I have purchased a dual 1.25Ghz processor and need to know if I have to change jumpers or anything on the motherboard to make it work. I have inserted it and when I turn it on I don't hear the familiar startup sound and within 30 seconds the power fan starts up. Can anyone tell me what to do or if this processor is bad and how to check.

Might help if you tell us what G4 machine you have and what upgrade you purchased.

Also, did you follow the instructions in the box/on the manufacturer's web site regarding installation?

I asked a similar question to Currawong in your identical thread elsewhere here. This what I had to say there:

I suspect the OP has bought the CPU daughter card from a newer G4 and put it in an older one, where it wont work.

I got some details from the OP. Basically the model, M8570, is an MDD of unknown speed.

Apple 820-1497-A is a single 1.0GHz or 1.25Ghz unit.

While I couldn't get a decent search result for this: Apple 820-1452-A, it appears that it is, in fact, a dual 1.25GHz unit. The only result I could get on this was some poor french guy who is having exactly the same issue as the OP.

Ideas anyone?

Reset CUDA? This needs to be done with CPU upgrades.

JB

What was the speed of the original CPU that you are replacing? Just to make certain of a couple of things:
1. It definitely has 167MHz system bus?
2. 1GHz MDD's used PC2100 SDRAM, faster dual CPU MDD's had to use faster PC2700 RAM.

EDIT: I referred back to your other similar thread so I guess you can forget the above. It really does make it easier keeping it all together.
Also, have you checked out this thread from macosxhints? Or this one?

Suggestions were:

1. Poorly seated CPU. Is it actually installed and seated properly?

2. Have you reset the PMU? (Byrd suggested this; you didn't get back to us) The suggestion was reset the PMU, leave the computer unplugged for 24 hours and try booting then. (some voodoo about making sure the PMU is really reset)

If these suggestions haver failed, I assume you have tried the original CPU and that that still works? If it does your logicboard is good and the CPU daughterboard seems likely to be bad. Have you checked the CPU daughterboard for signs that someone has attempted overclocking it? (desoldered surface mount resistors or signs that these may have been de/re soldered?) If this has been performed by an inexperienced person and both cores are not set for the same speed the computer will not boot. Alternatively it may have been destroyed in the process.

I'm guessing you bought it from ebay? This will not be what you want to hear but did the vendor have a good feedback rating? Does he/she sell Mac equipment generally? (ever even?) Were they an established eBay seller or are they a newbie? If it was an eBay newbie it seems possible that someone just sold you their dead CPU. "It was working when I shipped it".