Any idea why two 1GB RAM sticks show as 1GB total in my PowerMac G5?

[alexreich]

So, I was fooling around with a friend at his house looking at his old computer stuff. We were looking for things like RAM, wireless cards, etc to put in my PMG5. My friend found two RAM sticks, and they looked to be compatible with my system, so we thought we'd try them out in my G5.

The RAM configuration of my computer before any changes was:
Slot 1 - 512MB
Slot 2 - 512MB
Slot 3 - 256MB
Slot 4 - 256MB

Making 1.5GB total.

After removing the two 256MB sticks, and replacing them with both of the 1GB sticks, my RAM configuration is as such:
Slot 1 - 1GB
Slot 2 - 1GB
Slot 3 - 512MB
Slot 4 - 512MB

Which should have made a total of 3GB.

After carefully placing the RAM in, I closed the side panel of my G5 and powered it on. It seemed pretty snappy and responsive after bootup, so I assumed everything was swell. Just for the hell of it, I opened About this Mac, and it only shows 2GB RAM.

Confused, I opened the System Profiler and checked the Memory, and according to my G5 I have four 512MB RAM sticks installed.

Any idea on why the RAM is showing incorrectly?

I have attached these images to show y'all what I'm seeing...

 

[Intell]

They are high density ram sticks. PPC Macs are not compatible with high density ram and because of this can only use half of the ram.

 

[Lil Chillbil]

heres an idea mabye the ram is bad

but try booting it up with only the two gig sticks in it

 

[alexreich]

heres an idea mabye the ram is bad

but try booting it up with only the two gig sticks in it

Did that.

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They are high density ram sticks. PPC Macs are not compatible with high density ram and because of this can only use half of the ram.

Ahh, thank you for the information. After doing a bit of Googling on the RAM, someone with an iMac G5 had them show as 512MB sticks as well, and someone said the same thing you did on that thread.

 

[California]

Did that.

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Ahh, thank you for the information. After doing a bit of Googling on the RAM, someone with an iMac G5 had them show as 512MB sticks as well, and someone said the same thing you did on that thread.

Thos PMG5s are very picky with ram. You are lucky those sticks even registered at all; in fact I've never seen this happen before. They are matching pairs, right?

One note on the pMG5s on ram. All your ram will run only as fast as your slowest sticks. I can't remember how this works but that was what I learned about my pre Tiger PMG5s.