Deciding which iMac to get

For long-term use, I would get 16 GB of RAM. Eight is fine for now, but in a few years, you'll be wishing you had 16.

Next on the list of upgrades, if you can afford it, would be a Fusion drive.

Last, but certainly not least, would be the graphics card.

 

As someone who is tired of waiting for the mini refresh I'm about to order a 21" imac. The base 2.7GHz I5 4570R has Iris Pro graphics 5200 which is only about 5% slower than the GeForce 750m. In some situation it'll even perform better. It's also a quad-core so that's nice. Upgrade the RAM for sure and if you can go for the fusion drive or 256Gb SSD (if you already have an external drive for storage) then go for it.

 

I have the Late 2013 iMac 21.5" high end with the Nvidia Geforce GT 750m 1Gb GDDR5. I wouldn't say that you should upgrade the RAM just because it can't be done later. When I thought about it, I realised I wouldn't have upgraded it down the line anyway. When running 23 Applications at once (like iMovie, Pages, Numbers, Keynote, iTunes, iPhoto, Maps with 3D, App Store, Safari with a few tabs, Chrome with a few tabs... that sort of thing), I was only using 5.5Gb of RAM (1.5Gb of that was also App Cache). So I would still have 2.5Gb of RAM before it clears the App Cache, where I would then use another 1.5Gb before it starts to compress RAM, where I would then have another 4Gb before it starts to violently swap to hard disk.

So in the end, while running 23 (mid - heavy) Applications, I was only pushing the RAM to 40% of what it could handle. And the RAM pressure was still green throughout as well as very low. Seeing as I only run 1-3 Applications at once, 8Gb will last me at least 5 years. If you only a few applications at once (like when you render a video, do you just surf the web while you wait, or do you play a game/edit in photoshop?), then just save yourself £160 and stick with 8Gb. The processor and GPU will be too slow anyway by the time you really need 16Gb.

As for the fusion drive, I'd say stick with the HDD, or go full SSD. The places the FD will help are boot up and launching Applications for the first time. You only boot up once every 3 months, and Applications load instantly on a HDD with App Caching in Mavericks. And if one portion of the drive fails, the whole thing fails. Pro's of an SSD is much faster import/exporting, reliability, and quietness.

 

I'd say you would be best with either the Entry level 21.5" iMac with 256Gb SSD, or the high end 21.5" iMac with SSD and GT 750m. The 200Mhz difference between the low end and the high end is not all that big, but once it turboboosts, the difference is 400Mhz between them which would have some sort of a noticeable affect. From what I have found, the processor in the 2.9Ghz iMac is roughly 11+% faster at average CPU tasks when compared to the 2.7Ghz. It also contains 50% more L3 cache (6Mb in the 2.9Ghz, 4Mb in the 2.7Ghz) which would also improve performance.

Along with the processor upgrade, the GT 750m (in my opinion and personal experience) is a great card. I ran the Dirt 2 demo and it gets around double the performance as the Iris Pro (I got around 72fps when maxed out). Iris Pro is really said to be "good enough to get the job done", but when it comes to 3D rendering, the GT 750m destroys the Iris Pro. The 750m also has CUDA support.

One thing to also remember, you are indirectly getting 1Gb of more RAM by getting the GT 750m. This is because it comes with 1Gb of GDDR5 VRAM. The Iris Pro comes with 128Mb of DRAM, but will also being using system RAM as VRAM. So when pushing your system graphically, the Iris Pro will be using 1Gb of your system RAM, where as the 750m has it's own dedicated memory. I should also point out that the Iris Pro can use as little as something like 27Mb of system RAM as VRAM.

From my experience, I have been able to export (from iMovie) a 1hr 45m HD 1080p video (consisting of an average of 3 layers of video at all times, 2 layers of audio most of the time, video stabilisation for a few parts, lots of audio enhancements, and simple edits like tone edits...) and it rendered and exported it in around 20-25 minutes! Extremely fast. And that was with a HDD (the file size of the exported video was 10.5Gb!), the SSD really would help with the export times.

So really, the CPU upgrade in the high end model (2.9 vs 2.7) will have a noticeable affect when doing CPU intensive (so if you want to export/render/encode video... then it will help get things done quicker), and the GT 750m will be great if you wish to do any sort of rendering (both 2D and 3D, with the later having a massive affect when compared to the lower performing Iris Pro in 3D rendering).

I'd say your best bet (especially if you wish to keep it for the 5+ kind of range), is the 2.9Ghz iMac 21.5" with the GT 750m and the 256 SSD.

Hope this helped

 

The 2.7 I5 is quad-core with Iris Pro. The upgrade to the 2.9 I5 and 750m is about a 15% increase in performance in graphics heavy applications.

IMO, I'd rather have the RAM and Iris Pro. Or if you can wait for the iMac refresh this fall, it may include nVidia's new 800 series mobile GPUs which actually have some balls. If you're looking to play games, the 750m will leave you wanting more...

 

Not a problem. When you are editing a video, the 2.9Ghz processor with the GT 750m will help you get work done more smoothly and will be more responsive than the entry level iMac. When it comes to rendering and exporting the video, the rendering will be noticeably faster (the longer the video, the more noticeable it would be) with a higher end CPU (as well as the much larger difference between the 2.7 and the 2.9 when turboboosting) and a dedicated GPU (as the GPU is used for certain jobs, and the 1Gb of GDDR5 VRAM will help a lot when compared to the Iris Pro using DDR3 RAM as VRAM (coupled along with 128Mb of DRAM)). Then when it comes to the exporting part, the SSD will be able to write the video to disk at a rate of 650Mbps. A Fusion Drive on the other hand would right at around the 300-350Mbps mark. So exporting with the SSD will be around 2X the speed.

One other thing to note, Apple appear to be moving to pushing more CPU tasks and reconstructing them to be computed on the GPU. This has great affects, as tasks that have been reconstructed to be done on the GPU yield 5 to 10 X speed increases. This is the reason the Mac Pro comes standard with dual GPU's. And because the data transfer speeds between the 750m and it's 1Gb of GDDR5 VRAM is much faster then the Iris Pro getting data from DDR3 RAM, this would be hugely helpful in the future. There are already a few programs out there on Mac that use such techniques, but it appears the future of computing is have very power GPU's, not CPU's. In the future, powerful GPU's will make up for weaker CPU's, so buying the most powerful GPU now means in the future (when both the 2.7 and 2.9GHz) processors are seen as slow, the 750m would be what really makes the machine pull away from the 2.7Ghz and could get you some extra time before an upgrade.

When it comes to RAM, there has been a lot real-world-tests carried out that shown the speed increase (in games, rendering and exporting a video, importing/exporting files in Photoshop...) between 4Gb of RAM and 8Gb of RAM was very big. But when it came to trying the same tests on the 8Gb of RAM vs 16Gb, there was next to no difference. 16Gb of RAM will only improve system performance over heavy load (and from my one of my earlier comments, the "heavy load" would have to be very heavy seeing as I can run 23 heavy applications at the same time and only push the 8Gb of system RAM 40%). Unless you plan to render a video in OSX, play a game, and run a Virtual Machine or two all at the same time (like running Windows 7 and 8 while running OSX at the same time), the 8Gb of RAM will defiantly be enough to last you through the lifetime of the computer.

I was really in the same position as you, as I too do a lot of video editing (nothing too professional though) for college. I have the 2.9Ghz 21.5" iMac with 8Gb of RAM, Nvidia GeForce GT 750m, and a 1Tb HDD and am very pleased with my decision. If you are wondering why I went for the Hard Drive, I needed 1Tb of space, I couldn't afford the 1Tb SSD, and the 1Tb FD was not worth £160 for the small benefits it brings.

I would also recommend waiting to the fall for a new model (which will most likely sport a slight spec increase in the CPU [3.0Ghz instead of 2.9Ghz, from Intel's new Haswell updates], and a Nvidia 800 series GPU [most likely the 850m]).
So to recap, the best option I recommend for you is the 3.0Ghz (turboboost to 3.7Ghz) i5, 8Gb of RAM, Nvidia GeForce 800 series GPU (or the dedicated GPU), 256Gb SSD.

If you have any other questions, don't hesitate to ask

 

You and MartinApplyGuy have also helped me with this frustrating decision. Sometimes I really hate computers. I digress... I too will be waiting until the fall because by that time the 850m should replace the 750m. I was surprised to find last night that the 800m series is already available on new machines. And while the 750m is basically a more thermally efficient 650m, the 850m is 60% more powerful than it's predecessor. The other interesting thing I learned last night is there are direct replacements coming from Intel for all chips EXCEPT the base I5 with Iris Pro. The are to be released next month I believe meaning a June/July iMac update is likely. You may not have to wait until fall!

MartinApplyGuy made some really good points regarding video editing and rendering, which is my main purpose for a new machine. Thanks Guy!

 

Hi there, chelch. Happy to help

I defiantly agree with the waiting, 3 months waiting gives you a 12 month newer machine. For my conclusion in my last comment, I think I should rephrase and say: the high end 21.5" (with dedicated graphics, most likely the GT 850m) and the 256 SSD upgrade for the OP.