powermac g3 - mobo damaged?

Is is a rev A? If it is, put a Rev B mobo in it. The Rev A had a bad ATA controller chip. The Rev B fixed that.

To clarify, the Rev A had an IDE controller chip that had troubles with secondary hard drives. And it didn't kill drives either, just eat data.

The Rev B boards had a better controller that played nice with both primary and secondary drives.

Your motherboard is likely bad, though, if it kills drives.

So what happens with the bad harddrives besides the whining sounds? Do they boot at all? Do you get video output and what Mac OS do they have? Have you tried the bad harddrives in another machine?
A bad firewire module can stop your boots at the happy face, so try removing the firewire module from the motherboard and then boot from the CD.

the Rev B boards have a chip labeled "402" near the PCI bus, the Rev A doesn't have it anywhere (the only way I know to tell...)

yeah, and I'm not sure it being Rev A would make any difference...

What causes HD to be killed? Power spikes? Could that be a bad power supply?

I've had scsi cards that fried HDs before, so maybe a bad controller can be wonky.

Specifically the Rev B motherboard has a CMD-402 IDE controller and the Rev A motherboard have a lower numbered CMD IDE controller like a CMD-401 or CMD-400. The IDE controller on the Rev A boards have a tendency to eat data because of hardware bugs on the controller. At any rate, another way to tell at if you probably have a rev A board is if there are screw holes and a second connectors on the IDE and power cables for a second hard drive on the drive sled nearest the back. There is another drive sled nearer to the front that only has space for one drive on both revisions I would say that it would probably be a Rev A board because some Rev B boards shipped with only single hard drive drive sleds too. However no Rev A boards shipped with the dual drive sled.

it's a rev. a motherboard, the mobo is from 1998...

didn't have time to test the suggestions with the firewire ports though, but i will test it later that day.

thanks!

this is requesting an extra "arrrrrrr", although pirate's day is already passed by this year.

you were completely right with the firewire board. it's gone. forever... after removing it, the mac was booting successfully from the original os 8.6 cd without problems! however, the original hard drive is damaged, this is for sure. it spins up, then it clicks a couple of times, spins down, then spinning up again and the whole story starts from the beginning.

thanks a lot for your help and sharing your experience! h.a.n.d., chris

ps: next step -> testing another hard drive and hope that the b/w g3 doesn't eat it too...