Resolve on 2017 iMac: Opinion on i5 vs i7

I'm considering upgrading my computer to one of the new 2017 iMacs with Radeon Pro 580 (8GB) video, and was wondering how much of a consideration I should put between the i5 or i7 CPU.

Apple Canada currently has a 2017 i5 in the refurbished section, which would save a bit of money, but if I needed to opt for the i7, I would have to buy new.

Does anyone have a recommendation either way?

What kind of projects do you work on, and what sort of media?

My projects vary widely. For the most part, my long-form projects (> 1/2 hour) would mostly be 1080p ProRes. I'm just getting into 4K RAW (from URSA Mini 4K) which would mostly be short presentation projects (e.g. few seconds to under 1/2 hour). Media would be external SSD's via USB-3.

The biggest concern is not painting myself into a corner in one or two years. I'll never be able to afford the upcoming iMac Pro nor newer Mac Pros, and the current Mac Pros sound like a dead-end, especially with everyone reporting problems using Resolve.

Yep, it's bit of a problem with recent Apple pricing. iMacs are nice, but quite expensive and in the same time still lack of pure power sometimes.
You may need to go to PC, where it's easier to do things on budget.

While I haven't completely ruled out a Windows PC, I'm reluctant to go that route because it's a minefield of configuration options, and I don't want to risk wasting time and money on a lot of trial-and-error. (Been down that road many times before.)

One reason I'm considering the 2017 iMac versus any prior Mac is that Apple will be officially supporting external GPU's via Thunderbolt 3, giving them a bit of an upgrade path iMacs haven't really had before. (At least that's the hope; reality may be quite different.)

My main objective with this post is just to determine if there is enough of a benefit of going for an i7 CPU over the i5.

Earl, it's pretty simple to get a sweet windoze machine here in Vancouver, there's a few folks who know how to build them, Paul @ NewType Copmputers on Pacfic bvld can build you a machine that works well for Resolve, he builds alot of machines for the VFX biz localy

IGS systems in TO have some z840's on offer with 3yr HP gold support, they and also build them into Resolve spec, abut that's geting up into TrashCan range, vastly more compentent machine tho

While I haven't completely ruled out a Windows PC, I'm reluctant to go that route...

One of the other reasons is ProRes. A lot of my current work involves ProRes, so that would be a hassle on Windows.

Earl, it's pretty simple to get a sweet windoze machine...Paul @ NewType Computers on Pacfic bvld can build you a machine that works well for Resolve

Thanks, that's a good reference to have.

Hmmm, if you wan to later extend your GPU over TB3 then you rather want i7. 4 cores is not that much for Resolve anyway- make sure they are high clock.
Just remember that TB3 data bus is over PCI-E x4 connection, so GPU will be in some case bit hit by this.

I was wondering myself, but I will decide for the i5. From all my research I found that i7 will run extremely hot in an iMac, which will increase noise and decrease life span (think future proof). The 580 Radeon Pro with it's very welcome speed boost will already add quite a bit of heat in those tight quarters. Even the older iMacs with i7 run their processor much hotter than properly cooled PCs do.

If I could afford it (I can't) I'd be very reluctant to go for an iMac Pro for the same reason. I doubt that Apple will handle the enormous amounts of heat very well in that stylish case. I'd wait till others get burnt (maybe literally). Apple made that mistake once with the MacPro, violating the most important rule in design:

Form follows function!

P.S.
I used to be a die-hard Apple fan since I switched from windows around 2000. But these days I'm seriously considering a PC again. Maybe after Steve Jobs died, Apple was taken over by the usual capitalist "grab what you can and don't care for your buyers needs". Of course they were a capitalist enterprise before, but at least one with a vision. The iMac I'm buying now might be the last one for me, if they don't deliver.

Please, no PC vs Mac discussion, but I'm looking forward to your voices about i5 vs i7 specifically for Resolve.

Different look. If they are both the same clock then yes you can use i5. But if this is eg 2.5GHz i5 v 3.5GHz i7 then this is huge processing power difference.
If you are already concern about heat then this is bad sign.

Well, with the 580 GPU it's 3.8GHz i5 vs 4.2GHz i7 (so, about 11 % more) and I doubt it will keep Turbo Boost on for extended periods.

11% on clock+ probably another 10% on i5 v i7. At the end it's already quite a big difference in machine where you can't change CPU after year or 2.

In my opinion, subject to your budget, you want to be on the best CPU that the iMac offers. When you generate optimized media, all those CPU threads will cobble up whatever you throw at it and I don't think the GPU is even involved. I'm late to the party, but since I favour shooting raw, optimizing the media to ProRes 444 is part of my workflow now.


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Yeah, maybe 20%, but that machine is standing right in front of me if it's getting noisy.

I never even thought of noise with our upgraded "cheesegraters", since we put them behind a wall, but with an iMac I do.

Plus, if it's really running as hot as many sources say, it might not survive for long after the 3 years of Apple care anyway.

If this is the case then I would simply not buy iMac. It looks like it's just a shiny machine just for we browsing and maybe bit of Photoshop and plain editing.
I also fear that iMac Pro with these up to 18 cores Xeons will end up having same issues as Mac PRO.
You either have that power available to our or not. I don't want it just in theory

Amen, Andrew. Don't these designers ever actually use the machines (or hire their target 'professional' to use them the way they will) on complex and long projects?

That's a rhetorical question since the answer is too obvious.


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But they look so cool in Hollywood movies…

Why don't they make Cheesegrater boxes any more? Whatever you cram into them, I never had thermal issues.

There's a newer Mac Pro coming as early as December 2018 or early 2019. Although the Trashcan had its appeal, I'm not sure Apple will stick with that basic form in the next generation. Kudos for risking something different, but I think it fell short of its promise. The next version may be much better as they learn more from mistakes than from successes.


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So, my iMac with the Radeon Pro 580 and i5 CPU is here, and I think it was the right decision.

If I throw something at it like H.264 encoding in UHD, it get's hot, but not too loud. The CPUs run over 90% load and get to over 90 degrees, without showing me a red bar in TG Pro, with the GPU considerably cooler than the CPU and the fan noise still acceptable. BTW, no difference between the free version and Studio here.

If it runs into circles, like trying to encode VP9 in DR (which is reliably crashing the software), all CPU cores run at the limit and get close to 100%. The fans blow full speed and it becomes too noisy to sit in front.

Given the extra power to be handled from an i7, I doubt I'd like to sit there while encoding or rendering.
Yes, I need to transcode formats like UHD with more than 8 bit in H.264 or any H.265.

But all 8 bit H.264 runs smoothly to my hearts delight without transcoding, just like in FCP-X.