Adding memory to MacPro - which slots?


I have a Mac Pro 3,1 (2008) that currently has all slots filled with 1GB DIMMs. I am about to put a couple of 4GB sticks in it and am wondering if there is any advantage in one spot over another.

I’m aware they have to go in pairs and that the pairs go together, but not sure if there’s anything else I need to keep in mind, like whether they’re best in the top or bottom riser or something.

Any knowledge on this would be appreciated, thanks!


Pretty sure as long as you follow the order of the top/bottom risers and slots, there’s no inherent performance advantage over putting DIMMs in one pair of slots over another.

I wouldn’t have thought so, anyway.


Guide for MacPro 3.1 RAM


Yeah, likewise. I’ve been having a bit of trouble with one of the risers - it keeps cutting in and out causing spontaneous restarts - so I’ll put them in the other one I think.


Are any of the the LEDs on the RAM risers showing red. Faulty RAM can cause restarts. Also you have to push “firmly” to seat the risers.

If you don’t have copy already here is a link to MacPro early 2008 Service Source


I haven’t checked recently, but I’ll do it before I start swapping memory out. The issue has been going on for a while and started happening in summer, so I thought it might be related to dust in the machine because it tends to go away after I give it a good blow out. I haven’t cleaned it recently, so I’ll do that when I open it up.

Thanks for the link to the service manual!