I have recently started preparing my older Mac Pro 4,1 (Early 2009) 8-Core Dual 2.26MHz for switching OS X from Snow Leopard 10.6.8 to El Capitan 10.11.6. I mainly use this machine for working in Adobe CS4 application suite, and now plan to use the machine for additional video editing in Final Cut and Garage Band audio in the new OS. I had a few questions on the memory I installed on this machine and hoping some of you might be able to shed some light on if I did the right thing: MEMORY ---------------- Thus far I have installed 48GB of new OWC brand RAM / 8GB matched DIMMS (3 per CPU keeping with the Tri-channel configuration for max efficiency) Snow Leopard verified all memory is installed correctly and it can "see" all the new RAM installed on Snow Leopard (48GB) and I verified 64bit kernel when booting appropriately to initialize. My main question is if this amount of RAM will be a noticeable improvement from the 12GB that I always had in the system previously? Thus far after the RAM installation I am not seeing much (if any) of a difference in OS performance or apps I use even when booted to 64bit. Thinking Snow Leopard is not a true 64bit OS will El Capitan take better advantage of the additional memory as well as allow better access to that memory by my applications? ADOBE CS4 BUG ---------------------------- I am now also aware of the PS-CS4 memory bug so I understand that adding the additional memory (at 32GB or 48GB total) reduces memory allocation to the PS app even down farther to less than 3GB total. I now can only access 2.17GB or RAM where as the MAX PS would normally allow is just over 3GB with other memory configuration not totaling 32GB or 48GB, so the adding of more memory in this case was a detriment. I will post on this in another thread were appropriate to see if anyone has seen an improvement with this issue just by upgrading to a newer OS or even a direct fix in PS-CS4 but I suspect CS4 is just a dog I am still stuck with till I can afford to make a move there (CS6 maybe) and subscription based (CC) is not something I'm interested in.