Previous Gen i7 vs. current i5 for longevity

I thought the 2014 iMac 27 CPU choices were a Haswell 3.5Ghz i5-4690 or 4Ghz i7-4790K. The 2015 iMac 27 i5 choices are Skylake 3.2Ghz i5-6500 3.3Ghz i5-6600.

Clock-for-clock, Skylake is probably about 7% faster than Haswell. If you are talking about a 2014 iMac 27 with 4Ghz i7 vs a 2015 iMac 27 with a 3.2 or 3.3Ghz i5, from clock speed alone the i7 would be about 21-25% faster. Subtract about 7% for the i5 Skylake advantage. The i7 has a hyperthreading advantage in highly specific circumstances, but in general you won't see a huge difference.

You would probably be happy with either one. I've tested the hyperthreading feature on my 2013 and 2015 iMac 27 using a special utility (CPUSetter) to disable it. The benefit of the i7 hyperthreading is highly variable. When exporting from FCP X it's about 30% faster. It does nothing for Lightroom import/export. I haven't closely examined what Photoshop tasks it might help on.

Aside from possible the i7 vs i5 thermal differences, this area was improved on the i7 models between 2014 and 2015. In general I'd slightly recommend the 2015 i5 model simply because it's newer and you are unlikely to see a significant performance difference from hyperthreading given your workload. OTOH if the 2014 i7 was really 4Ghz, that is approx 18-20% faster than the i5 from clock speed alone. That is enough to notice a difference. OTOH when I use my wife's 2012 iMac with 3.2Ghz i7, it doesn't feel slow.

If I am mistaken about the 2014 i7 speed and there was a 3.3Ghz i7, then no question get the 2015 i5. If the 2014 you're considering is actually 4Ghz, then consider whether 18-20% CPU speed is worthwhile. This doesn't mean your tasks run that much faster, just the CPU portion. Either one would probably be fine. I doubt you'd see any thermal reliability issues from a 2014 4Ghz i7.

Make sure you get one with a retina screen. While there are sometimes some good deals on a 2013 non-retina iMac 27, the screen just isn't as good. Counter-intuitively, this makes a bigger difference for text than for graphics.

 

Yes, the top i7 for 2014 was a 4790K. And the top i7 for 2015 is the i7-6700K.

 

The feature that really distinguishes i7 from i5 is hyper threading. That's a software-dependent feature - either the OS/app uses it, or not. I'm not aware of any kind of trend in software development that suggests a move to greater use of hyper threading. Pretty much, the types of apps that use hyper threading today used it yesterday. OS X has been using it for years. So, it's not so much about future-proofing, but the kind of performance you can expect from it today.

 

While there may be isolated instances where you might benefit from hyper threading, (many open browser windows/tabs, perhaps), most of your usage does not. Check with the maker(s) of your sound recording app(s) - hyper threading is used when multiple tasks can be executed simultaneously. Most of what you do is more linear in nature - one thing after another (updating one item triggers the updating of the next). You may have very large open documents, but very little is done to them at any given moment. RAM is likely to be more important than the number of processor cores.

Note that hyper threading is a method for stretching the performance of a processor core - it really doesn't come into the fore until you've exhausted the number of cores in your processor. Many apps don't use more than a single core, so they wouldn't take advantage of hyper threading. All things being equal, having a two-core processor that hyper threads will be less effective than having a four-core processor that does not have to hyper thread.

 

Depending on the implementation of the program a two core hyperthreading cpu can have very good performance as long as the two threads are not competing for the same resources. https://en.wikipedia.org/wiki/Hyper-threading

 

If "bog down" means a visible spinning beachball cursor while the Word document is loading, it's possible Word/Pages is not taking advantage of background threads ( also known by the marketing name "Grand Central Dispatch" in the Apple world ); this problem will persist regardless of i5/i7 simply because the app isn't designed for better user performance. One key, as mentioned by other posters, is to investigate the apps you use and find out if they are designed to use background threads. Many apps do and others do not. Its implementation depends on many factors such as developer skills, time and its use isn't limited to known high-end CPU hogs. Figuring out ( assuming the developer doesn't disclose it ) if an app is designed for background threads is possible but patience and developer skill/tools are required ( although watching in Activity Monitor might give you some clue ). An Apple store visit might shed some light: launch Word on their machine ( possibly you can make your doc available via the web and open it on the store machine ). Good luck

 

As always with getting a (new) Mac or any pc, don't underestimate the gpu. Keep the cpu and gpu in balance. Don't get the entry level gpu, this will slow your mac down, especially in a few years when everything is more graphical.

The i5 would probably suit you fine, an i7 can really help with soundrecording, depending on the programs you use and how much tracks you record simultaneously.
You're already getting the ssd, so that's already good. A normal HD is really slow and will impact performance.

 

There are no "hyper-threaded apps" per se. Rather there are only multi-threaded apps, which may or may not benefit from hyperthreading. In general the programmer has little control over this. There is no hyperthreading API or special instruction set like with Quick Sync or AVX instructions. It just happens or doesn't -- totally up to the CPU.

Most apps are heavily multithreaded. Just opening Safari produces about 24 threads. However this does not automatically mean a hyper-threaded CPU will speed up Safari, since most of those threads are not in a runnable state, but waiting on I/O, or a synchronization event. However any app with multiple threads in a runnable state are potential candidates for hyper-threading.

The OS X thread dispatcher is hyper-thread aware and will often schedule a thread per physical core (rather than a thread per logical core) if it judges that more efficient. This is to reduce cache thrashing, and can be seen in Activity Monitor when every other logical core is scheduled.

While there are no "hyper-threaded apps" per se, developers can use various techniques to make their apps better behave on a hyper-threaded CPU. Intel has guidelines on this in their whitepaper "Developing Multithreaded Applications: A Platform Consistent Approach": https://www.google.com/url?sa=t&rct...=_PNWoHGsa3skn-LpZN2Ndg&bvm=bv.83339334,d.eXY

You would be happy with either the 2015 i5 iMac 27 or the 2014 i7 iMac 27. The retina screen was slightly improved in 2015 from a color standpoint. The 2014 4Ghz i7 is probably 18% faster from a CPU standpoint (not considering hyperthreading). Other factors such as hard drive configuration and GPU are also important. E.g, I wouldn't get an iMac with a plain spinning hard drive which was not either Fusion or SSD.

 

Hyper threading is much more about threads rather than tasks. Obviously multiple CPU taxing tasks benefit as well, since each task has at least one thread. But it is of much more significance what kind of application one is using. There'S no benefit from HT when using up to 4 single threading applications.
These days, well written applications create many threads for CPU heavy tasks, but there are still a ton of programs out there that use multi threading poorly or not at all.

 

The R9 M395 is pretty good. See spreadsheet with perf. tests we did in this post: http://forums.macrumors.com/threads...e-2013-imac-and-a-2015.1957498/#post-22594734

As a video editor I always get the fastest CPU but for general purpose use the M395 is OK. If you mean the M390 I don't have numbers on that. You would be happy with either imac. They are both great machines. The #1 thing is the retina display, and avoid a non-Fusion spinning drive, which you've already decided on.

 

I would probably choose the i5 (2015) iMac 5K. The performance will be roughly the same and I strongly believe both computers will work equally for your needs in 5 years time. But the newer one gets newer peripherals (the new keyboard and mouse) and the new DCI P3 screen with better colors. Also, not sure how noticeable is this, but the newer iMac has faster Fusion Drive/SSD speeds.

You won't see the performance difference between the two computers in real life, but you will see slightly better colors and the new keyboard is quite better in my opinion.

Just make sure you get either the larger Fusion Drive (in 2015 models, the 1Tb Fusion Drive has a smaller SSD portion, so choose the 2Tb one) or an SSD.

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Whatever you do in Pages, you will not see any difference between the i5 and the i7. I don't think Pages uses more than 4 threads, if that much. I'm not sure why your computer is bogged down, it could be the RAM, it could be something else entirely. But the difference between an i5 and an i7 is noticeable in multi-threaded apps that use more than 4 threads, and these are mainly rendering apps and video editing apps.

 

Hmm. A lot of compressed memory on that macbook. Now, Apple argues that compressed memory is far superior to the alternative-- swapping to disc-- but it does take CPU cycles to manage.

You could also look at Console.app and see how many bugs are flitting by, but interpreting these logs requires some experience.

 

Could be. I have an i5 imac 5k, and my machine never feels slow to me. My OCR reader s slow, but that generally runs in the background.

One benefit the of the 5k imac is that it's great for working with historical documents-- provided the scans are high enough resolution.

(imac 2014, 5k, i5, m290x, 24 GB memory)