Crazy problem with two G4's

Crazy Deal, I have two G4 desktops a 867mhz Quicksilver and a 733mhz Giga well I have a powerlogix upgrade 1.6mhz running in the 733mhz and it is great. My problem is I decided to put the upgrade in the 867mhz and return the 733mhz chip to it 733mhz mac. Well after I did this the 733 would do the push button for start and light was on when pushed and went off, the red led on the motherboard stays on and I hear a click of hard drive and power supply come on but the mac doesn't respond to keyboard commands, nothing on the screen just black, will not start with OS disks, reset pram button. NOTHING, but the 867 mac is running the powerlogix 1.6 upgrade just fine. So I thought I'll put the upgrade back in the 733 and see what happens and now it is running fine in the 733 again but now my 867 machine is acting like the 733 did before as in not responding to keyboard commands or start up OS disks? I did this because I was going to give the 733 mac to my nephew to replace his "Yikes" 400mhz and he did not need the bigger upgrade. Batteries are new, hard drives fine, ram and video cards have been reseated and fine , Power supplies are working fine. I have tried to start each in Target disk and they do not show up, and the keyboards don't work like the ports (USB,Firewire) are not working. Help me Please!