1.8 GHz CPU's on a 2.0 GHz Logic Board

I took apart a broken 1.8 GHz Powermac, and built all the parts on a 2 GHz Logic Board.
Now the thing won't start up, the screen stays totally black, I hear the HDD spin up, the superdrive starts up, the fans start up at low speed, so I guessed the logic board is ok.
What I did so far, apart from spending hours searching the fora was, replace the RAM, replace the videocard for a brand new one, swap the hdd, rested the pmu, couldn't reset the PRAM 'cause the keyboard doesn't work, still the result at boot stays the same.
So I was wondering, maybe it isn't possible to place the 1.8 GHz CPU's on a 2.0 GHz board, can anyone tell me ?

I think you answered your own question based on the amount of work you did and the results. I'm not an expert on the Powermac nor do I own one, however, I have seen other posts similar to yours and to my knowledge, no one has successfully done a "brain" transplant.

In a nutshell, there are too many variables and too much that can wrong when trying to swap a logic board from one model to a different one.

Regards.

chscag said:

In a nutshell, there are too many variables and too much that can wrong when trying to swap a logic board from one model to a different one.

Regards.

Click to expand...

Great post! This is exactly what I was thinking when I read this post earlier today.

The main issue or question from the OP seems to be "can dual 1.8ghz processors work on a 2.0 ghz board" (which I assume means that the motherboard originally had dual 2.0ghz processors on it)...I don't think that there necessarily is such a specific thing as a "2.0ghz motherboard".

Let's assume that if someone starts with a Powermac G5 motherboard that originally had dual 2.0ghz processors on it...and now someone wants to install dual 1.8ghz processors onto this motherboard. Maybe this will work, maybe it won't.

One thing that REALLY complicates things is...Apple released FOUR different versions of the Powermac G5 dual 1.8ghz...and Apple released THREE different versions of the Powermac G5 2.0ghz. So there are a lot of different combinations that could be made (motherboard & processors)...and maybe some of the combinations may be compatible...and some combinations may not.

I know that all of these motherboards ARE NOT the same...since some have PCI expansion slots, and some have PCI expansion slots. Some have 4 ram expansion slots & some have 8 ram expansion slots. So other things on these motherboards may be different as well.

Just for discussion sake...let's assume all combinations are compatible (motherboard & dual processor combinations). The we get into compatible ram & video card issues.

So with this project...there could be multiple issues causing the computer not to boot properly. And even if one issue is solved, a 2nd or 3rd issue could be causing the boot problems. Since we cannot with 100% confidence determine what is & what isn't compatible...it hard to say what parts are working properly & what isn't.

- Nick

I take it he is talking about a Power Mac G5? If so, agreed with both replies. Also what video card did you purchase? PC Video cards will not work on Macs unless they are flashed with a Mac ROM.

As others suggest, did yiou install Mac compatible memory and graphics card as PC compatibles will not work. This means you have to buy from a Mac dealer/reseller/online seller as PC shop memory and graphics just won't work despite what the sales folk may have told you.