Small businesses, pay attention: Now that the first six-core desktops are out, we wanted to see how the massive Excel spreadsheets we often use for testing purposes would perform, specifically on whether adding more cores would increase performance.

Now that the first six-core desktops are out , I wanted to see how the big spreadsheets I often use for tests would perform. I tested on the first couple of Gulftown systems that PCMag received and ended up with good results, but I didn't always see the performance improvements I expected. My results point out the strengths and limitations of multicore computing when it comes to heavy-duty applications.

Both machines I tested used the Intel Core i7-980 Extreme Edition, which has six cores and 12 threads. The core's official speed is 3.33 GHz, but the Extreme Edition designation means it was designed to be overclocked--and both vendors did just that. The machines had different speeds of memory, which also should impact performance.



One was the Falcon Northwest Mach V, which had a 4.18-MHz version of the processor and 12GB of 1,333-MHz DDR3 memory. The other was a Maingear Shift, with the processor at 4.3 GHz and 6GB of 2,000-MHz DDR3 memory. Both had SSDs as boot disks as well as hard drives, though I don't believe that has any impact on performance, and the spreadsheets are loaded in memory. They also had ATI Radeon HD 5970 graphics, though again that's irrelevant to spreadsheets. (I'm not going to try to review the machines here. For PCMag's reviews, click on the links above.)

For comparison, I looked at how these machines did on my basic Excel 2007 spreadsheet tests versus the fastest machine I had previously tested -- an overclocked Falcon Northwest Mach V running a previous generation of the Intel Core i7-965 quad-core chip at 3.99GHz. There's a slight difference in clock speed, but the bigger difference is that the older version was a 45nm quad-core chip; while the new one is a 32nm six-core one.

A Monte Carlo simulation I tried took 3.5 seconds on the quad-core system, compared with 2.5 seconds on the Falcon Northwest six-core system and 2.4 on the Maingear one. (The difference between the two six-core systems is not significant; I'm not that accurate on the stopwatch. As a result, it may be time to get a new test. When I started using this, it took 78 seconds on a Pentium D-based system.) That's a notable improvement in moving from the four-core system to a six-core one. Monte Carlo simulations in Excel really take advantage of a multithreaded system, and this shows up quite clearly.

On a pivot table with 87,000 rows of data, it took 48 seconds on the quad-core system, 35 seconds on the Falcon Northwest, and 34 second on the Maingear. Again, it's a nice improvement.

But my toughest test is a very large data table-driven spreadsheet, which took 56 minutes on the quad-core, 56 minutes on the Falcon Northwest six-core, and 51 minutes on the Maingear six-core. Earlier, I had seen big improvements here based on improved clock speeds, but moving from four cores to six didn't seem to move the needle much (and this in a spreadsheet where the differences are really notable).



As I looked more closely at this spreadsheet while looking at performance under task manager, it became apparent that most of the time it was really only using four threads. In this case, the slight improvement in clock speed and the faster memory did seem to make a difference, but more cores didn't.

In part, this is the problem that we're seeing with lots of desktop applications. Many are sequential, in which case multiple cores or multiple threads don't help. And many applications have yet to be fully designed for multiple cores. Excel 2007, for example, was designed to make use of multiple cores only in certain special situations, such as Monte Carlo simulations; the upcoming Excel 2010 adds more support for multitasking but still not for every function . (I'll write a bit more about this in a later post.)

The bottom line is that for some things, the additional cores make a big difference; for others they don't. And that's just in one application.