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Fixit 24. Zap the Parameter RAM > Really Zap the PRAM: Use TechTool

Really Zap the PRAM: Use TechTool

Unfortunately, the standard method (Command-Option-P-R) of zapping the PRAM does not reliably zap all the PRAM data. If the remaining unzapped portion of the PRAM is corrupted, the previous zapping of the PRAM will not fix the problem. This seems to happen particularly with the PRAM data that affects the SCSI and serial ports. For example, you may find that, even after zapping the PRAM, you cannot access external SCSI devices. Or it may be that when you try to use your modem you get an error message that says the serial port is "in use." In these cases, you need to completely zap your PRAM.

Removing the Mac's battery or using the Cuda/PMU button will completely zap (and then some), but there's an easier way: use a software utility. Several utilities completely zap, but TechTool is my first choice. (Yes, this is the same utility used to completely rebuild the desktop, as described in Fix-It #8.) As an added bonus, TechTool will save your PRAM settings before you zap, allowing you to restore them when you are done. TechTool Pro also has these same features. Here's what to do, using TechTool:


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