With the introduction of OSX 10.3, Apple demands JEDEC compatible RAM. How did I learn this? While updating a friend's computer to OSX 10.3, I encountered a new phenomenon for me, the disappearing screen. Let me tell you the story...
Bob has an iMac G3, which according to Apple is compatible with OSX 10.3. However when we tried to install 10.3, we received a message asking us to upgrade the firmware, a message that is typical for Apple upgrades. To update the firmware, you go to Apple's firmware list, and download the upgrade for your model, then run the installer, turn off the computer, and start it up while holding the programmer's key, a small button with a carat symbol. You hear a long chime, and the firmware is updated.
However, due to a little-known problem, Bob's firmware update crashed his video....the screen died, although we could hear the computer starting up and spinning the CD. There was no way to access the open firmware settings or the console. Had the firmware update crashed? Did we permanently damage the boot ROM? No, the answer was both simpler and more complex.
I swapped the hard drive into another iMac, and it booted correctly, displaying a message, "Your firmware update is complete!" - seemed like a good sign. Next I swapped the RAM from the working iMac into Bob's iMac. Now it started up with the normal tone, then emitted three beeps and stopped working. I went a step further and dug out some RAM sticks I had lying around. After trying a couple, I found one that worked. Bob's iMac started up correctly, booted his hard drive and the monitor. Soon after that I found this document on Apple's website:
Firmware Update: Firmware Updates 4.1.7 and Later May Disable Out-of-Spec Third-Party RAM
http://docs.info.apple.com/article.html?artnum=60839
So remember team:
"When purchasing RAM modules for use in Macintosh computers, make sure that they conform to the JEDEC specification."
Otherwise you may face the blank screen of death!
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