Yonah is the predecessor to the Core architecture and is predominantly a mobile chip, and is used at the heart of Intel's Viiv technology. Bit-tech has an article about Yonah beating the top of the range desktop AMD chip, the FX60, clock for clock. Here's an excerpt:

Intel's Core Duo chips are certainly a massive step away from the Netburst architecture. Gone are the days of Intel focusing on ramping clock speeds in order to attain the performance required to compete with AMD's still impressive K8 architecture. Aside from a few feature omissions, Yonah could easily be a very good competitor to the Athlon 64 as a desktop processor, but we have to remember that it is only a mobile processor; a very good one at that.

The lack of 64-bit extensions may be a worry for some, as will the poor FPU performance - the latter showed up in our MP3 encoding test. However, if you disregard the poor MP3 encoding performance, the Core Duo T2600 matches up well to AMD's similarly priced Athlon 64 X2 4800+, even with a 233MHz clock speed deficit in 32-bit environments. From what we understand, all versions of Windows Vista will come in 32-bit, along with 64-bit versions for all but the entry level Starter Edition. We won't know whether there are performance gains from running the 64-bit versions of Vista and we will not be able to answer that until the product is released next year.

When Yonah is running at the same clock speed as AMD's Athlon 64 FX-60, we found that it beat it into a corner in just about every situation. The only situation where we didn't find the 2.6GHz Core Duo chip outperforming the FX-60 was in the MP3 encoding test. The most notable performance advantages were in our Xvid encoding test and all of the gaming scenarios.

I am glad that Intel finally seems to be catching up with AMD, which hopefully will only lead to better competition between the two over time.