Hardware: iMac8,1
Memory: 6GB DDR2 SDRAM (2gb in slot 1, 4gb in slot 0)
OS: 10.6.8

Problem: On startup, computer would beep three times, pause, then repeat the three beep pattern. The one time that it did restart, I ran verify disc and it found errors.

Solution:
Boot from a CD -> Beeps
Re-seat the RAM. -> no change
Take out one RAM stick -> was able to boot and run disc utility repair
Blew out the RAM socket with compressed air.
Re-seat both RAM sticks in reverse order (2gb in slot 0, 4gb in slot 1). -> Boot went fine.

So, now I don’t know if it is a memory problem or a directory error. I skipped too many steps while troubleshooting. After several reboots, the problem hasn’t come back. We’ll have to wait and see.

Studio 1 and Studio 2 are getting 4 GB more memory.

The only complication that I had installing it was determining which slots should be used. Generally, computers like memory to be installed in pairs. Our Mac Pro machines have two memory cards (A and B) with four slots each (1, 2, 3, 4). They were shipped with 2GB installed.  That was four 512k modules installed in A1, A2, B1, and B2.

I didn’t know how to pair the modules so my first attempt was to keep the 512k modules where they were and add the new 2GB modules to A3 and B3. This resulting in the computer not even seeing the new modules.

Second attempt was to put the new 2GB modules in A1 and B1, then put the 512k modules in A2, A3 and B2 and B3.  This resulted in the computer only seeing 2.5 GB of memory (A1 and A3).  Mysterious.

By the way, I’m check total memory in the “About This Mac” under the Apple menu.  Then, if you click on “More Info,” it opens up the system profiler application.  Check out the “memory” section for details.

Third attempt was to put the two new 2GB modules in A1 and A2 and the existing 512k modules in A3, A4, B1 and B2.  This was the correct arrangement. The computer shows 6GB of RAM and the system profiler correctly lists all the modules.