Mac G4 processor exchange.

Hi, I have a G4 . It was the last model built. 1.25 Single processor, 2 gigs ram, Ati 64 megs and running at 167 bus, firmware 4.3.?
I bought a Mac 1.0 ghtz dual processor ( for £8.00, too good to miss and with a 7 day warranty ), to give me a little extra speed. According to all I have read it should be just a matter of removing the old and inserting the new. Not so!
After inserting the DP and before booting I unscrewed the heat sink and checked for contact between the heat sink face and the processor. Two white contacts showed.
I booted the comp and got a kernel attack. Switched off and rechecked the processor all appeared well.
Rebooted only this time ( and several subsequent attempts ) all I got was 20 seconds of nothing and then the fan went into overdrive.( I have never heard the fan go into overdrive, this comp runs very cool, idle 22 C and never more than 29 C at its hottest ).
During the 20 seconds of nothing the screen shows a " no signal " so I am assuming the MB isn't getting power. There isn't time for the processor to heat up to bring the fan on so its got me stumped.
I put the 1.25 back in and the comp boots up perfectly.
I would appreciate any help .
cheers,
Eddie.

PS. The power supply is an ATX 350amp which I hooked up a couple of years ago after the original Mac PSU stopped working. Therefore the White 25 amp isn't available. Possible cause?

666sheep said:

Check if there any bent pins on CPU daughtercard connector. Since 1.0 DP and 1.25 single use 167 MHz bus, swap should be plug & play. Fans will blast at full speed when unrecoverable hardware problem is detected during POST.
Anyways it's problem with your new CPU.

Click to expand...

Thank you for your reply and the fan tip.
The pins were the first thing I looked for when it wouldn't boot. They're all straight.
I got a message back from the seller who said they didn't think a dual would work on a single motherboard. Shows you how much they know.
I get my money back when I return the item.
Also no gong at start up.

Nameci said:

I would recommend the dual 1.42 or dual 1.25 G4 not the dual 1.0GHz. I have done swap from single 1.25 to dual 1.42 and it worked well.

Click to expand...

Nameci,

Oh! that one could afford such treasures. This is the UK not America. Either of the two cpu's would cost an arm and a leg. And when the worth of my G4 is approx US $40.00 the change over isn't feasible.

Zotaccian said:

Have you tried reseting SMU after the swap? You might try reseting Pram also if you get the machine to show picture. There was also dual 1ghz model with 133mhz fsb but I assume you know what you have.

Click to expand...

Re the 133 version. I have looked at them and they appear different in as much as the HSF and the cpu are all one piece . So I think I have the 167 version.
I haven't tried the SMU as the comp is running perfectly with the 1.25 SP. I have reset the Pram.
I did notice one thing when inserting the DP. When I insert the SP it just drops in, where as the DP has to be played with to get it to seat.
I have checked the DP with a magnifying glass and nothing looks burnt, swollen etc. And both cpu's are the same colour. I had read where one will/can be darker than the other.

Zotaccian said:

OK, I was just thinking that if you are trying to put DP 1.0GHz FSB 133Mhz CPU to a 167MHz motherboard you are actually overclocking the CPU's and they might not take it. Multiplier is set from the CPU card and FSB by the board. This would been a logical explanation why it does not work.

Reseting SMU and maybe PRAM would probably be recommended since you are installing totally different type of CPU(s). PRAM & SMU resets fix many weird problems many times, once after software update I lost my iSight camera on my iMac G5, it was not listed on the system information, reseting SMU allowed OS X to detect it again.

Click to expand...

I think we can be assured that the DP is the 167 variety. It states it is on it.
i.e. KC2400LRN8PH..MPU 1GHZ DP.

And I think what you are guessing at is that the firmware on it is older than the newer 1.25/167?
So, if I insert the 1.0/167 and then reset the SMU it should boot up, Yes?

Ok. Gentlemen the time has come to call an end to this little saga.
I tried the C,C and P, R trick and there is no change. I have come to the conclusion that the 1.0 DP is crook, ( for our American friends that is Aussie for ********ed!.).

I thank you one and all for the assistance and help offered.

Eddie