Mac Musings

The 2010 iMac Value Equation

Dan Knight - 2010.07.28 - Tip Jar

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To quote the Beatles, "It's getting better all the time."

While much of the focus will be on the new high-end 12-core Mac Pro, the iMac has seen its share of significant improvements as well. All iMacs now use Intel's Core "i" technology and support HyperThreading, which means they can function as though they had twice as many cores. That's even true on the entry-level iMac with its 3.06 GHz Core i3 CPU.

The dual-core iMacs now use CPUs with 4 MB of Level 2 cache, up from 3 MB in the previous generation (quad-core CPUs still have 8 MB of L2 RAM), and Apple has moved from 1066 MHz memory to 1333 MHz RAM, further improving efficient data flow. Speeds now reach as high as 3.6 GHz for dual-core and 2.93 GHz for quad-core CPUs, and the dual-core iMacs officially support up to 16 GB of memory, twice as much as the units they just replaced.

In terms of graphics, it's a clean sweep for ATI - no Nvidia GPUs this time around, and no integrated graphics that ties up system memory. Then entry-level iMac has Radeon HD 4670 graphics with 256 MB of video memory, the faster 21.5" iMac and entry-level 27" iMac use Radeon HD 5670 graphics with 512 MB, and the top-end iMacs with quad-core CPUs have Radeon HD 5750 graphics with a whole gigabyte of video RAM.

Every iMac now supports HyperThreading, and the i5 and i7 also support Turbo Boost, which allows individual cores to run well beyond their rated speed.

21.5" iMacs

By way of comparison, the Late 2009 iMac used Intel's older Core 2 Duo CPU for the entry-level model, which had Nvidia GeForce 9400 integrated graphics, which used 256 MB of system memory, and ran at 3.06 GHz. At the same price point, the 3.06 GHz 21.5" 2010 iMac has a bigger Level 2 cache, a faster memory bus, and Radeon HD 4670 graphics with dedicated memory.

Although the CPU clock speed is the same as last year's entry-level model, the faster memory bus, bigger L2 cache, and discrete graphics processor will all contribute to improved performance, although we'll have to wait for benchmarks to see how great the difference is. Our guess is a 5% boost in overall CPU performance.

The faster 21.5" iMac, which normally has a 3.2 GHz i3 CPU, can also be ordered with a dual-core 3.6 GHz i5-680 CPU, believed to be the fastest dual-core processor ever made. This makes it the first 21.5" iMac to support Turbo Boost, which allows the computer to dynamically control the clock speed of each core. This allows it to run as fast as 3.86 GHz.

27" iMacs

The bigger iMac starts with a 3.2 GHz i3 and has the same 3.6 GHz i5 option as the faster 21.5" iMac, which means it can clock as high as 3.86 GHz. That compares favorably with the 3.06 GHz Core 2 Duo in last year's low-end 27" iMac, and the 3.2 GHz i3 should out perform it by 5-10%. The dual-core 3.6 GHz i5, with an 8% higher clock speed, should handily surpass last year's fastest dual-core iMac (3.33 GHz) even before Turbo Boost kicks in.

The real power comes in with the quad-core iMacs. The 2.8 GHz quad-core model's i5-760 CPU can Turbo Boost individual cores as high as 3.33 GHz, and the build-to-order 2.93 GHz quad-core i7-875 option can run cores at up to 3.6 GHz. Compare that to last year's top-end 2.8 GHz i7-860 CPU, which could Turbo Boost its cores to "only" 3.46 GHz. (Okay, that's only a 4% difference in clock speed, but it sure sounds fast.)

The Real World

Today's iMacs have more power than most of us will ever take advantage of. The same goes for last year's models. The level of processing and graphics power will satisfy hard core gamers and people who do a lot of video work; for anyone else, more than adequate.

I'm going to have to assume that you are a power use if you're looking beyond the entry-level models, so you have a real need for lots of processing power, most likely doing some sort of processor intensive production work. That is, you are one of those people who needs more than two 3.06 GHz cores with HyperThreading.

The 2010 Lineup

  • 21.5" 3.06 GHz i3, $1,199
  • 21.5" 3.2 GHz i3, $1,499
  • 21.5" 3.6 GHz 2-core i5 BTO, $1,699
  • 27" 3.2 GHz i3, $1,699
  • 27" 3.6 GHz 2-core i5 BTO, $1,899
  • 27" 2.8 GHz 4-core i5, $1,999
  • 27" 2.93 GHz 4-core i7, $2,199

Let's assign relative power ratings, giving the 3.2 GHz i3 a nominal rating of 100. The entry-level 3.06 GHz model rates 95, a relatively insignificant difference. For $300 less (a 20% lower price), from the standpoint of power per dollar spent, the entry-level model is a hands-down winner.

My best guess is that the 3.6 GHz dual-core i5 rates at 116, assuming it averages 3.73 GHz (the halfway point between base speed and maximum core speed) thanks to Turbo Boost. You're paying a 13% premium for the faster CPU on the 21.5" iMac and 12% more on the 27" model. This makes the 3.6 GHz build-to-order option the better choice from a performance-per-dollar perspective.

Things get quite a bit trickier with quad-core CPUs, as the maximum clock speed only applies to one or at most two cores. That gives the 2.8 GHz quad-core i5 a rating of 185 or so. The cost premium is just under 18% compared with an 80% (or so) boost in power. A no-brainer for those who need raw power.

At the top, I'd estimate a 195 to 200 score for the 2.93 GHz quad-core i7. That's roughly double the power of the 3.2 GHz model at a 30% increase in price. Not a bad deal, but overall the quad-core i5 is the power-per-dollar winner in the new iMac line.

Last Year's Models

Here are the best close-out and refurbished prices I could find for the just-discontinued iMacs:

  • 21.5" 3.06 GHz Nvidia, $999
  • 21.5" 3.06 GHz Radeon, $1,269
  • 21.5" 3.33 GHz Radeon, $1,349
  • 27" 3.06 GHz 2-core, $1,369
  • 27" 3.33 GHz 2-core, $1,599
  • 27" 2.66 GHz 4-core i5, $1,699
  • 27" 2.8 GHz 4-core i7, $1,849

The new 3.06 GHz i3 model at $1,199 is a better deal than last year's 3.06 GHz Core 2 Duo model with Radeon graphics at $1,269, but the 3.33 GHz close-out model at $1,349 could be very tempting.

At the 27" size, $1,369 for a close-out 3.06 GHz Core 2 Duo model is an excellent deal, as the least expensive 2010 model at this size is $1,699. The 3.33 GHz 2009 model is also well priced at $1,599 - still $100 below the new entry level. Moving up to the quad-core models, close-out pricing is once again compelling.

At these prices, the close-out 2009 iMacs are the better value except for the 3.06 GHz 21.5" Radeon model. At that price point, the brand new 3.06 GHz i3 model is the value champion. LEM

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Dan Knight has been using Macs since 1986, sold Macs for several years, supported them for many more years, and has been publishing Low End Mac since April 1997. If you find Dan's articles helpful, please consider making a donation to his tip jar.

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