The 2008 Penryn iMac Value Equation

Apple refreshed the iMac line yesterday, and although the new iMacs look just like the old ones, there are quite a few changes under the hood.

The biggest change is going to the new Penryn Core 2 Duo CPU, which is more energy efficient, has a larger (6 MB) level 2 cache, and runs on a 1066 MHz system bus (vs. 800 MHz in last year's model). Penryn also includes Intel's SSE4 instruction set, which further improves some processes (SSE is Intel's equivalent of AltiVec).

To top that off, all except the base model now include 2 GB of RAM, and the 24" iMac can be ordered with an Nvidia GeForce 8800 GS graphics processor. And CPU speeds now range from 2.4 GHz to 3.08 GHz, a nice step up from 2.0-2.8 GHz in the 2007 line.

In terms of value, the 20" 2.4 GHz, 20" 2.66 GHz, and 24" 2.8 GHz models retail for the same prices as their predecessors, and the 24" 3.06 GHz model, which has the Nvidia graphics, lists at $100 less than the old 2.8 GHz iMac. (To the best of our knowledge, the new 20" Penryn iMacs use the same 18-bit color display as last year's model.)

Penryn vs. Santa Rosa

The MacBook and MacBook Pro moved to Penryn in February, so we already have some comparison benchmarks to tell us how much more efficient Penryn is compared to the previous generation Core 2 Duo CPU. Testing the 15" MacBook Pro (2007 2.4 GHz with 4 MB L2 cache, 2008 2.4 GHz with 3 MB L2 and 2.6 GHz with 6 MB L2), Bare Feats found that the 2.4 GHz Penryn with its 3 MB cache (the version used in the new iMacs has 6 MB) beat the 2.4 GHz Core 2 with its 4 MB cache in 2 of 3 benchmarks. The 2.6 GHz Penryn, with both a faster CPU speed and a larger L2 cache, won all four benchmarks (one wasn't run on the 2008 2.4 GHz MacBook Pro).

These are real world benchmarks, not artificial ones (like the generally useful ones from Primate Labs), and if we normalize the 2.6 GHz results to approximate a 2.4 GHz CPU, we find Penryn 19% faster on the Compressor benchmark, 8% faster on Photoshop, 7.4% on After Effects, and 5% faster on QuickTime. Based on this, we can project that Penryn will generally be 5-10% more powerful at the same processor speed - and the Penryn MacBooks don't have the benefit of a 1066 MHz system bus.

We can predict that the 3.06 GHz Penryn will outperform the older 2.8 GHz Core 2 Duo by approximately 15-20%, the 2.8 GHz Penryn will beat last year's 2.4 GHz CPU by about 25%, the 2.66 GHz edge out the 2.4 GHz by almost 20%, and the 2.4 GHz trounce the old 2.0 GHz CPU by nearly 30%. These are the numbers we'll use in comparing value.

The Contenders

I updated our iMac price tracker this morning. Here are the best prices I found on the 2007 and 2008 iMacs:

• 20" 2.0 GHz (2007), $1,049 after rebate
• 20" 2.4 GHz (2007), $1,219 after rebate
• 20" 2.4 Ghz (2008), $1,144 after rebate
• 20" 2.66 GHz (2008), $1,419 after rebate
• 24" 2.4 GHz (2007), $1,494 after rebate
• 24" 2.8 GHz (2008), $1,694 after rebate
• 24" 3.06 GHz (2008), $2,094 after rebate

2.8 vs. 3.06 GHz

At the top, the 3.06 GHz iMac provides about 9% more processing power than the 2.8 GHz Penryn model. It also has superior graphics (Apple says about 2.2x as fast) and a 500 GB hard drive vs. 320 GB in the slower model. For that, you pay about 23% more.

As build-to-order options, Apple charges $200 for the faster CPU, $50 for the larger hard drive, and $150 for the Nvidia graphics card. For the 9% faster CPU, you pay an 11% premium. We can't fault the value there. And for serious gamers, the Nvidia card is probably worth the $150 price. That said, high-end gaming has become far more graphics intensive than processor intensive, so the best value for gamers is probably the 2.8 GHz model with the graphics upgrade - and the best value for power users who don't do gaming is probably the 3.06 GHz CPU with the base Radeon graphics card.

2.8 vs. 2.4 GHz

We've estimated that the 2.8 GHz Penryn iMac has 25% more processing power than the 2.4 GHz Core 2 in the 2007 iMac, but you only save about 12% by choosing the close-out 2007 24" iMac vs. the new Penryn. For us, it's a no brainer - buy the new one.

20" iMacs

We project the 2.66 GHz Penryn iMac will average 20% more processing power than last year's 2.4 GHz iMac, which sells for 14% less. Advantage Penryn.

Comparing the 2.66 GHz and 2.4 GHz Penryn iMacs, we estimate 11% more processing power, not enough to justify the 24% price premium even taking into account the bigger hard drive (320 GB vs. 250 GB) and an extra gigabyte of RAM (about $40 on the open market). Bang for the buck, the new entry-level iMac wins. Spend part of your savings on a 4 GB memory upgrade ($80-100), and buy a larger hard drive only if you need it.

We can't recommend the 2007 20" 2.4 GHz iMac at these prices.

At the bottom, last year's 2.0 Ghz iMac is being blown out at $1,049 (after rebate). It sounds like a nice price, until you realize that you can buy the brand new 2.4 GHz Penryn iMac for just $95 more. With about a 30% difference in raw processing power, the 2.4 GHz Penry is the hands down winner.

Refurbished iMacs

Apple currently lists the following refurbished iMacs at the online Apple Store:

• 20" 2.0 GHz Aluminum, 1 GB/250/SD, $949
• 20" 2.16 GHz Core 2, 1 GB/250/SD, $949
• 20" 2.4 GHz Aluminum, 1 GB/320/SD, $1,099
• 24" 2.16 GHz Core 2, 1 GB/250/SD, $1,199
• 24" 2.4 GHz Aluminum, 1 GB/320/SD, $1,399
• 24" 2.8 GHz Aluminum, 2 GB/500/SD, $1,599

Frankly, we're attracted by the 2006 iMacs with their 2.16 GHz Core 2 Duo CPUs. The 20" model sells for the same price as the newer 2.0 GHz aluminum iMac, and it has a true 24-bit display and doesn't have a glossy screen (which we consider an advantage). At $949, if you want a 20" iMac at a bargain price, it's a hot buy.

We can't get excited about saving $45 vs. after rebate pricing on the 20" 2.4 GHz iMac. It's not quite as overpriced compared with the new 2.4 GHz Penryn iMac, but the Penryn is the value champion.

At the 24" size, the 2.16 GHz 2006 model at $1,199 is attractive. Unlike the aluminum iMacs, it doesn't have a glossy display, and that's what we prefer. With 90% of the processing power of last year's 2.4 GHz iMac and a 14% lower price, we think it's a steal.

If you need more power, the 2.8 GHz iMac offers 16% more power at 14% more money than the 2.4 GHz model, making it almost as good an overall value as the 2.16 GHz Core 2 iMac. But if you're going to spend $1,599 for last year's 2.8 GHz iMac, you may as well come up with the additional $95 (after rebate) for the 2.8 GHz Penryn iMac.

Overall

To sum up, the value champions are the refurbished 2.16 GHz iMacs, while they last, and the 20" 2.4 GHz and 24" 2.8 GHz Penryn iMacs. The 3.06 GHz and Nvidia options on the 24" model are good values, but we don't think most users will need both, so they are better values as build-to-order options on the 2.8 GHz iMac than buying the preconfigured 3.06 GHz mode with Nvidia graphics.

We don't consider the 2.66 GHz Penryn iMac a good value, and we don't see prices on refurbished 2007 iMacs as compelling reasons to choose them over the new models or the remaining refurbished 2006 iMacs.