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Apple’s 24″ iMac: There’s more to High End than Performance

Last April, Apple got our attention with a Core Duo 17″ iMac that was the quietest, most efficient stock system we’ve seen from a major brand. The iMacs now sport Intel’s Core 2 Duo chips. Apple has introduced a new version with a massive 24″ screen that will impress even those who don’t follow technology closely. A few extra FPS from the latest 8800GTX is one thing, but massive LCD screen is a much more visible status symbol. Yes, the iMac is much about image. But we’re sure to like it if it can match the noise performance of its predecessor.

November 20, 2006 by Devon

Apple 24″ iMac
Selling Price
~US$2,000 from the Apple

Apple’s integrated laptop-parts-built-into-a-screen approach to their recent
iMacs has done much to bring quiet computing to the masses. We know. We
looked at a 17″ iMac last April
that was one of the coolest, quietest,
most efficient computers that we’ve ever laid eyes on.

Time has rolled on since then, and Apple has made the inevitable iMac upgrade
to Intel’s Core 2 Duo chips. They have also introduced a new 24″ iMac model
that seems poised to push the iMac into the higher end. Judged only on the basis
of the hardware inside, the 24″ iMac is still a midrange machine. Core
2 Duo may be cutting edge, but 1 GB of RAM is standard these days, and the 250
GB hard drive and the GeForce 7300GT are far from high end.

Then again, Apple’s criteria for what constitutes “high end” are
closer to those used by the automotive industry than the tech industry. Luxury
cars are sold mostly on image, not performance, and that is exactly what
the 24″ iMac is selling. A 24″ screen looks impressive, no
matter what hardware is running on it. And, given how little difference there
is in user experience between a fast Core 2 Duo and a lowly Sempron, the larger
monitor may be a better investment.

Obviously, the tiny minority of users who actually have a use for a high clocked
CPU will not find their needs met by an iMac. Ditto the larger minority who
play enough games to notice the difference between a high end GeForce 8800GTX
and nVidia’s entry level GeForce 7300GT. Those who equate the high end with
raw performance will probably be not be interested in an iMac.

But, given what most people use their computers for — internet and e-mail,
business applications, watching movies and listening to music, occasional gaming
— building a high end machine around performance doesn’t make sense.
There just isn’t enough difference in usability, so why not spend the money
on features that will be noticed. The iMac offers some unique and unusual features
that help create a high end feel that is easily noticed without running
benchmarks. Among them:

  • A large, built-in 24″ LCD screen
  • A fully integrated design with no separation between the screen and the
    rest of the computer
  • Fewer cables to connect
  • OS X and its impressive number of integrated applications
  • Apple’s elegant image and style

Of course, that list is missing two features that are very important to readers
of this site: Noise and power efficiency. These are the things that make a system
high end for SPCR. Is the 24″ iMac high end? Our experiences with the 17″
and 20″ iMacs have made us hopeful, but can the 24″ model live up
to the tough standard that was set by it’s smaller brothers?

Flat panel or not, a 24″ screen occupies a lot of desk real estate.


Integrated it may be, but the iMac is not lacking for features, including a
few that are far from common on the PC side of things. Wireless networking,
Bluetooth support and a remote control for media playback are all nonstandard
features for mainstream desktop systems. Widespread adoption of the USB 2.0
and Firewire interfaces make it easy to add any peripherals that are missing.

The exact specifications are somewhat flexible; Apple allows a certain amount
of hardware customization when you order. Heavy multimedia users will probably
want to spring for a bigger hard drive — 500 GB and 750 GB options are
available as upgrades over the basic 250 GB model. Gamers may also want to bump
the graphics card up to a GeForce 7600GT… and download Boot Camp so that Windows
can be used.

One thing that irked us was the lack of office software: Trial versions
of both iWork ’06 and Microsoft Office 2004 are included, but Apple expects
you to pony up another US$80 for the full version of iWork. The presence of
trial software is almost worse than having nothing at all. Two preinstalled
pieces of software that are unusable without paying extra doesn’t do much for
Apple’s “fully integrated” approach.

That aside, we appreciated the scope of the software that is included. In combination
with the iLife suite, OS X offers several pieces of software that go above and
beyond what is included with Windows XP, including:

  • Apple DVD Player
  • Xcode Developer Tools (for writing software)
  • iDVD (DVD authoring)
  • iWeb (for building internet content)
  • GarageBand (audio recording & editing)
  • Front Row (HTPC software for use with the Apple Remote)
Apple 24″ iMac Specifications
(Note: Our sample was the base model.)
In the Box
– iMac
– Apple Keyboard
– Mighty Mouse
– Apple Remote(1)
– Power cord
– Install/restore DVDs
– Printed and electronic documentation
– 2.16GHz Intel Core 2 Duo processor (T7400) w/ 4MB
shared L2 cache
– 667MHz system bus
– 1GB (2x512MB) of PC2-5300 (667MHz) DDR2 memory
– Two SODIMM slots support up to 3GB
– 250GB Serial ATA 7200-rpm hard drive (Seagate ST3250824AS)
– 8x SuperDrive (DVD+R DL/DVD±RW/CD-RW)
– Built-in 54-Mbps AirPort Extreme Card (802.11g standard)
– Built-in Bluetooth 2.0+EDR (Enhanced Data Rate) module
– Built-in 10/100/1000 BASE-T Gigabit Ethernet (RJ-45 connector)
– Built-in 24-inch (viewable) widescreen TFT active-matrix
liquid crystal display
– Millions of colors at all resolutions
– Typical viewing angle: 178° horizontal, 178° vertical
– Typical brightness: 400 cd/m
– Typical contrast ratio: 700:1
Graphics and Video
– NVIDIA GeForce 7300 GT graphics processor with 128MB of GDDR3 SDRAM
using PCI Express
– Mini-DVI output port with support for DVI, VGA, S-video, and composite
video connections via adapter
– Built-in iSight camera
– Support for external display in extended desktop
* Digital resolutions up to 1920 x 1200
* Analog resolutions up to 2048 x 1536
– Support for external display in video mirroring mode
Electrical and environmental requirements
– Meets ENERGY STAR requirements
– Line voltage: 100-240V AC
– Power cable Frequency: 50Hz to 60Hz, single phase
– Maximum continuous power: 220W
– Operating temperature: 10° to 35° C (50° to 95° F)
– Storage temperature: -40° to 85° C (-40° to 185° F)
– Relative humidity: 5% to 95% noncondensing
– Maximum altitude: 10,000 feet
Size and Weight
– Height: 52.3 cm (20.6 inches)
– Width: 57.4 cm (22.6 inches)
– Depth: 20.7 cm (8.1 inches)
– Weight: 11.2 kg (24.7 pounds)
Peripheral Connections
– One FireWire 400 and one FireWire 800 port; 15 watts
– Total of five USB ports: three USB 2.0 ports (up to 480 Mbps) on computer,
two USB 1.1 ports on keyboard
– Built-in stereo speakers
– Internal 24-watt digital amplifier
– Headphone/optical digital audio output (minijack)
– Audio line in/optical digital audio input (minijack)
– Built-in microphone
– Mac OS X v10.4 Tiger (includes Spotlight, Dashboard,
Mail, iChat AV, Safari, Address Book, QuickTime, iCal, DVD Player, Xcode
Developer Tools)
– iLife ’06 (includes iTunes, iPhoto, iMovie HD, idvd, iWeb, GarageBand),
Microsoft Office 2004 for Mac Test Drive, iWork (30-day trial), Big Bang
Board Games, Comic Life, Omni Outliner, and Apple Hardware Test
– Front Row
– Photo Booth

One thing that gave us pause was the power rating: The 24″ model is rated
for a maximum of 220W, while the smaller models are rated for 180W. That’s unfortunate;
it suggests the system will not be as efficient as the 17″ model that we
saw before. That could pose a problem for noise if the extra power is concentrated
enough to cause overheating. Hopefully, its larger size will help dissipate
the extra heat.

Another oddity was the system bus speed — 667MHz instead of the standard
1066MHz. The explanation is that Apple is using the mobile version of
the Core 2 Duo (our sample had a T7400), which still uses 667MHz as its bus
speed. This bodes well for power consumption, since mobile parts are typically
more efficient than desktop parts, but performance enthusiasts will no doubt
be disappointed.


The 24″ iMac is BIG. This wasn’t apparent until we sat down in front of
it and actually started using it, but it was big enough that we needed to sit
back from it a bit to see the whole screen. The 1,920 x 1,200 pixel desktop
leaves a lot of room for multiple applications, especially text-based ones where
text columns typically occupied less than half of the screen’s width. One small
complaint that we had was that the high resolution made the mouse seem very
slow. Even with the pointer speed turned up to maximum, moving the pointer across
the screen required almost a foot of lateral movement with the mouse —
too much to stay on a mouse pad without using multiple motions.

The 24″ screen provides a lot of desktop area.

The thermal design is more or less the same as the
17″ iMac
that we looked at last April. A large intake vent runs along
the bottom edge of the screen, while an elegant slit at the top of the back
panel serves as an exhaust. There are undoubtedly cooling fans inside, but they
spin slowly enough that hot air that escapes trickles out not much faster than
the speed of natural convection.

The intake vent on the bottom is invisible unless you’re looking for it.

The exhaust vent is also well hidden. (It’s the white strip along the top).

Like the 17″ iMac, the 24″ model uses a slot-loading optical drive
mounted into the right edge of the screen. We like the fact that it’s well hidden,
but it would be nice to have a physical button to eject the disc, as the eject
key on the keyboard only works when the operating system is loaded. In fact,
we ran into an interesting puzzle when we used Boot Camp to install Windows:
Once Windows is installed, a separate disc is needed to install the iMac-specific
drivers. This requires changing discs… but the eject key on the keyboard doesn’t
work without special drivers installed. The solution, of course, is to track
down the software eject function, which is buried in a context menu — hardly
an intuitive solution.

On the same note, it would also be nice to have some control over the LCD functions
that aren’t software based. The intensity of the backlight can be adjusted with
a special option in System Preferences, but other common functions like contrast,
color temperature and color correction must be done by adjusting the signal
generated by the graphics card instead of fixing it on the screen itself. Admittedly,
the disadvantages of this method are only likely to be noticed by a small portion
of iMac customers, but it still seems an odd approach given Apple’s popularity
among visual design professionals.

The back is as stylish as the front.

The output ports keep things small and simple: One jack for sound output, one
for sound input, three USB 2.0 jacks (plus two USB 1.1 jacks built into the
keyboard), and one each for Firewire 400 and 800, ethernet, and dual link mini-DVI
port. This is more than enough for everyday use, but users with lots of peripherals
may find themselves shelling out for various adapters such as USB hubs, mini-to-full
DVI dongles, and Apple’s unusual optical mini plug for multichannel audio.

A neat line of external connectors, including one Firewire 800 port.


The 24″ iMac was tested twice: Once in OS X and once in Windows using
our standard test tools. Unlike our test of the 17″ iMac, these tests did
not reveal any thermal or efficiency differences between the two operating systems,
although the more robust power saving features in OS X do more for saving power
than the default options in Windows.

The following software was used during testing:



Power consumption was measured with a Seasonic Power Angel, and noise
was measured with our usual B&K 2203 SLM.

Ambient conditions at the time of testing were 18 dBA and 21°C.

iMac: OS X
Activity State
Noise Level
CPU Temperature
AC Power Draw
Idle (LCD off)
20 dBA@1m
Idle (LCD dimmed)
20 dBA@1m
Idle (LCD on)
20 dBA@1m
2 x CPUBurn
20 dBA@1m
CD Burn @ 24x
30 dBA@1m
CD Read @ 16x
24 dBA@1m
HDD Seek
21~22 dBA@1m

The 93W that the 24″ iMac ate up at idle was a far cry from the 46W that
the 17″ model used when we tested it. A whopping two thirds of this power
is consumed by the LCD screen, which is significantly brighter (400 CD/m vs.
250 CD/m) and more contrasty (700:1 vs. 500:1) as well as being larger than
the 17″ model. With the LCD screen in standby, the remaining components
required just 31W — less than any desktop system we’ve built for ourselves,
and, significantly, approximately the same amount required by the 17″ iMac,
despite the differences in hardware.

Things got better when the LCD dropped into low power mode by reducing the
brightness to the lowest level possible. The amount of power consumed by the
LCD dropped by almost half to about 34W, now about 50% of the total system power.
However, the automatic use of this function sometimes got quite irritating,
since the low power mode sometimes kicked in while reading a large block of
text on a web page and the mouse would have to be moved around to boost the
brightness back up. Given how vibrant the display is by default, the best solution
is brightness down all the time.

If the system was left alone for much longer — about 15 minutes —
the system would shut itself down into standby mode, where the total power consumption
dropped to just three watts. Our experience has generally been that standby
mode is more stable and reliable in OS X than in Windows, but that doesn’t get
around the fact that its not 100% reliable at detecting idle behavior. We had
to disable the standby feature during testing because the system kept shutting
down while we were running CPUBurn.

With CPUBurn going, power consumption jumped up about 30W — pretty much
what we expected of the new Core 2 Duo chips, but almost twice as required by
the Core Duo-based iMac that we saw. The processor quickly heated up to a toasty
66°C at full load. That’s hot but not too hot, and we were pleased to note
that the noise level never increased — it stayed at a barely noticeable
20 dBA@1m no matter how we stressed the system.

The noise character was the same unintrusive background hum that the 17″
iMac exhibited. From memory, it seemed very slightly more noticeable, but we
weren’t able to measure a difference. Perhaps the difference is the hard drive;
the 24″ model used a Seagate instead of a Maxtor. In any case, then noise
was quiet, easy to ignore, and didn’t change during use. That’s exactly what
we expect of a quiet computer, and, despite the additional heat from the LCD
screen, the 24″ iMac delivered.

One thing we noticed was that the system seemed to be a bit louder when placed
against a wall, presumably because the wall reflected the noise coming off the
back of the system. This was confirmed with a measurement: The system measured
21 dBA@1m when moved within twenty centimeters of the back wall in the lab.

The noisiest the iMac ever got was when the optical drive was in use. Burning
at 24x was quite noisy, but the noise character was surprisingly benign: Mostly
the whoosh of airflow with a little bit of whine underneath. It sounded decidedly
less harsh than the conventional drives that we are used to, most likely because
the plastic casing of the iMac provides a bit of damping. Unfortunately, it
did a poor job of damping the thunderous seek noise, which actually sounded
more intrusive at 24 dBA@1m than the smooth burning at 30 dBA@1m.

The hard drive in our sample was a Seagate, so we were expecting noisy seeks,
but the seek noise was surprisingly muted — it sounded less sharp than
Seagate’s drives sound in free air. The 1~2 dBA@1m rise above the baseline noise
accurately captures what we heard: Seeks were clearly audible, but they weren’t
especially loud.

iMac: Windows XP
Activity State
Noise Level
CPU Temperature
GPU Temperature
AC Power Draw
Idle (SpeedStep)
20 dBA@1m
20 dBA@1m
2 x CPUBurn
20 dBA@1m
Intel TAT
20 dBA@1m
Intel TAT + ATI Tool
20 dBA@1m

Thermal and acoustic performance in Windows was exactly the same as in OS X,
so it merits no more comment. However, running in Windows did allow us to try
one additional test with Intel’s (technically unreleased) Thermal Analysis Tool.
In addition to being able to monitor core temperature and throttling on Core
2 Duo chips, this tool does a better job of stressing the CPU than any other
utility that we know of.

With the help of this admittedly unrealistic test, we were able to push power
consumption up another 13W. The CPU temperature climbed to a toasty 75°C
at this level, but even at this level the noise level never increased. We left
the system burning in this way for over an hour, but the system was perfectly
stable and the processor did not throttle. We can only conclude that, hot as
it was, it never reached unsafe levels.

One thing that running in Windows did let us do was to monitor the GPU temperature.
Surprisingly, the GPU seemed more affected by what the CPU was doing nearby
than any graphics load we could come up with. Hence, the 20°C difference
between idle and full CPU load, but the 0°C difference when we threw ATI
Tool’s artifact detector into the mix. We can only conclude that the mobile
7300GT chip doesn’t produce enough heat to worry about. In any case, the GPU
temperature was always below the CPU temperature, so we have no worries about
its longevity in the iMac.


Each of these recording have 10 seconds of silence to let you hear the ambient
sound of the room, followed by 10 seconds of the product’s noise.

Sound Recordings of Comparative Systems


  • Shuttle X100 — Idle / Load (Fan on): 25 dBA@1m: One
    , One

    These recordings were made
    with a high resolution, studio quality, digital recording system, then
    converted to LAME 128kbps encoded MP3s. We’ve listened long and hard
    to ensure there is no audible degradation from the original WAV files
    to these MP3s. They represent a quick snapshot of what we heard during
    the review. Two recordings of each noise level were made, one from a
    distance of one meter, and another from one foot

    The one meter recording
    is intended to give you an idea of how the subject of this review sound
    in actual use — one meter is a reasonable typical distance between
    a computer or computer component and your ear. The recording contains
    stretches of ambient noise that you can use to judge the relative loudness
    of the subject. For best results, set your volume control so that the
    ambient noise is just barely audible. Be aware that very quiet subjects
    may not be audible — if we couldn’t hear it from one meter, chances
    are we couldn’t record it either!

    The one foot recording is
    designed to bring out the fine details of the noise. Use this recording
    with caution! Although more detailed, it may not represent how the subject
    sounds in actual use. It is best to listen to this recording after you
    have listened to the one meter recording.

    More details about how
    we make these recordings can be found in our short article: Audio
    Recording Methods Revised


    We liked the first iMacs we saw, and very little has changed with the 24″
    model so we like it as well. It remains one of the quietest off-the-shelf systems
    it is possible to buy and, with a built-in 24″ screen, it offers fairly
    good value-for-money. A similarly configured Dell system that we looked at was
    only about US$200 cheaper, and it lacked the integration and style that are
    Apple’s hallmarks.

    It is also fairly efficient, although the large LCD prevented it from being
    as frugal as the 17″ model. In fact, the LCD consumed the lion’s share
    of the power — well over half when the system was idle. We’re not sure
    how this falls in with other large LCD screens on the market, but it certainly
    consumed more than the 17~19″ screens that we’ve measured, which typically
    require 25~35W. Discounting the LCD, the system was on par with the 17″
    iMac at idle, and only slightly more power hungry under load.

    Is the higher power consumption a fair price to pay for the larger screen?
    Well, that’s up to you, but we can certainly think of worse ways to consume
    power. The larger screen is potentially much more useful than, say, a faster
    processor or a high end motherboard. That’s not to say that high performance
    components don’t have their place, but most users — especially those who
    would buy an iMac — will probably see more benefit from a bigger screen
    than a higher clocked processor.

    Besides, the iMac is far from a slouch. Intel’s Core 2 Duo provides oodles
    of power, and the iMac was as speedy as any system we’ve used. Performance purists
    will no doubt complain that performance is bottlenecked by the slow FSB that
    goes with the mobile processor, but we noticed no performance hit. We just lament
    the fact that Apple is charging extra for a faster processor that won’t be used.

    All in all, the iMac is a high end product that the masses will understand.
    It’s luxurious status comes from its image and integration, not performance.
    Thankfully, low noise is part of that image, and we like it for that all the

    Much thanks to Apple
    for supplying the 24″ iMac sample for us to review.


    SPCR Articles of Related Interest

    Apple iMac w/Intel Core Duo:
    A User’s Review

    Fanless Ultra Powerhouse PC by EndPCNoise
    17″ iMac —
    The Official SPCR Review

    Puget Delivers a Quiet Core
    Duo PC

    * * *

    this article in the Silent PC Review Forums.


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