SOLVED: iMac 27'' (Late 2009) Poor Performance and Flash Issues w/ SOLUTION

They are roughly analogous to the instructions outlined in the Technician Guide—formerly called the Service Manual—for the iMac 27 inch (Late 2009) product family, and are similar generally to those in an applicable technical note for iMac and Mac mini products which use an intel processor.

The actual instructions from the guide are these for resetting Parameter RAM:

• shut down the computer.
• find the ⌘, ⌥, P, and R keys. If the keyboard does not have an ⌥ (option) key, use the Alt key.
• pres and hold the power button.
• immediately press and hold ⌘-⌥-P-R keys combination. You must do so before the gray screen appears.
• continue to press these keys until the computer restarts, and you hear the startup chime a second
• release the keys

And these, for resetting the System Management Controller:

• from  menu, choose Shut Down or hold the power button for ten or so seconds until the unit powers off.
• unplug all cables from computer including power cord
• wait at least 15 seconds: SMC reset occurs automatically once an iMac has been unplugged from AC power source for several seconds.
• plug power cord back in, making sure power button is not being pressed
• press power button on back to start up computer

I and most technicians I know have always waited for four startup tones to insure a proper PRAM reset: this goes back to the days of OS 6. As you can see, his instruction steps to do both in a single set are a hybrid of Apple's instruction set to achieve each reset.