Memory: 24GB 1600MHz or 16GB 1867MHz?

[Edgecliff]

Short story
What memory is preferable: 24GB at 1600MHz or 16GB at 1867MHz?

Long story
We've got two iMacs (5K, Late 2015) with 8GB (2x4) 1867MHz CAS13 default memory.
I've bought an additional 32GB (4x8) 1867MHz CAS11 memory.

Turns out when I let both iMacs run on 24GB (2x4 plus 2x8) it bumps down the speed to 1600MHz due to CAS latency difference.

An option would be configuring one iMac as 16GB (4x4) and the other as 32GB (4x8). This way they run both on 1867MHz since there's no difference in CAS latency.

Runs an iMac better on 16GB 1867MHz or should I stay with 24GB 1600MHz for both models?

 

[Floris]

If I were to buy todays iMac, I would keep the 8gb in there, and just add 2x 8gb on top of it.
ram is still faster than ssd drives, and adobe software loves ram.

 

[jerwin]

what applications are you running on each?

I have 24 gb.

It's not all that useful. Usually when I need that much memory, it's not the bottleneck.

 

[Floris]

Guess I have mine better configured then.

 

[Edgecliff]

what applications are you running on each?

Mostly Creative Cloud applications; heavy image processing and video editing. 16GB will be enough voor 3/4 of the time, though.

That's why I'd like to know if 16GB at 1867MHz will give a significantly better overall performance than 24GB at 1600MHz. Anyone?

 

[jerwin]

In my opinion, you have the perfect setup for benchmarking--two otherwise identical machines running the same software. You can measure whether 24 GB of slow ram is faster than 16 GB of fast ram-- for the sort of workloads that you do.

...and if you want something a little more systematic

https://macperformanceguide.com/OptimizingPhotoshopCS6-Benchmarks.html
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Guess I have mine better configured then.

It depends on what software you use. When Safari tries to allocate upwards of 15 GB, it usually means that something is seriously wrong with one of the webpages. When Photoshop allocates that much memory, it's normal.
Some programs will allocate no more than 3.01 GB-- because the programmer has built that limitation into to the program-- even when using more RAM would allow the use of deeper search trees, and faster execution times.

 

[Floris]

In my opinion, you have the perfect setup for benchmarking--two otherwise identical machines running the same software. You can measure whether 24 GB of slow ram is faster than 16 GB of fast ram-- for the sort of workloads that you do.

...and if you want something a little more systematic

https://macperformanceguide.com/OptimizingPhotoshopCS6-Benchmarks.html
[doublepost=1477697436][/doublepost]
It depends on what software you use. When Safari tries to allocate upwards of 15 GB, it usually means that something is seriously wrong with one of the webpages. When Photoshop allocates that much memory, it's normal.
Some programs will allocate no more than 3.01 GB-- because the programmer has built that limitation into to the program-- even when using more RAM would allow the use of deeper search trees, and faster execution times.

That only happens when you browse theVerge ;p