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Benefits of a i7 iMac over an i5 iMac?

Zach Schible

Zach Schible

macrumors member
Original poster
Jun 19, 2009
56
0
Indiana
So I am very close to getting a new iMac and I am torn between the i5 and i7. While the i5 would suite me fine now I am wondering if I would be missing anything in the future that the i7 offers.

Work being done on this Mac will be Lightroom, Photoshop, Web development apps, and basic movie editing programs. For the work I do I need something that is good at heavy multi-tasking. I usually have Lightroom, 3 different browsers, photoshop, rapidweaver, adium, and various other apps open at the same time.

Any help or input is greatly appreciated.
Thanks
 
None of the apps you mentioned are very CPU intensive so you should be fine with i5. If you have the $ for i7 and are ready to spend it, then you could pull the trigger. If nothing else, it will at least have better resale value and be more "future-proof" but it's not much faster than the i5
 

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Hellhammer said:
None of the apps you mentioned are very CPU intensive so you should be fine with i5. If you have the $ for i7 and are ready to spend it, then you could pull the trigger. If nothing else, it will at least have better resale value and be more "future-proof"
Click to expand...

I trust your knowledge when it comes to hardware specifics, but I'm a bit baffled, that PS and LR shouldn't take advantage of multiple cores. I only use two cores, but often see LR maxing out the CPU during its thing (rendering previews mostly). Wouldn't that be faster with more cores, or are LR and PS not able to use all 8 threads the i7 offers?
Do you have any insight in that?
 
Hellhammer said:
None of the apps you mentioned are very CPU intensive so you should be fine with i5. If you have the $ for i7 and are ready to spend it, then you could pull the trigger. If nothing else, it will at least have better resale value and be more "future-proof" but it's not much faster than the i5
Click to expand...

Thanks for pointing me to those benchmarks. Its cool to see how the different macs stack up to one another.
 
The way I saw it was that seven is two more than five, not sure if the i has any impact on it at all but as both have it then it must be even. :p



Sorry
 
spinnerlys said:
I trust your knowledge when it comes to hardware specifics, but I'm a bit baffled, that PS and LR shouldn't take advantage of multiple cores. I only use two cores, but often see LR maxing out the CPU during its thing (rendering previews mostly). Wouldn't that be faster with more cores, or are LR and PS not able to use all 8 threads the i7 offers?
Do you have any insight in that?
Click to expand...

Yeah Lightroom for me has always been a processor hog, especially when rendering 1:1 and standard previews from RAW files. Importing and Exporting all seem to tax the CPU too. Before my 06' MBP died it would take about 3-5 hours to export 300 photos, another 3hours just to render too. You have no idea how happy I am to get a new computer. LOL. I have heard that LR can take advantage of multiple cores but not virtual cores, I'll have to look that up.

Thanks for your input.
Zach
 
spinnerlys said:
I trust your knowledge when it comes to hardware specifics, but I'm a bit baffled, that PS and LR shouldn't take advantage of multiple cores. I only use two cores, but often see LR maxing out the CPU during its thing (rendering previews mostly). Wouldn't that be faster with more cores, or are LR and PS not able to use all 8 threads the i7 offers?
Do you have any insight in that?
Click to expand...

What I've heard, Photoshop is mainly single-threaded. Some of its features, e.g. rendering may be able to take advantage of extra cores but the clock speed is still more important.

19893.png


i7 performs ~15% faster in that test even though it has only ~10% higher clock speed so it looks like HT will give a minor boost in that specific task.

I've also heard that some applications do not benefit from the HT even though the extra "cores" should act like normal cores. Video encoding is a task that should max out the CPU usage but as you can see in the images below, i7 isn't much faster and it's faster due its clock speed.

19894.png


i7 is ~13% faster

19895.png


i7 is ~10% faster

19896.png


i7 is ~31% faster (first test where HT actually made difference)

It looks like LightRoom rendering can't use more than 8 threads at most, I would guess it can do up to 4.

HT seems to offer some extra in some tests but generally it won't help much, especially in Photoshop or LightRoom as they are quite poorly multithreaded. It may change in the future and thus i7 is always "a safe choice" but i5 is likely just fine.

It's hard to give exact answer is it worth it or not as for some tasks it is and for others it isn't. Some features is Photoshop and LightRoom may be able to take advantage of 4 threads while some task may be single-threaded so that will just make the case harder. Quite hard to find good Adobe CS benchmarks too.
 
Well it looks like I have finally decided on getting the iMac i7. Ill be ordering it tonight and can't wait for it to get here. All I have in the mean time is a lame HP dv2000. Thanks for all the input.
 
bigwig said:
Personally, I'd rather have the 3.6GHz i5 than the 2.9GHz i7.
Click to expand...

You do realize that the 3.6GHz i5 is DUAL core while the 2.9GHz i7 is a QUAD core processor right? The only quad core i5 Apple uses is the 2.8GHz in the high end iMac, and that is still worse than the i7.
 
Hisdem said:
You do realize that the 3.6GHz i5 is DUAL core while the 2.9GHz i7 is a QUAD core processor right?
Click to expand...
Right. For most workloads, including the OP's, the 3.6 is going to be significantly faster than the 2.9. Not only is most software not written to handle 4 cores, it can't be written to take advantage of 4 cores. Ergo, 2 fast cores is almost always better than 4 slower ones.

For a server, it's different. Four slow and cool cores are usually better than two fast cores, because the workload isn't compute intensive and you gain more with speed with the extra cores than you lose in locking contention.
 
The lynnfield 870 can get up to 3.6ghz core clock in single threaded tasks if it needs to anyways, so there really isn't much benefit to the 3.6ghz dual core clarkdale-- especially considering that down the line, more and more tasks will be efficiently coded for more threads. The lynnfield supports up to 8 threads while the clarkdale only supports up to 4. The most logical choice would to be either save the money and get a 3.2ghz i3 clarkdale or spend a little extra money and get the 2.93ghz lynnfield.
 
TMRaven said:
The lynnfield 870 can get up to 3.6ghz core clock in single threaded tasks if it needs to anyways, so there really isn't much benefit to the 3.6ghz dual core clarkdale
Click to expand...
Comparing a 2.93 GHz 4 core cpu that can boost a single core to 3.6 GHz to a dual core cpu where both cores run 3.6 and a single core can run 3.86 GHz isn't a very flattering comparison for the 4-core cpu with regard to non- or mildly-parallelizable tasks.
 
The lynnfields are known for their great turbo boost efficiency, because the amount of available bins they have access to is more than double that of the bloomfield and clarkdale line of chips. While in 1 core operations, the i7 series lynnfields have access to 5 bins of base frequency to dynamically overclock themselves, and the i7 lynnfields only lose 1 bin of headroom when in dual threaded mode, so that's 3.46ghz in dual core operation. The i5 clarkdale on the other hand only gains access to 2 speed bins while in 1 thread operation, and 1 bin per core while in dual thread operation (making for 3.73ghz)

Dual threaded process at 3.73ghz vs dual threaded at 3.46ghz for the sake of sacrificing potential futureproofing when more and more tasks become multithreaded? Sounds irrational to me.
 
Well thanks again for all the replies and input. I got my i7 iMac last Tuesday and am loving it so far. Lightroom & CS5 fly so much faster than my '06 2.0Ghz MBP. Screen is beautiful, it's quiet and multitasks well. I can already tell that I will need to upgrade the memory sometime soon since I have already maxed that out a couple of times. Just have to wait till I can afford it. I haven't even gotten close to maxing the processor though, I might have hit 80% when rendering photos.
 
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