i would suspect the video card and possibly the hdd speed. you can run gpu-z to see how the 860M is handling the footage, and the free version of hdd tune in combination with windows resource monitor to find out if the hdd is able to keep up with the read speed. if those show the computer can handle the footage it might be a format/codec issue with the media and cs6...
The CPU seems adequate, and the GPU as well. The big problem is the slow HDD. It will be annoying for HD, and it's just not going to cut it for 4K. I would change the drive. If you have the money, install a big SSD. If not, at least a 7200rpm drive. Another possibility is to connect 2 external drives in RAID 0 via the USB3.
Bill and Ronin are correct your problem is the lousy transfer rate of a single 5400 RPM disk drive. Glancing over the specifications of the unit imply some models have an m.2 socket if that is available install a m.2 SSD (if the m.2 socket is 4lanes go for a Samsung XP941) and clone the hard drive to the SSD. Then remove the Hard drive and install a good SATA SSD in its place. Then tune your system getting rid of all unnecessary processes to give you maximum CPU cycles. You do know that you have to have AC power to the system to give you maximum performance as CPU, GPU and other functions all run at reduced power when you switch to battery. I have an ASUS G750 gaming notebook configured as I mentioned and it works like a charm. Also you may want to try to speed up your GPU, mine is running slow even with AC power and I have been able to clock the memory on my unit very safely to 6 Gb/s (GPU-Z shows 1500 MHz) while the default is 4 Gb/s (GPU-Z shows 1000 Mhz).
When you get all tuned up you should be able to run our Premiere Pro BenchMark (PPBM) and see what your results are. If you register you can view the Results Page. I just ran this on this laptop and here are my CS6 results
The H.264 timeline has several 4K clips in it. Now that timeline I cannot play without dropping frames. But it is an extremely complex 7-layer timeline and if I turn off the bottom layer at 1/4 resolution it will play without dropping any frames so there are no guarantees because we do not know your workflow since you have a slightly newer/faster processor that will help you. I am guessing that your GTX 860M has 1152 CUDA Cores and is apparently the Kepler chip, and we do know Acer installed 4 GB of video RAM, so that is also a plus.
...I agree with Bill....I have the same laptop as him and upgraded the memory and drives like he did to achieve good performance. You machine has a better CPU and GPU than ours. As I have seen my laptop go over 20 GB of system memory use on certain complex timelines, I would suggest adding more memory...16GB these days is a little marginal...Bill and I have 24GB and if you can max it out at 32GB, that would be the best. Whoops....just saw your specs and it says maximum memory is 16GB in two slots only.....I'm not sure if only 16GB will hamper 4K editing or not...you can monitor memory use with "task manager" to see if it maxes out, ( make sure your memory settings are correct in PPro "preferences" ).
If you have the M.2 slot , using the XP941 would be a HUGE speed improvement. PPro needs two separate drives ,( unless using the XP941 ), to work properly in most cases. Using Crucial M550 SSDs are a good choice...they offer similar performance to the Samsung 850 Pro series at a lower price. Any single spinning hard drive will be a bottleneck with 4K...and most other footage. A 5400rpm drive makes a good paperweight, or, missile to be hurled at your TV screen !! Some newer laptops offer various storage configurations....check and see what yours are. Again, just saw someone from Acer telling a customer that your M.2 slot is limited to SATA III speed and is NOT PCI. In that case, the high speed XP 941 would be out, and you would have to use an M.2 SATA III SSD in that slot AND a second SATA III SSD, ( 2.5 inch ) in the other slot. One to be a boot drive with Windows OS and pagefile and programs....the other with all media, project files, cache files, previews,etc. You can experiment putting cache files on boot drive,or, previews, too, because of the high transfer speed of the SATA III SSDs.
Check out B&H or New Egg for deals on those SSDs, being careful to get the EXACT correct size M.2 SATA SSD for your particular slot. Your performance should increase greatly.....the single spinning slow HDD is the root of all evil !!...banish it !!
Bill is also correct about safely overclocking the GPU to achieve better performance. I use the free "MSI Afterburner" utility to overclock the memory clock to 903MHz over the native frequency, bringing the total to 2907 MHz and I tweak the core clock just a little, up 30 MHz. When exporting a complex timeline with many CUDA accelerated effects, this overclock has reduced my exporting time as much as 25%. There is NO overheating....with a different program I could probably increase the memory clock even more,but, this is good enough.
One thing to note...Eric Bowen here on the forum has shown in his testing that the newer Creative Cloud versions of PPro are much better at handling 4K than CS6, or, other previous versions. I know I experienced a noticeable improvement with the newer version on other codecs as well.
Good Luck !
Thank you for the in depth response! So I exchanged the computer for an
Alienware with similar specs except it has a 7200 rpm hdd instead of the
5400 previous one as well as the gtx 970 instead of the previous 860. Is
that hdd fast enough for 4k editing or should I still upgrade to an ssd?.?
It is a little hard to say because there are many versions of 4K and we do not really know your intended workflow. I would try it and see if it works for you. You can always easily add an good SSD or two.