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G4 CPU replacement

macz1

macz1

macrumors 6502
Original poster
Oct 28, 2007
315
5
Hello, has anybody of you ever tried to exchange the CPU of a Sawtooth Powermac G4 with a Quicksilver CPU?
I would like to implant a 800MHz QS CPU into my G4/400 hoping for some moderate speed gain...

It seems that I have to remove the CD ATA connector (or move it, with some soldering work...) but I don't want to do it if this CPU is known not to work in this configuration...
The pins of the daughter card seem identical for both CPUs at least.
 
Check if your G4 will support dual CPUs, if it will then get a dual 500mhz card on eBay for about $45.
 
CubeHacker said:
It will not work. Totally different FSB speeds, different voltages.
Click to expand...

The Bus speed problem can easily be corrected by setting the PLL ratio from 6 to 8 moving some resistors on the QS CPU. (100 vs 133 bus freq)
But where do you know from that these CPUs operate at different voltages? aren't these regulated on the daughter card?

And I already checked it, unfortunately my G4 does not support dual CPUs...

PS: I do not want to buy an extra CPU upgrade. I only wanted to check whether this QS CPU can be used in my Sawtooth instead of laying around.
 
success!

OK, I did it. After some struggle attempting to remove the ata connector, the Quicksilver CPU works in my Sawtooth...

I did not make any detailed speed comparisons yet, but it seems to be a little faster, but not much more than a little, unfortunately...
I think the effect of the higher clock speed (from 400 to 800 MHz) is offset by the small cache of the QS CPU (from 1M to 256K)

I will probably do some benchmarks sooner or later in order to decide which cpu to keep...
 
To simplify what has been said putting it in plain English there are 100 megahertz mother boards and 133 mhz mother boards whatever processor you buy from OWC comes with a chart that shows how to set the little tiny switches in order to make it work for which mother board (or BUS) you have. Set the little tiny switches in the chart provided with the new cpu to the settings for your specific motherboard at the rate of speed in GHZ for the processor as you ordered it if you set it to a higher speed you could burn the damn thing out and void the warranty.
 
Shake 'n' Bake said:
Correct me if I'm wrong, but couldn't you get a QS logic board off eBay and swap it?
Click to expand...

I don't know if that would work, probably you will have some trouble with the board dimensions.
But in principle, this should work because you would basically replace everything except the drives...
 
macz1 said:
I don't know if that would work, probably you will have some trouble with the board dimensions.
But in principle, this should work because you would basically replace everything except the drives...
Click to expand...

The QS and Sawtooth both had essentially the same case. I can't find the dimension anywhere.
 
I did now some short tests with the new CPU and it seems to bring a nice speedup...

The time for rendering a scene in cinema 4d dropped from 1:10 to 0:45 and safari feels noticeably faster...
It's better than I expected, the small L2 cache could have a bigger impact...
I'll can post some pictures if anyone is interested.
 
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