I have a Mac Pro 4,1 (Dual 2.66Ghz, 6GB Ram). I want to increase the RAM, possibly adding 8GB to my existing 6GB. The RAM slots are used as follows:

  • SLOT1: 1GB
  • SLOT2: 1GB
  • SLOT3: 1GB
  • SLOT5: 1GB
  • SLOT6: 1GB
  • SLOT7: 1GB

What are my options without removing the RAM that I already have?

2 Answers 2


I think you can put more than 16Gb in your Mac Pro. Apple tends to not put the real number in. Check this page:


RAM prices are ridiculously low these days, better put as much as your budget allows you. You can have 32 Gb for 320$ US, or 16 Gb for 165$.

And since you have 1 Gb modules, you should put them in the slots, like 3 & 7, or 4 & 8, if you intend to use them. i.e.: put your biggest modules in the first slots, and then go down in size the further you go. And RAM modules have to be similar for alternating slot positions, i.e. 1 & 5, 2 & 6, etc...

If I may ask, what is your goal with putting more RAM in your machine?

  • Goal = To increase performance of Lightroom and Photoshop (64-bit apps) by being able to shove more into RAM (Professional Photography) Sep 13, 2011 at 2:24
  • The link in the answer above is to a company called Other World Computing, or OWC. Contact their sales or technical support and they will tell you exactly what your options are with upgrading RAM on your specific model of Mac. They can give you an authoritative answer.
    – user9290
    Sep 13, 2011 at 4:06

It looks (according to my copy of Mactracker) that your max RAM is: 16 GB for a quad-core or 32 GB for an octo-core.

You're already using six gigs, so if you have a quad-core machine you can put in up to ten more. They don't make five-gig sticks that I know of, so four gig sticks would be your maximum, for a total of 14 GB. If you have an 8-core machine, you can put in up to 26 more gigs. If you can find 12-gig sticks (which I doubt), you can put an additional 24 gigs in, but it is more likely that you can put two 8-gig sticks in for sixteen more gigs. This will bring you to 20 GB or (more likely) 22 GB of total RAM.

  • My machine is a custom-build, consisting of 2X quad-core 2.66Ghz Xeons. I think I am still limited to 16GB however. So I can put a 4GB in both SLOT4 and SLOT8? Sep 13, 2011 at 0:19
  • Yes, but I would put the largest modules first, then in decreasing order of size, like I mentionned before. As for maximum performance, you should put the maximum amount of RAM you can afford, even if it means removing all the modules you have in it already. 64-bit apps will make use of the extra RAM. 32 Gb is a pretty nice amount for PS CS5, will barely touch the HD when it will need to scratch.
    – Fred
    Oct 11, 2011 at 20:30

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