Thursday, September 27, 2007

Slow Boot Process on Mac? Try Clearing PVRAM

I've been spending a lot of time this week imaging Macbook Pro's, and with many of them I have been wasting time waiting for them to boot. The boot times were painfully long, bringing up a serious concern on my part. These machines are not even a year old, and yet their boot times were concerning.

Well, after a while I thought I would just clear the PVRAM. What is the PVRAM, you ask? It's a system level RAM that stores the processes for BootX (Running the BootROM POST, identifying the kernel , initializing the environment, etc.). This is where the EFI bootloader sequence is run, and it will even set up a default boot volume. If the PVRAM becomes too bloated (as with any system), it will bog down and finally crash.

Clearing the PVRAM is very simple: You just hold down Command, Option, P, R, while booting, and wait for the computer to chime again. I usually let it chime at least twice, to be sure the RAM is completely clear. Once done, you will see a marked difference in your boot performance.

But that's not all! I returned home to see my wife's iMac experiencing a horrific situation. It seems the computer has been booting directly to Windows (she needed Windows installed for a work project). In order to select the Mac OS, she has needed to hold down the Option key. I tried installing rEFIt, but it failed to load. Why? Well, because it would seem that the PVRAM was completely full, and on the verge of crashing.

Avoiding the obvious and painful jokes about Windows setting up the Mac to crash, I cleared the PVRAM. The boot process worked like a charm, going straight to Mac. Tonight I will reinstall rEFIt so the boot process will be easier to manage between the operating systems, and all will be well.

Yet another side-effect of working in a mac lab with multiple OS'es, you get to learn fun, fundamental things about how the Mac works. ^_^

1 comment:

Kieran said...

Thanks :) I just tried this and the boot speed increased by loads. Also, not sure if it's just my imagination but the whole mac feels snappier, more like it was 2 years ago when I bought it. Great tip

--K