So basically I have 16GB of DDR3 RAM in my Late 2013 27" 3.2GHz iMac. It's worked great up until just recently. I seem to run out of memory very quickly, even when I am not running much, or anything at all (except background programs, but they don't take up much memory). Just now I restarted my computer then I left to go to the store; I was gone for about 30 minutes and there was nothing running while I was gone except background programs and it's showing I have less than 10MB Free. It's bothering the hell out of me because I had W8 Bootcamped in but I restored my HDD because I needed more space for Windows (just for gaming), and this memory thing, which I thought a clean restore would fix, but apparently not. My Mac recognizes that there is 16GB installed when I click "About this Mac" or go to System Information, but when I run memtest to see my memory and how it's allocated, it looks like 8 GB of my RAM is not in use if I read this correctly. This is what memtest says (I am running it right now and it's not done but it looks like it's only recognizing 8GB. Memtest version 4.22 (64-bit) Copyright (C) 2004 Charles Cazabon Copyright (C) 2004-2008 Tony Scaminaci (Macintosh port) Licensed under the GNU General Public License version 2 only Mac OS X 10.9.4 (13E28) running in multiuser mode Memory Page Size: 4096 System has 4 Intel core(s) with SSE Requested memory: 8555MB (8971374592 bytes) Available memory: 8555MB (8971374592 bytes) Allocated memory: 8555MB (8971374592 bytes) at local address 0x0000000101000000 Attempting memory lock... locked successfully Partitioning memory into 2 comparison buffers... Buffer A: 4277MB (4485687296 bytes) starts at local address 0x0000000101000000 Buffer B: 4277MB (4485687296 bytes) starts at local address 0x000000020c5e2800 Running 1 test sequence... (CTRL-C to quit) Test sequence 1 of 1: Running tests on full 8555MB region... Stuck Address : ok Linear PRN : ok Running comparison tests using 4277MB buffers... Random Value : ok Compare XOR : ok Compare SUB : ok Compare MUL : ok Compare DIV : ok Compare OR : ok Compare AND : ok Sequential Increment: ok Solid Bits : ok Block Sequential : setting 111 of 256 Do you think if I unistalled the RAM and then Reinstalled it, it might just reset this? I tried resetting the PRAM too just to see if that might help, no dice. I am having a little bit of trouble installing W8 but I had a few months where I couldn't install Windows because these Haswell processors are so finicky. But W8 loads much easier than W7, so I have had more luck with that. Last time I just ran the Boot Camp Assistant and it worked fine, this time it wouldn't install on the Bootcamp partition. I tried formatting it in the Windows Setup and that was a no go, I also tried formatting it in Mac OS X to NTFS (I have a driver for NTFS formatting and reading). Still no go. Anyways I am more concerned with this RAM stuff because I have been thinking about getting 2x8GB sticks and upgrading to 24GB but if it's not going to use it properly, then it's kind of pointless. Any ideas? ANY help would be appreciated as this is starting to drive me crazy. Even with 8GB my computer should not be dropping to less than 100MB of free RAM, especially if all I am running is Safari (with 1 or two tabs). Sometimes I have a ton of stuff open in which case I would expect more RAM to be used. But I am barely using anything at all. I have to free up my memory using an app like every 10 minutes. So yeah is there a way to reallocate RAM, and does anyone know how this might have happened? I thought it might have something to do with VMWare and Windows 8 installed on that because I allocate 8GB for that (but I would assume it only uses that 8GB only if it's running, otherwise it would be kind of pointless). I don't know how my RAM will show up on Windows (if it will allow me to use all 16GB or not). But Mac OS X shouldn't have this problem whatsoever.