Thursday, March 17, 2005

How to plug in an Apple computer -- first the AC, then the computer?!

Wow. I'd never have imagined this one! This business of embedding computers throughout complex hardware has some substantial limitations. Hmm. I wonder how far that meme extends.

Apple machines are infamous for controlling hardware via software. My PC has a simple thermal sensor that controls fan speeds, but on a Mac fan speed is the responsibility of low level OS code. My PC does simple error checking on memory at the hardware level, the Mac expects error free memory. PCs power supplies are brain dead, the Mac has a 'power management unit' with its own OS and firmware.

Which approach is better? I'm sure there are good arguments for Apple's approach (not to mention it makes cloning very hard ...), but my experience is 'stupid is better'.

The story of the PMU is illustrative. As reported in MacInTouch (from Desktop and Portable Systems: A Guide to Supporting, Servicing and Troubleshooting Apple Computers):
While skimming the book, we noted some interesting tips about power management, including the non-obvious, but apparently critical, issue of exactly how you connect an AC adapter:

* The PMU [power management unit] is a computer within a computer. It has memory, software, firmware, I/O, two crystals, and a CPU.

* If you connect the AC power adapter to the computer before you connect the adapter to an electrical outlet, you can make the Power Manager software unusable. Symptoms of issues with the Power Manager software include startup problems and the inability to shut down the computer (the computer restarts spontaneously after shutdown.)
Oookaaay. A few comments:

1. Ever wonder whether you should connect your iPod to the charging cable and then the cable to the firewire port - or vice-versa? Given the above, this may a choice between devil or the deep blue sea. Do it one way and mess up the iPod, the other and mess up the iBook!

2. Generally one tends to do the "right" thing -- plug an AC adapter into the wall, then connect it to the portable (iBook, etc). But what about people who like to power up via a surge suppressor? That used to be common practice. I wonder what that does?! What if there's a power failure and the power comes back on again? What if you accidentally disconnect the AC adapter and plug it back in?!

3. Wouldn't it be nice if Apple documented this somewhere?

4. Clearly, computers aren't ready for use by normal people.

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