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smirk

macrumors 6502a
Original poster
Jul 18, 2002
691
54
Orange County, CA
Hi, I'm trying to decide between the i5 and i7 iMac. I realize that the aluminum back acts as a heat sync, but can anyone comment on how warm the computer makes your room? I used to have a halogen floor lamp in my room and after an hour or so the room got noticeably warm and I'd have to open a window. Does either model of iMac throw off enough heat to do that?

Thanks!
 

TMRaven

macrumors 68020
Nov 5, 2009
2,099
1
Ironically enough it doesn't heat up my room as much as the old G5 iMac did, and I think the i7 iMac consumes more watts as well. Combine the i7 iMac with a tube amp headphone amplifier next to it, and my room can get rather toasty.
 

Icaras

macrumors 603
Mar 18, 2008
6,344
3,393
Ironically enough it doesn't heat up my room as much as the old G5 iMac did, and I think the i7 iMac consumes more watts as well. Combine the i7 iMac with a tube amp headphone amplifier next to it, and my room can get rather toasty.

Would you happen to know the maximum amount of watts used between the i5 and i7 processors? Also, in single threaded applications, or on just normal usage, would the i7 run as cool as the i5?
 

Voondebah

macrumors member
Mar 28, 2010
75
1
2.5/2.7 GHz i5 or 2.8 GHz i7 => 65W TDP
3.1 GHz i5 or 3.4 GHz i7 => 95W TDP


I Have a base 27" (2.7 GHz i5), and for normal use (web browsing, email, netflix), the top of the aluminum case is warm but not hot. I haven't noticed my room feeling any noticeable amount warmer than before when I was using a mac mini.

Certainly could be different results depending on how intense your workload is.
 

johnfkitchen

macrumors regular
Sep 7, 2010
210
0
The specs say "Maximum continuous power: 205W (21.5-inch models); 310W (27-inch models)"

So you are looking at two or three light bulbs if you work your iMac continuously with all cores and GPU hard at work. A lot less than that in practice.

Source:- http://www.apple.com/imac/specs.html
 

TallManNY

macrumors 601
Nov 5, 2007
4,742
1,594
Normal use (i.e., web browsing and word processing) result in just a warm top on my new i5. Game playing results in it getting hotter, but nothing series as far as I can tell. Certainly not like a radiator.
 

Icaras

macrumors 603
Mar 18, 2008
6,344
3,393
The specs say "Maximum continuous power: 205W (21.5-inch models); 310W (27-inch models)"

So you are looking at two or three light bulbs if you work your iMac continuously with all cores and GPU hard at work. A lot less than that in practice.

Source:- http://www.apple.com/imac/specs.html

Yes, but the question is between an i5 and an i7, which both exist on both 21.5" and 27" models. We can fairly assume that the i7 processors will reach those numbers on the specs but I'm curious about the wattage differences between processor configurations.
 

alust2013

macrumors 601
Feb 6, 2010
4,779
2
On the fence
Yes, but the question is between an i5 and an i7, which both exist on both 21.5" and 27" models. We can fairly assume that the i7 processors will reach those numbers on the specs but I'm curious about the wattage differences between processor configurations.

All the wattages on the 21.5" are the same. The base 27" is the same as the 21.5", and the higher end i5 and i7 27" are higher wattage. The i7s may have slightly higher actual usage as compared to their i5 counterparts, but not enough for a physical heat difference.
 

dwarnecke11

macrumors 6502
Nov 29, 2009
354
0
My 2010 i7 iMac runs very cool. According to iStat, the CPU idles around 39° C, one of the coolest parts of the machine usually.
 

MrT-Man

macrumors regular
Jan 22, 2008
127
25
The specs say "Maximum continuous power: 205W (21.5-inch models); 310W (27-inch models)"

So you are looking at two or three light bulbs if you work your iMac continuously with all cores and GPU hard at work. A lot less than that in practice.

Source:- http://www.apple.com/imac/specs.html

You can't compare it to light bulbs because that assumes that a CPU, GPU etc. shed as much heat as a % of their power consumption as a light bulb does, and I don't think that's a valid assumption.
 

MacVibe

macrumors regular
Dec 21, 2009
201
3
You can't compare it to light bulbs because that assumes that a CPU, GPU etc. shed as much heat as a % of their power consumption as a light bulb does, and I don't think that's a valid assumption.

It is a valid assumption since it is all going to be heat eventually even though the machine does some useful things in the meantime. At steady state the heat from a 180 W computer is the same as the heat from 3 60 W light bulbs.
 

Badger^2

macrumors 68000
Oct 29, 2009
1,962
2
Sacramento
It is a valid assumption since it is all going to be heat eventually even though the machine does some useful things in the meantime. At steady state the heat from a 180 W computer is the same as the heat from 3 60 W light bulbs.

Are we taking 3 60 watt *normal* bulbs or 3 60 watt CFLs?

Sadly, normal bulbs expend nearly 80% of their energy via heat.

Computers do not.
 

MacVibe

macrumors regular
Dec 21, 2009
201
3
Are we taking 3 60 watt *normal* bulbs or 3 60 watt CFLs?

Sadly, normal bulbs expend nearly 80% of their energy via heat.

Computers do not.

By definition, the power ratings are wall electric, and all this electricity goes into heat.

A 60 W CFL will give of 2.5 times as much light as a 60 W *normal* (incandescent) bulb but they will both give off 60 W of heat. Next time you buy a CFL, if you look closely, you will find the "60 W" value they list as an equivalency, but they will also list the actual power usage, perhaps about 23 W.
 

imahawki

macrumors 6502a
Apr 26, 2011
612
8
My 3.4GHz i7 can make my den hotter than the rest of the house when converting several movies in a row with Handbrake, but not under normal load usage.
 

Icaras

macrumors 603
Mar 18, 2008
6,344
3,393
All the wattages on the 21.5" are the same. The base 27" is the same as the 21.5", and the higher end i5 and i7 27" are higher wattage. The i7s may have slightly higher actual usage as compared to their i5 counterparts, but not enough for a physical heat difference.

I already know they are the same wattages on the 21.5" models and base 27". What I'm saying is, that I think it's fair to assume that the i5 will not ever reach the 65 watt limit and that spec is for the i7 processor. What I'd like to know basically, is what is the maximum wattage for the i5 processor.

Do all of you people live in blast furnaces?

Or in some 3rd world country without AC? :p

You can say that. ;) For some people, it may not just be a question about having AC or not, but also about racking up that electricity bill too. For some unfortunate like me, at about noon time until evening, the sun is always facing my room, pretty much roasting it all day. I have gone from a Mac Pro to an iMac and I can tell you the differences in wattages can be a huge difference in affecting room temperature, which is why for me, I try to pay close attention to wattage ratings...I'm also happy that Apple is such a green company in trying to minimize carbon footprints on their machines and are rated amongst some of the best energy efficient computers in the industry.

Oh, and some third world countries have cities that are more standardized with AC than some cities in 1st world and 2nd world countries do. It all depends on the respective regional climates obviously.
 

smirk

macrumors 6502a
Original poster
Jul 18, 2002
691
54
Orange County, CA
Awesome, thanks everyone for your answers. I was curious what I'd be in for when I get my new iMac and now it seems cooking the room won't be an issue.
 

bniu

macrumors 65816
Mar 21, 2010
1,120
303
Oh, and some third world countries have cities that are more standardized with AC than some cities in 1st world and 2nd world countries do.

not hard to believe at all. Third world countries have the advantage of not needing to replace existing infrastructure, so it's quite easy for them to go from nothing to top of the line. It's why Mongolia has a much more modern air traffic control system than the US does. Just like how people who jumped onto the iPad bandwagon this year with iPad 2 have a much better iPad than the early adopters from last year...:D
 

MMbassist

macrumors newbie
Dec 24, 2010
6
0
Charleston SC
I don't know very much about the amount of heat a mac gives off, but it's really not much. I do know a lot about heating and cooling because thats what I do for a living. Your computer would have to give off a ton of heat to raise the heat in your room. I'm pretty sure that floor lamp gave off more heat than the computer will. My guess is that it's not even your lamp that was really giving off to much heat. Heat travels toward cold, if that room has a wall facing the outside of the house the heat from it and the attic will actually come inside the room because it's usually at a lower temperature than the outside air. Obviously if you add any more objects that give off heat, the heat content will rise in that room. The only way to completely avoid it is to turn on the AC, and sit in the dark in that room, or you could just put a fan in there to help circulate the air and make it feel cooler.
 

mrfoof82

macrumors 6502a
May 26, 2010
577
15
Lawton, OK
Here's some actual power consumption numbers for a fully-loaded 27" iMac (3.4GHz i7, 16GB RAM, 256GB SSD+2TB HDD, 6970M 2GB VRAM) *and* a 27" LED Cinema Display. An Apple Wired Keyboard is plugged in, an iPhone 4 is plugged in and charging, it's connected via 802.11n, and bluetooth is enabled (Magic Mouse or Razer Orochi).

iMac only, basic use, 50% brightness: 95W.
iMac and display, idle, 50% brightness: 120W.
iMac and display, basic use, 50% brightness: 145W.
iMac and display, compiling and light gaming, 50% brightness: 180W.

These measurements are consistent from both an APC Back-UPS RS700 and a P7 Kill-a-watt.

I haven't measured, but I assume heavy gaming is more around 210-220W for the full load (again, including a display here). This is still less than a Core2 Duo gaming PC with an nVidia 8800GT I built back in 2007, with a 23" HD Cinema Display hooked up under similar conditions (heavy gaming).
 
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