2009 mac pro: RAM not being recognized

[Ravich]

I got some RAM in the mail today. x2 4GB modules from OWC. Previously my memory setup was x2 4GB modules from OWC, and x6 of the 1GB modules that came with the mac.

For some reason, after I installed the new RAM, one of the older 4GB modules is no longer being recognized. The top right slot is listed as empty when I check "about this mac"

I already tried taking the RAM out and putting it back in....

Any advice?

Edit: I tried swapping the placement of the old OWC modules with the new OWC modules and now it's reading everything properly. Ugh. What the hell was that about?

 

[GGJstudios]

Edit: I tried swapping the placement of the old OWC modules with the new OWC modules and now it's reading everything properly. Ugh. What the hell was that about?

Could be a case of a module not seated properly. It's quite common.