Thanks for the memory

This morning, I received the 2GB RAM kit that I ordered, and I’ve just installed it in my iMac. Now – those of you that have been around for a while (you know who you are) – will remember back in 2005 when I got myself worked up into a frenzy the last time I installed new RAM into my machine. I did have just the 512MB that came pre-installed, so when I found out that optimal performance was to be gained from having two matching RAM modules I bought another one to boost things to 1GB and hopefully unlock the wonders of the mythical “128-bit pipeline”.

Now when I had just 512MB, Terminal reported this:
phil-laceys-imac-g5:~ Phil$ ioreg -p IODeviceTree -n memory -S | grep ram-
| “ram-layout-architecture” = <00000002>
| “ram-bus-width” = <00000040>

Then, when I went up to 1GB, I got this:
phil-laceys-imac-g5:~ Phil$ ioreg -p IODeviceTree -n memory -S | grep ram-
| “ram-layout-architecture” = <00000002>
| “ram-bus-width” = <00000080>

At the time, I really couldn’t work out whether this meant I was using the 128-bit pipe or not – the bus width had changed, but not the architecture value. But more RAM is always good regardless, so I was happy. Things nipped along quite nicely.

So, for the sake of consistency, I tried the terminal report again now I have two matched 1GB sticks in the iMac – just to see what it would say. So we now have:
phil-laceys-imac-g5:~ Phil$ ioreg -p IODeviceTree -n memory -S | grep ram-
| “ram-layout-architecture” = <00000001>
| “ram-bus-width” = <00000080>

Which is different yet again. However, this Apple knowledgebase article would seem to suggest I am now at the very pinnacle of G5 iMac memory nirvana – 2GB of RAM, in a perfectly matched pair, running on the 128-bit pipeline.

That, my friends, is as good as it gets.