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View Full Version : Help with Pismo FSB Overclocking


Plutonique9
Sep 28, 2004, 06:43 PM
I've been looking into overclockng the FSB in the Powerbook G3 2000 (Pismo) from 100mhz to 133mhz. Of course, the only information I found online was in reference to changing the CPU clock multipliers, not the FSB clock multipliers.

So I found out what is responsible for setting the Motherboard FSB frequency, which is the Z9104DAB IC on the removable CPU board. The Datasheet is found here;

http://www.imicorp.com/cfuploads/img/products/IMIZ9104DAB.pdf

Looking at the datasheet, it seems like the Clock is only able to output from 30mhz to 100mhz (The Pismo uses the 3.0 Multiplier (33.3mhz x 3). This initially seems like then there is no way to overclock the FSB, which probably explains the lack of information online.

ĽOn second look the overview says;

Output frequencies from 30 to 120 MHz
http://www.imicorp.com/products/datasheet.cfm?partnum=IMIZ9104

However, I thought it may be possible to increase the Z9104 reference clock from 33.3mhz to something higher. The output clock of the Z9104 is determined by the onboard multiplier and the reference clock, so perhaps increasing the reference to 44.4mhz would output a FSB frequency of 133mhz?

But then again, perhaps it would cause strange timings in the Powerbook, maybe?

I think I've found 2 crystals on the Pismo CPU board which may be the SMD reference clock. There are to SMD components on the CPU side of the daughtercard labled L1 & L2.

Of course, in in order to function properly, you'd still have to decrease the CPU multiplier and the L2 cache ratio.

It seems the Powerbook G4 500mhz uses the Z9104 and i found a japanese page which talks about, deciphered using babelfish, increasing the reference crystal to 40mhz. However, babelfish falls short in provinding anything further thats understandable.

http://homepage.mac.com/stworld/stw/index2.html

Anyone more knowledgable?

ryanOutput frequencies from 30 to 120 MHz