It entirely depends on what sort of chips you're talking about. Architecture matters a lot more than pure Ghz in most cases.

It also depends on what you are doing with it. If the code doesn't take advantage of multi-core systems then one will run it and the other will just idle along. What are you going to do with it?

The thing is I have a Intel Pentium D 830 right now. I am looking at a Intel E6300 1.8 GHZ Cour 2 Duo. I found a web site that benchmarks the E6300 against mainly an AMD processor but also includes a Pentium D 900 series. The E6300 looks favorable. The test was done in August 2006 so it is dated quite a bit, in terms of tech. The link is.

WWW Link

You already have a dual core CPU, so that makes it easier. E6300 is better than your 830. Even some single core P4 are better than the 830. Doesn't mean you have to upgrade though. Just decide if it's worth the money.

The high end AMD FX parts outperform the low end Core 2 Duo parts, but they cost $1000. The fastest AMD X2 parts like 5600+ (2.8 Ghz) match up with a E6300 (1.8 Ghz) but it costs more. AMD is trying to price competitively, so for the same price as a E6300 you get a X2 4600+ which is almost as good. The other benefit for C2D is the easy OC.

Here's another link that compares performance and price:

http://www.tgdaily.com/2007/03/05/price_performance_analysis_03_04_2007/

AMD's current product line though is old and reaching it's potential while Core 2 Duo has lots of room to increase clock rates. I don't know if AMD new design later this year (Q3?) will work on a current AM2 board (I doubt it). For future upgrade you're better off buying now a LGA775 board and a low end C2D, over buying a AM2 board and a X2.

I'm looking to upgrade from my ancient Athlon XP. I've always preferred AMD, but I don't think I can wait though for AMD's new line.

You have to make sure you're comparing the same thing. As long as the dual core and single core CPU you're comparing are of the same architecture, then the dual 1.8 GHz won't give you single 3.6 GHz performance. But a better designed and more efficient dual core may blow away an older architecture single core of twice the clock rate.

An example is that (dual core Netburst) Pentium D 3.6 GHz and (single core Netburst) Pentium 4 3.8 GHz have the same performance in some applications, so dual core wasn't worth it. But the new architecture Core 2 Duo 1.8 GHz is on par performance wise to both of those older processors.

BTW: AMD is supporting AM2 long term so their new "K8L" line should work on current AM2 boards after a BIOS update. So AM2 has long term upgrade potential.

Tom's Hardware is a great site. You can also find some good articles there, which help you to understand exactly what some of the more arcane specs mean for each of the various components.

It's a lot less user-friendly than PCWorld, but equally practical, and usually more timely (PCWorld does a "state of the industry" on various subcomponents about once every ~9 months, Tom's seems to do it a couple times a year).

Regardless of whether the second core is used or not, Intel's Core processors are architecturally superior to Netburst (used in Pentium 4). For this reason, even in single-core apps, a low-end Core 2 Duo will beat all but the fastest Pentium EE processors.