Mac Pro 2009 install RAM

[DenBeke]

I thought that installing ram in a Mac Pro couldn't be so hard, until I started the Mac Pro...

I have 4x4GB and 4x2GB, So at first I did:

1 -> 2GB
2 -> 2GB
3 -> 4GB
4 -> 4GB

5 -> 2GB
6 -> 2GB
7 -> 4GB
8 -> 4GB

But the Mac recognized only 20GB ram.
After that I tried another setup:

1 -> 2GB
2 -> 2GB
3 -> 2GB
4 -> 2GB

5 -> 4GB
6 -> 4GB
7 -> 4GB
8 -> 4GB

Same problem, 20GB ram found.

I thought that you only had to pair the ram of the same size on 1&2, 3&4, 5&6 and 7&8.
But apparently I'm doing something wrong with the ram sizes.

Anyone who can help me out?

 

[azentropy]

Sounds like either

a) you have some bad ram
b) you don't have the ram size you think you do
c) you have bad slots.

Do "About this Mac" -> More Info... and then click on the Memory Tab to see which slots are not registering or are listing different sizes than you think they should be.

 

[Studio K]

Though it is nice to be able to use the RAM you've got (and save some money as well), it is probably best to use matching sets of RAM (matching size at least). I don't know if the brand of RAM needs to match, though your chances of success are greater if ALL of your RAM is the same manufacturer AND size.

If it's 24GB you are after, then you could purchase 2 more sticks of 4GB RAM from the same manufacturer as your other 4 sticks.
You could then install the ram in sets of three to take advantage of triple-channel memory. Like this:

1 -> 4GB
2 -> 4GB
3 -> 4GB
4 -> empty

5 -> 4GB
6 -> 4GB
7 -> 4GB
8 -> empty

 

[DenBeke]

I've bought the Mac second hand.
The person who delivered it to me said that apparently after all one ram stick was broken. It worked a week before, when he advertised for his Mac

But I saw that the man cleaned the inside of his Mac, so I think he misplaced the ram after he cleaned the Mac. Since before the ram worked.

 

[Studio K]

I've bought the Mac second hand.
The person who delivered it to me said that apparently after all one ram stick was broken. It worked a week before, when he advertised for his Mac

But I saw that the man cleaned the inside of his Mac, so I think he misplaced the ram after he cleaned the Mac. Since before the ram worked.

Which Ram stick is broken? IS it a 2GB stick or 4?

 

[flowrider]

It appears to me that one of the 4GB sticks is not working. And it's apparently one of the one's you put in slot 4 or 8. To find out for sure go to "About This Mac" located under the Apple on the left side of the menu bar. Click on it, click on "More Info" Click on Memory. You will get a graphical pict like the one attached. This will tell you which slots are working.

From my experience, RAM installed in slots 4 or 8 will not work unless the sticks installed in slots 3 or 7 are the same size and are working.

The Intel CPU is a three channel memory processor and slots 1,2,5 and 6 are independent. Slots 3 and 4 and slots 7 and 8 share a channel. Optimal performance is obtained by leaving slots 4 and 8 MT. Also, it is best if all your Ram is the same speed and from the same manufacturer.

Lou

 

[DenBeke]

It appears to me that one of the 4GB sticks is not working.

You were right!
I've swapped a stick and so I found out that it's really broken.

 

[flowrider]

^^^^Glad I could help

Lou