and CHUD installed on my system. Had issues with CHUD in the past.
If you can e-mail me the app or show me a link to grab it, i will grab you my values.
VaZ

[B B]

Is this what you are looking for ?
www.xlr8yourmac.com/systems/g4_mirrored_drive_doors/G4_MDD_CPU_Module.html

[dopemann]

Thanks for the links and Replys. I have figured out how it works. It is possible to Overclock your MDD through OpenFirmware. The cool thing is that the Hex is the multiplier. In other words if you enter the Hex for a 1.083 ghz setting its multiplier 6.5, and so on. The only difficult part is that you have to look in the Registry Tree to get the values for the multiplier. So I have the values for 1Ghz, 1.083 Ghz and 1.25 Ghz. So all I need is 1.33 Ghz. Vaz I'll mail you the app and I thank you for the Help. I will list all values as I get them and test them. Again Thanks to all of you who have shown interest in this nifty Overclock helper.

This is for 7455A CPU Modules with 167 Mhz Bus Setting:

3b9ac9fa multiplier 6.0x 1.00 Ghz
408e4b46 multiplier 6.5x 1.083 Ghz
4a817c7b multiplier 7.5x 1.25 Ghz

So I hope this helps.

[dopemann]

Another thing I just observed the Hex for config-bus-frequency, timebase-frequency and bus-frequency, vary on other Macs using the same CPU type such as the macMini 1.25Ghz. The main factor is the clock-frequency Hex.

[dopemann]

I manged to get my single 1Ghz w/133Mhz to 1.25Ghz w/167Mhz stable! And the great news is that my Temp has not yet changed, I'm running at 43-45 C!!! Thats great. 250Mhz over and this result. I'm wondering if Apple underclockt these Machines. So now I'm going all the way and want to try 1.33 Ghz and then 1.42 Ghz.

[ritalin]

dopemann said:

I manged to get my single 1Ghz w/133Mhz to 1.25Ghz w/167Mhz stable! And the great news is that my Temp has not yet changed, I'm running at 43-45 C!!! Thats great. 250Mhz over and this result. I'm wondering if Apple underclockt these Machines. So now I'm going all the way and want to try 1.33 Ghz and then 1.42 Ghz.

I would like to see some before and after benchmarking to confirm the overclock has some real effect. Anyway, good luck with this and be careful not to fry your system.

[dopemann]

I will post them as possible. I'll be using a number of Programs to do the Bench. Xbench and so on. Does anyone know of a good Bench for Graphic cards. I had one but I forgot its name something OpenGL....? I also took look at the Official Freescale documents for the XC7455A CPU, it's speed ranges from 1.0Ghz to 1.33Ghz. They did however mention something in accordance to 1.42 Ghz. But I didn't understand what they were trying to explain.

[ritalin]

OpenGL Extensions Viewer

OpenMark

For the GPU.

[dopemann]

Thanks

[vaz]

Here ya go!
Dual 1.33Ghz/133Mhz
G4@0 & G4@1
"bus-frequency" = <07f0c34e >;
"clock-frequency" = <4f790d52 >;
"config-bus-frequency" = <07f0b5db >;
"cpu-device-type" = MacRISC2CPU;
"timebase-frequency" = <01fc2ac6 >

[vaz]

Yea let us know if Xbench or Cinebench shows any higher scores in the cpu area and memory.