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Doward
May 21, 2013, 11:39 PM
Anyone know offhand which resistor bank controls PLL? iMac 17" 800Mhz G4. Looking to move it up to 900Mhz is all.

Thanks!



justperry
May 21, 2013, 11:50 PM
Don't even bother, I overclocked my Pismo long time ago, from 500 to 550 MHz, unstable and does not make much of a difference.
I said it before and say it again, if you want a faster Mac buy a faster Mac, overclocking does not give you much of a speed boost.
Even a PATA/IDE SSD would do more than overclocking.

666sheep
May 22, 2013, 12:12 AM
Don't spread defeatism Perry ;) :p

OP: here you go http://thundernerd.com/iMacG4Chart.html

Been here, done that. New decent thermal paste and good dusting is a must.

Doward
May 22, 2013, 08:56 AM
Don't spread defeatism Perry ;) :p

OP: here you go http://thundernerd.com/iMacG4Chart.html

Been here, done that. New decent thermal paste and good dusting is a must.

Much obliged, sir! Freebie system needs a little Leopard breathed into it. Now to dig through the old ram, see if I can make 1GB out of it ;)

*edit*

Very interesting. Cleaned the CPU, and I've got an XPC7451 800Mhz - not an XPC 7450 800Mhz. Wonder if 1Ghz might be in the cards ;) Also noticed I do have two points that the heatsink interfaces with the casing (dual heat pipes).

I may go for 1Ghz, see if she's stable.

keysersoze
May 22, 2013, 01:24 PM
[QUOTE=Doward;17300403]Much obliged, sir! Freebie system needs a little Leopard breathed into it. QUOTE]

I imagine you know this, but just throwing out there on the off chance you don't... you can still install Leopard on a 800 Mhz iMac G4... without overclocking to reach the 867 cutoff. LeopardAssist to the rescue!

http://leopardassist.sourceforge.net/supported.html

Anyway, good luck with your project

Doward
May 22, 2013, 01:31 PM
[QUOTE=Doward;17300403]Much obliged, sir! Freebie system needs a little Leopard breathed into it. QUOTE]

I imagine you know this, but just throwing out there on the off chance you don't... you can still install Leopard on a 800 Mhz iMac G4... without overclocking to reach the 867 cutoff. LeopardAssist to the rescue!

http://leopardassist.sourceforge.net/supported.html

Anyway, good luck with your project

Certainly, but where's the fun in that? Going to see if I can push this little 800Mhz up to 1Ghz. A 25% increase in speed would be nice :)

666sheep
May 22, 2013, 02:14 PM
Very interesting. Cleaned the CPU, and I've got an XPC7451 800Mhz - not an XPC 7450 800Mhz. Wonder if 1Ghz might be in the cards ;) Also noticed I do have two points that the heatsink interfaces with the casing (dual heat pipes).

I may go for 1Ghz, see if she's stable.

There's no substantial difference between 7450 and 7451. Only some bugs were fixed. Check this out if you're interested: http://www.freescale.com/files/32bit/doc/errata/MPC7450CE.pdf
1 GHz is no go, I'm afraid, I've tried... 900 was stable on few, unstable on other ones (about 60/40).
Motorola/Freescale has never clocked 7451 higher than 867 MHz. But there is a small headroom as usual.

Doward
May 22, 2013, 04:29 PM
There's no substantial difference between 7450 and 7451. Only some bugs were fixed. Check this out if you're interested: http://www.freescale.com/files/32bit/doc/errata/MPC7450CE.pdf
1 GHz is no go, I'm afraid, I've tried... 900 was stable on few, unstable on other ones (about 60/40).
Motorola/Freescale has never clocked 7451 higher than 867 MHz. But there is a small headroom as usual.

Interesting. I thought the 7451 was part of the 'Apollo 6' family (ala 7455, etc) while the 7450 was Voyager?

MaxHeap
May 25, 2013, 09:26 PM
On any G4 overclock, do you actually have to use the resistors or would jumping it with just solder work? Have a 867 MHz Quicksilver I may want to perform surgery on. :)

666sheep
Jun 7, 2013, 08:41 AM
On any G4 overclock, do you actually have to use the resistors or would jumping it with just solder work? Have a 867 MHz Quicksilver I may want to perform surgery on. :)

Jumping with solder works well. Resistor isn't a must.

Doward
Jun 8, 2013, 07:10 PM
Correct, or you can use a thin strand wire and solder both sides of it down. :)

g4dg3t
Feb 12, 2014, 04:23 PM
Any luck overclocking your iMac G4? i have an 800mhz one that i was thinking about trying. I'm a little weary about bringing a soldering iron to it. i hear that going from 800 to 900 has only a 60/40 chance of being stable. Please post your results when you try it :)

Hughmac
Feb 12, 2014, 04:35 PM
Correct, or you can use a thin strand wire and solder both sides of it down. :)

Or, you can use conductive paint (such as is used to repair rear screen heater elements in cars).
Use a pin and magnifying glass to apply it, and make sure it's dry before firing the Mac up.

Cheers :)

Hugh

PS I must be one of the lucky ones, I've done a Pismo 400 to 450 and a Pismo 500 to 550 (both stable), using the above method.