Does my iMac A1076 G5 have a 1.8 or 2.0 ghz processor

Was wondering if there was a way to determine which model A1076 I own, the 1.8 or the 2.0 ghz model without having to turn the machine on? The reason being because the imac doesn't turn on. I press the power button and the machine will start up but quickly turns off, the length of time the machine will stay booted varies from 1-60 seconds. I believe the machine needs a new power supply.

So anyway once again is there anyway to determine which processor the computer has without turning it on?

Thank you in advance for any information you can provide for me on this issue.