Ok, can anyone answer this one? I've a mid 2011 iMac with a 2tb internal hard drive installed by an Apple engineer in mid 2015. I've the maximum 16 gig of ram, newly installed in mid 2015. I have 1 X 1tb external hard drive attached and also 1 X 500 gig external hardrive attached. Both external hard drives are being fed by time machine. My system shows masses of room on both the internal and 1tb external hard drive (although, admittedly, the 500 gig external hard drive is almost full). I am running El Capitan as my O/S and all updates are installed. My Logic Pro 9 is running at 64 bit (and the required 32 bit bridge is present). I have Native Instruments Komplete 10 Ultimate as a 3rd party plugin ( new in mid 2015) as well as Izotope Ozone 7 (bought in mid 2015 and up to date), Izotope Neutron (bought this week - and it's fantastic!), and FX Expansion's BFD Eco drum / percussion plugin (2012 and up to date). My puzzle is this: I have a project with data on 60 channels (due to my multing parts: most channels only have bits of data on). All software channels have been bounced / converted into audio tracks (to save on CPU). I have my bit rate set to the highest and my buffer rate set to "smallest" yet I am still getting massive CPU readings up into the red and little is seemingly being sent out to the iMac hard drive to take the strain off the CPU. I've tried it every which way round but no change! Firstly: why am I getting such high CPU readings when there isn't really that much information recorded and, what there is has been converted to audio? And, secondly, despite my bit rate and buffer settings: why am I not seeing more distribution out from the CPU onto the Hard Drive to share the load? By the way, the distribution between the CPU and the Hard Drive appears not to alter no matter what variation of Bit Rate / Buffer settings I use: high or low, small or big. There is a fair bit of automation applied across the project but not any more than on other projects I have where I don't experience this problem. I also have 7 or 8 aux busses set up and 10 to 12 sub mix aux's set up (although the problem pre-dates my setting up these sub mix aux's). I am finding it difficult to play the project all the way through as every so often on any given time I have the project playing I get a freeze / stop and the dreaded "system not able to process the data fast enough" pop up. Any suggestions? Cheers: Chris.