Poll: What's the best bang for my photo PC buck?

I'm going to buy a new desktop computer to feed my digital photography appetites, and it's time to let the wisdom of the crowds steer me in the right direction.

There are innumerable options, but there's one particular choice I'm wrestling with: is my money better spent on a PC with a dual-core processor or a quad-core chip with a lower clock frequency?

For the benefit of anybody else in my situation, I thought I'd seek expert guidance from Adobe Systems, Microsoft, Advanced Micro Devices, and Intel and publish the results, but I got conflicting answers. So I'm hoping all you readers can be the tie-breaker on what my priority should be. Feel free to vote and to share any thoughts about that issue or other performance tradeoffs in the Talkback section below.

If I were swimming in money, I could have it both ways with a computer using an Intel Extreme processor, but that's not in the cards. If I were that flush, I'd rather sink the extra money into a lens with roughly five times the usable lifespan of a PC.

To put things in perspective, multicore chips have two more processing engines on each slice of silicon. That theoretically can permit more operations in a given amount of time, but it's more complicated in practice.

With four cores, processors are hotter and therefore have to be run at slower frequencies to keep from overheating. And perhaps biggest on the list, a lot of PC software simply hasn't solved the technical challenges of splitting a single job up into multiple independent threads.

The clock speed/multicore tradeoff is illustrated in prices from Intel's newly announced Penryn generation of Core 2 chips. The dual-core E8500 with 6MB of cache runs at 3.16GHz, and the quad-core Q9300 with 6MB of cache runs at 2.5GHz, and they both have the same price of $266. One thing they have in common is a reasonably fast 1333MHz front-side bus (the pathway between the processor and main memory), but on the quad-core model that bus serves four cores instead of just two.

To set the stage, here are the computing bottlenecks that I notice most dragging down digital photography work I do with Adobe Photoshop and Lightroom: rendering and editing raw photos; converting raw photos to DNG; applying sharpening and noise-reduction filters; metadata-based searches through my 11,000-image catalog; and stitching photos into panoramas.

I recognize there are other price/performance tradeoffs, too--for example more memory or a faster hard drive for better performance when the computer does have to use the drive. But those are relatively easy to change and upgrade later.

Expert opinions
When I asked various companies what they advised, answers differed. Let's compare and contrast:

• Intel spokesman Nick Knupffer: "For digital photography, you are going to be using packages such as Adobe Photoshop that relish the extra threads that a quad-core processor brings to the table. Memory speed or bandwidth is not as crucial."

• AMD spokesman Brett Jacobs: "Given the excellent value of our quad-core Phenom and the improved performance you will see from four cores vs. two using multithreaded applications, the quad-core will offer more bang for the buck compared to a higher-clocked dual-core."

• Tim Grey, author and digital photography technology evangelist at Microsoft's Rich Media Group: "Higher processor clock and front-side bus speed on a dual-core system provides better performance than quad-core. When you consider the premium you pay for quad-core it makes the most sense to invest in the top-of-the-line dual-core. You get better performance at a lower cost."

• Adobe, paraphrased: It depends.

OK, that doesn't do justice to Adobe, which supplied fairly more nuanced information. Some Photoshop tasks can deal well with multicore processors, but others are starved for data from main memory.

"Bandwidth is a big deal," said Adobe's Kevin Connor, who manages professional digital imaging products including Lightroom, Photoshop, and the Digital Negative (DNG) format. According to one illuminating Adobe blog posting, one common Photoshop task that relies heavily on memory bandwidth is the seemingly simple Gaussian blur filter, and one common chore that can't be parallelized is the healing brush.

Things are somewhat different with Lightroom. One of its biggest chores is "de-mosaicking," which converts the "Bayer" checkerboard pattern of red, green, and blue data from a camera's image sensor into an image with red, green, and blue data for each pixel. That process can take advantage of as many as eight cores--the number available in high-end machines such as Apple's Mac Pro or those built on Intel's "Skulltrail" platform, said Tom Hogarty, Lightroom's product manager. DNG conversion, too, can use eight cores, he said.

Another advantage for Lightroom is that it can perform some tasks in the background, a natural fit for multicore. (Thank heavens: With my 3-year-old PC, I often queue up a few batches of Lightroom operations and come back later when they're done.)

Benchmark time
But wait! Let's look at some benchmarks. There are some handy ones here on CNET's review of Apple's iMac. The CNET Photoshop benchmark is a reasonable reflection of my digital photography work, but compare the scores of an iMac with a dual-core iMac with 2.8GHz Intel processors to a Mac Pro with two dual-core Intel 2.66GHz processors (a version tested before the quad-core models were out).

Mac Pro's time to complete the test: 120 seconds. iMac, just a smidgen slower at 125 seconds. The big question here is to what extent the raw-image processing in Photoshop correlates with my own raw-image processing done in Lightroom. Even if Lightroom is much better with multicore, the Photoshop tests aren't a great advertisement for paying for four cores.

When I asked CNET computer guru Rich Brown for his advice, he steered me toward the iMac, in part because Photoshop scores higher on Mac OS X than on Windows. (A Velocity Micro system with a 3GHz dual-core Intel processor had a significantly lower score of 157 seconds, for example, and a Hewlett-Packard system with a 2.4GHz Intel quad-core processor was even worse at 178 seconds.)

Although I'm not opposed to switching from my current Windows setup to Mac OS X, I don't think it's likely. For one thing, I'd have to repurchase some software. More significantly, Apple's lineup doesn't match my needs: the Mac Pro is too expensive, the Mac Mini is too anemic, and I dislike the iMac's lack of expandability, 4GB memory limit, and built-in monitor.

Another non-issue is picking the best laptop. Sure, all the cool kids are forsaking their immovable behemoths for svelte machines, but I already have a reasonable laptop when I need mobility, and for my home machine I want the better price-performance ratio and need the expandability.

Benchmarks notwithstanding, I'm leaning toward quad-core right now. First of all, there's the Lightroom abilities. Second, with the newer generation of processors from both Intel and Advanced Micro Devices, there's less of a premium for quad-core. Last, I'm hoping my machine will last into the era when desktop software catches up with multicore processors.

So that's my opinion. What's yours?