iMac for Photoshop - CPU vs GPU vs RAM?

[pavinder]

I'm planning to upgrade my late 2013 iMac (3.4 GHz i5, 16GB RAM) to a new iMac.

Other than web browsing/playing music/movies, my main use is for Photoshop work. I work on large multilayered files up to 3GB or occasionally more. All files are stored on external 4TB hard drives.

I currently boot from an external SSD (512GB SanDisk Extreme Pro) as the internal Fusion drive died.

I'm basically trying to understand the relative importance of CPU vs GPU vs RAM for Photoshop work.

1. Would the 3.8GHz processor be noticeably faster or would the base model 3.4 GHz be fine?
2. Would simply adding more RAM (to 16GB or 32GB) to the base model make a bigger difference for Photoshop than spending my money on the faster processor or better GPU?

Thanks in advance for advice.

 

[Lunder89]

If you are thinking about spending more money on the processor, I would spend it going to the i7 processor. The 400 MHz gained per core is not going to make that much of a difference. Going for the i7 on the model with the Radeon 575, costs the same as the i5 top model.

If you have more than one file open at 3GB size, I would go for the 32 GB ram, but you might wanna buy that somewhere else than Apple, to keep the costs down. With the 27" you still have access to replace the memory on your own.

I don't know how much Photoshop actually uses the graphics card nowadays, but I don't think you will get much out of
prioritizing the GPU.

 

[pavinder]

I wondered if the i7 would make a big difference. It seems there is a lot of conflicting information about the relative value of CPU vs GPU vs RAM (beyond 16GB).

The only consensus seems to be that an SSD rather than Fusion drive is recommended.

 

[ThatSandWyrm]

I'm planning to upgrade my late 2013 iMac (3.4 GHz i5, 16GB RAM) to a new iMac.

Other than web browsing/playing music/movies, my main use is for Photoshop work. I work on large multilayered files up to 3GB or occasionally more. All files are stored on external 4TB hard drives.

I currently boot from an external SSD (512GB SanDisk Extreme Pro) as the internal Fusion drive died.

I'm basically trying to understand the relative importance of CPU vs GPU vs RAM for Photoshop work.

1. Would the 3.8GHz processor be noticeably faster or would the base model 3.4 GHz be fine?
2. Would simply adding more RAM (to 16GB or 32GB) to the base model make a bigger difference for Photoshop than spending my money on the faster processor or better GPU?

Thanks in advance for advice.

1) No, go for the i7.
2) Only if you're regularly swapping to disk now. In the lower left-hand corner of Photoshop, chose the "Scratch Sizes" option. If the first number is always less than the second, you don't need more RAM. Also remember that Photoshop's RAM is allocated manually by the user in performance preferences, not by MacOS. So if you didn't know that, you might be using less RAM than you actually have available.

I'm a heavy Photoshop user, and I never needed more than half of the 24GB of RAM in my last iMac.

Photoshop barely uses a GPU, if at all. Pretty much any one will do.

 

[Lunder89]

The i7 is faster yes, but the speed increase can be limited, based on the app you use.
Now I am simplifying my answer here.
The benefit of the i7, is the way it handles cores and logical cores.
Logical cores is not physical cores, it is simply a "trick" to make the computer think that additional cores are available. That way a process can have more threads (Or motorways into the processor, giving it that extra performance)

An i5 processor consists of 4 CPU cores, and no logical cores.
An i7 processer consists of 4 CPU cores and 4 logical cores, so it looks to the system like it has 8 cores total.
If the software you use can take advantage of that, you can get extra performance out of it. If not, it doesn't really mean anything.

Now let me make a simpel example of this. I used to be a DJ, and needed my audio files in a very specific format, to not upset my DJ mixer.
The conversion software I used could take advantage of the extra logical cores when present.
On my i5 Mac, it would convert 4 tracks at a time (2015, 27" 5K iMac)
On my i7 Mac, it would convert 8 tracks at a time (2014, 15" MacBook Pro)
I didn't do a benchmark on which did the same task the fastest.

I don't use Photoshop all that much, and when I do, the files are never in that size, and the edits very simple.
I do however do video editing. Recently in 4K.
My iMac's i5 compared to my 2014 MacBook Pro's i7. I know its the 3xxx generation in the MacBook Pro, and the 6xxx generation in the iMac, but still, the iMac is a little faster and a little smoother, in the same software (Premiere Pro), and yeah I know the comparison is far from ideal.

Going for a stronger i5, will maybe make 5% difference and going for the i7 might make 10-15% difference, I don't know if it is worth it, or if you even need it.

Try to keep an eye on on activity monitor when using Photoshop, and see what it says. You can change the update rate to every second, and the Dock icon to CPU-meter, that way, you can keep an eye on how high it goes with your current setup.

 

[pavinder]

Thank you for the explanations of exactly how things might help. It makes things a lot clearer.

Much appreciated for the advice. I'll start monitoring activity more closely and check memory allocations, and plan my new system accordingly.

 

[EugW]

Personally I’d recommend waiting for the 2018 models, likely coming in a few months. They will be going 6-core.

For Photoshop it won’t help as much as with other apps but for some actions it will help.

Get something like an i5-8600K or an i5-8600. The i5-8600K is already a reality, but the i5-8600 is speculated by many to appear in a few months. Or else something like a possible i5-8500 would also be a good option.

 

[OBirder]

I think the sequence of importance for you should be:

1. SSD - already mentioned - will increase the whole experience - starting, loading etc. - Keep the current project on SSD - Non current projects can stay on external HDD
2. RAM - While I see comments that indicate that you enough for Photoshop, the reality is that at times you have several program open e.g. Lightroom, Photoshop, Illustrator, InDesign ... The extra RAM will help
3. CPU - Similar to the RAM, while only for Photoshop you may not need the i7, but with several programs running in parallel it will help
4. GPU - Probably least worry. It seems that Adobe products seem not take advantage. I actually turned off in Lightroom to use the GPU and it seems to be faster (iMP with Vega 64).

Good luck.

 

[abetancort]

It seems that we are all guessing when we refer to current iMac and adobe photographic software (Photoshop and Lightroom) for photographers that shoot large raw files:

- Hard drive: There is consensus to go with SSD and the more you can afford the better.

- Memory: There is consensus that going above 32 Gb is a waste of money.

- Processor: i5 3.8 GHz vs i7 4.2 GHz processor type, there is no clear answer which one gives more value. Does anyone knows how well and in which processes do the aforementioned apps use multithreading efficiently? An what is the roadmap of adobe with regards to this within a 1 to 4 years range.

- Graphic card: AMD Radeon Pro Mod. 575 4Gb ram. vs 580 8Gb ram. There’s no consensus or clear explanation which one will give the most value.

 

[mpe]

- Memory: There is consensus that going above 32 Gb is a waste of money..

It all depends on how big the project is (how many pixels, bit depth and layers used). When the decoded project exceeds the RAM the performance of Photoshop quickly deteriorates. If a work involves dealing with stitched panoramas or opening multiple huge pictures as layers it is not impossible make a 32GB system unworkable. But there is a chance the OP would know if he was doing that.

- Processor: i5 3.8 GHz vs i7 4.2 GHz processor type, there is no clear answer which one gives more value. Does anyone knows how well and in which processes do the aforementioned apps use multithreading efficiently? An what is the roadmap of adobe with regards to this within a 1 to 4 years range.

The i5 vs i7. It is not only about hyper threading. i7 models often have bigger cache and more aggressive frequency multipliers than i5 models. So they are in generally faster at any workload. But we are talking about 20% difference or so not more. However, whatever the Adobe roadmap is it won't make any difference. The i7 will always be about 20% faster, today or in 4 years time.

My suggestion:

iMac 2017 with 4.2 GHz i7, 8GB RAM, 512 of internal SSD storage, Radeon Pro 575

Then buy a 3rd party memory upgrade to 32GB and a decent external USB-C hard-drive for finished projects.

 

[abetancort]

I finally went for an:

• iMac 27-5K i7 4,2, 8 GB Ram, 1TB SSD, RadeonPro580 8GB
• Upgraded the ram to 40 GB by adding two Crucial CT16G4S24AM - (16 GB, DDR4, 2400 MT/s, PC4-19200, DR x8 Unbuffered, SODIMM, 260-Pin).

Now I am looking:

1. Add another 1TB or 2TB of external storage over USB 3.1 to save all photos and projects waiting to be finish and move to the internal drive only the ones I’m working in that session (I don’t want to use more than 50% of the internal SSD as its performance will degrade quickly when going over that usage).
2. Add a 4TB hard drive USB 3.1 for near backups, because I all already have 10TB NAS for archival purposes on the Lan.