iMac 21 4K

JokerPower

macrumors regular
Original poster
Aug 12, 2017
114
119
Hello

What upgrades should I get for iMac 21 4K?

There is several options:
- 3.0 GHz quad-core i5 (7th generation) versus 3.4 GHz quad-core i5 (7th generation) versus 3.6 GHz quad-core i7 (7th generation)
- 8 GB RAM versus 16 GB RAM
- 1 TB Fusion Drive versus 512 GB SSD

I'm thinking of getting cheaper 3.0 GHz quad-core i5 and more RAM/SSD.

Here is 4 builds:

V1

3.4GHz quad-core 7th-generation Intel Core i5 processor, Turbo Boost up to 3.8GHz
16GB 2400MHz DDR4
512GB SSD
Radeon Pro 560 with 4GB video memory
Magic Mouse 2 + Magic Trackpad 2
Magic Keyboard - US

2348 euro


V2

3.0GHz quad-core 7th-generation Intel Core i5 processor, Turbo Boost up to 3.5GHz
16GB 2400MHz DDR4
512GB SSD
Radeon Pro 555 with 2GB video memory
Magic Mouse 2 + Magic Trackpad 2
Magic Keyboard - US

2273 euro


V3
3.4GHz quad-core 7th-generation Intel Core i5 processor, Turbo Boost up to 3.8GHz
8GB 2400MHz DDR4
512GB SSD
Radeon Pro 560 with 4GB video memory
Magic Mouse 2 + Magic Trackpad 2
Magic Keyboard - US

2122 euro


V4

3.4GHz quad-core 7th-generation Intel Core i5 processor, Turbo Boost up to 3.8GHz
16GB 2400MHz DDR4
1TB Fusion Drive
Radeon Pro 560 with 4GB video memory
Magic Mouse 2 + Magic Trackpad 2
Magic Keyboard - US

2009 euro


V5

3.0GHz quad-core 7th-generation Intel Core i5 processor, Turbo Boost up to 3.5GHz
16GB 2400MHz DDR4
1TB Fusion Drive
Radeon Pro 555 with 2GB video memory
Magic Mouse 2 + Magic Trackpad 2
Magic Keyboard - US

1934 euro


What do you think?

For general usage, no professional tasks (only some photo editing).

Thanks a lot
 
Last edited:

vojislavsh

macrumors member
Aug 5, 2018
51
16
Podgorica, Montenegro
I would go with radeon 560 (4gb vram) , better for future proofing. The i5 with 3.4ghz is enough . I have 8gb ram , but in my imac 27 i can add ram, so far didn’t experience any problems with performance. Also i must say a have a fusion drive but i plan to add external ssd as boot drive in future. I come from a HDD comp so for me even fusion drive is super fast.
So V1 config , even with 256gb ssd is my favourite.
After V1 , V4 is the best.
 
  • Like
Reactions: JokerPower

bbnck

macrumors 6502a
Mar 19, 2009
567
311
The 3.0 GHz (i5-7400) quad-core CPU will be more than adequate for your needs. Combine that with 16 GB RAM and 512 GB SSD and you've got yourself a very capable machine.

Here's the difference in synthetic benchmarks between the 3.0 GHz (i5-7400) and 3.4 GHz (i5-7500):

upload_2018-9-23_12-57-31.png

upload_2018-9-23_12-57-44.png

I'm a software engineer so I often have a lot of pro apps in use when work gets busy, but I can certainly get by on a 13-inch MacBook Pro with a dual-core 2.3 GHz (i5-7360U) processor, which is the machine I have at work. From synthetic benchmarks, it's about 33% slower in multi-core tasks than the 3.4 GHz (i5-7500) iMac. Point being, the 3.0 GHz Intel Core i5 is a fine choice.
 
Last edited:
  • Like
Reactions: JokerPower

JokerPower

macrumors regular
Original poster
Aug 12, 2017
114
119
The only drawback with 3.0 CPU is that there less powerful GPU

What about 1 TB Fusion Drive vs 512 GB SSD?
 

bbnck

macrumors 6502a
Mar 19, 2009
567
311
The only drawback with 3.0 CPU is that there less powerful GPU
Yes you're right the only drawback here is the less powerful GPU but the 560 is still very capable and if you compare it to the 570, you have to bear in mind it's also having to power a 5K display (the 27-inch iMac has over 5 million more pixels). This synthetic benchmark comparison might help though: http://gpuboss.com/gpus/Radeon-Pro-570-vs-Radeon-Pro-560#performance

What about 1 TB Fusion Drive vs 512 GB SSD?
Well, I don't notice a massive difference with the 1 TB Fusion Drive in my 2017 iMac compared to my 2017 MacBook Pro when it comes to app launch times. You might get claims from others that the Fusion Drive is substantially slower than an SSD but not in my observation. I have witnessed apps bounce on the Dock for longer on my MacBook Pro than my iMac. Usually the MacBook Pro is a little quicker to launch apps but not always. macOS does a good job of balancing what needs to be on the SSD portion of a Fusion Drive system.

If you don't want to spend the extra money, you will be happy with the Fusion Drive if you don't do any work that relies on high I/O throughput, but you might get an extra year or two out of your machine with an SSD before you feel you need to upgrade to a new machine. Mechanical drives tend to get slower as they age (but we're talking well over five years – I was using a colleagues' 2013 iMac last month and the 7200-rpm hard drive still seemed as quick as I'd expect from it). I'm not suggesting Fusion Drives or mechanical drives don't last as long – they do – but SSDs generally provide the same performance until the very end. Unlike mechanical drives, SSDs fail suddenly when they reach the end of their lifespan. This is the nature of solid state storage. However it's not uncommon to see mechanical drives and SSDs still functional after a decade. Whether the computer they are in is still useful is another matter.

Another option is to keep the 1 TB Fusion Drive or upgrade to a smaller 256 GB SSD and buy an external Thunderbolt 3 SSD to serve as the boot drive (you can use CarbonCopyCloner to clone the internal drive onto the external SSD). Or use a smaller internal SSD as the boot drive and use the external Thunderbolt 3 SSD as external storage for your photography work and any other large files. That way, you can unplug the external drive when you don't need to use it. But these options obviously present an extra expense here that might not be acceptable to you. Your call.

Knowing that a Fusion Drive offers good I/O performance and an SSD offers maximum I/O performance, it all comes down to cost and what your priorities are. Some pro users will argue their work demands an SSD. Other pro users will argue that the cost is not justified when a Fusion Drive provides a good balance for a lot of workflows.

Based on the cost of these upgrades in Germany, an upgrade to a 256 GB SSD costs 120,00 € and a 512 GB SSD costs 360,00 €. Make a judgement call whether or not you want to spend extra for the SSD upgrade.
 
Last edited:
  • Like
Reactions: JokerPower

JokerPower

macrumors regular
Original poster
Aug 12, 2017
114
119
Yes you're right the only drawback here is the less powerful GPU but the 560 is still very capable and if you compare it to the 570, you have to bear in mind it's also having to power a 5K display (the 27-inch iMac has over 5 million more pixels). This synthetic benchmark comparison might help though: http://gpuboss.com/gpus/Radeon-Pro-570-vs-Radeon-Pro-560#performance



Well, I don't notice a massive difference with the 1 TB Fusion Drive in my 2017 iMac compared to my 2017 MacBook Pro when it comes to app launch times. You might get claims from others that the Fusion Drive is substantially slower than an SSD, but not in my observation. I have witnessed apps bounce longer on the Dock on my MacBook Pro than my iMac.

If you don't want to spend the extra money, you will be happy with the Fusion Drive if you don't do any work that relies on high I/O throughput, but you might get an extra year or two out of your machine with an SSD before you feel you need to upgrade to a new machine. Mechanical drives tend to get slower as they age (but we're talking well over five years – I was using a colleagues' 2013 iMac last month and the 7200-rpm hard drive still seemed as quick as I'd expect from it). I'm not suggesting Fusion Drives or mechanical drives don't last as long – they do – but SSDs generally provide the same performance until the very end. Unlike mechanical drives, SSDs fail suddenly when they reach the end of their lifespan. This is the nature of solid state storage. However it's not uncommon to see mechanical drives and SSDs still functional after a decade. Whether the computer they are in is still useful is another matter entirely.

Another option is to keep the 1 TB Fusion Drive or upgrade to a smaller 256 GB SSD and buy an external Thunderbolt 3 SSD to act as the boot drive (you can use CarbonCopyCloner to do this). Or even easier, keep the Fusion Drive or the smaller internal SSD as the boot drive and use the external Thunderbolt 3 SSD as external storage for your photography work and any other large files. That way, you can unplug the external drive when you don't need to use it.

Knowing that a Fusion Drive offers good I/O performance and an SSD offers maximum I/O performance, it all comes down to cost and what your priorities are. Some pro users will argue their work demands an SSD. Other pro users will argue that the cost is not justified when a Fusion Drive provides a good balance for a lot of workflows.

Based on the cost of these upgrades in Germany, an upgrade to a 256 GB SSD costs 120,00 € and a 512 GB SSD costs 360,00 €. Make a judgement call whether or not you want to spend extra for the SSD upgrade.
Thanks for detailed explanation, appreciate it

Regarding the CPU, 570 is available only for 27 inch Macs. So there is 2 options for 21 inch:
- 555 2GB available with 3.0 GHz i5
- 560 4GB available with 3.4 GHz i5

In general, I'm not very bound to GPU performance, but as you know, this can't be upgraded in the future.. so maybe there is a point not to go with 3.0 GHz CPU

I'm using MBP 13 inch 2017, non-TB, and it runs ok with 8GB RAM, but I'm thinking that this can minimal for an 4K iMac.. what do you think?

So you're suggesting to go with Fusion Drive and invest in more RAM, better CPU&Video?
 

bbnck

macrumors 6502a
Mar 19, 2009
567
311
Thanks for detailed explanation, appreciate it

Regarding the CPU, 570 is available only for 27 inch Macs. So there is 2 options for 21 inch:
- 555 2GB available with 3.0 GHz i5
- 560 4GB available with 3.4 GHz i5

In general, I'm not very bound to GPU performance, but as you know, this can't be upgraded in the future.. so maybe there is a point not to go with 3.0 GHz CPU

I'm using MBP 13 inch 2017, non-TB, and it runs ok with 8GB RAM, but I'm thinking that this can minimal for an 4K iMac.. what do you think?

So you're suggesting to go with Fusion Drive and invest in more RAM, better CPU&Video?
Well, first definitely avoid the 5400-rpm hard drive in the 3.0 GHz iMac. Should have pointed that out sooner. That is a slow piece of crap compared to a Fusion Drive or SSD and is unsuitable for anyone that does pro work, even light photography.

You've seen the benchmarks between the 3.0 GHz and 3.4 GHz processors, so it's your call. I can't really say it's a good or bad idea because it's a question of longetivity and I can't really predict how you might use your machine down the line.

When you're really busy on your MacBook Pro, check Activity Monitor and from the Memory tab, see what the memory pressure is like. I would also be fine with 8 GB RAM if I didn't need to use VMs which can take 1 GB - 4 GB of RAM alone, which is why I need 16 GB RAM.

If it was a 27-inch iMac you were going for, I would suggest staying at 8 GB because you would be able to upgrade it yourself later on down the road by simply buying the correct DIMM modules from a retailer like Crucial. However the 21.5-inch 2017 iMac does not have a RAM access door on the back of the machine despite the memory being socketed, so you would need to take it into an Apple Authorised Service Provider in order to get more memory installed, which will be even more expensive than ordering the machine with an extra 8 GB RAM.

Again this is one of those questions of longetivity and it's a call you need to make based on your current needs and what you see your usage likely to be down the road. It's reasonable to decide to order something a little more powerful than you might need (as you mention, an iMac with 3.4 GHz i5 instead of a 3.0 GHz i5). It's certainly not a ridiculous idea and many people make this call when going over their buying decision.

I'm not necessarily recommending a Fusion Drive over an SSD (obviously there's a cost element), but what I am saying is that a Fusion Drive will serve you well if you really don't want to spend extra money on an SSD. Fusion Drives offer a good capacity to performance ratio. If you want maximum I/O performance and want all of your apps and photos to open as quickly as possible no matter how much storage space you're using, then you need to spend more and upgrade to an SSD. However the Fusion Drive system keeps your most frequently used apps and files on the SSD and it does that well. Again I have two machines to offer a fair comparison between an SSD and a Fusion Drive.

I know it might be easier if I just told you what to get, but you need to make that decision for yourself based on what you feel is best with all the information you have to hand.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.