Phoronix published a review on the Performance-Per-Watt & How The Raspberry Pi 2 + Pi Zero Compare To Old NetBurst CPUs

A quote from the article:

After starting to run some Raspberry Pi Zero benchmarks this weekend, I'm back today with more benchmarks. In this article is also an interesting comparison showing the performance of the Raspberry Pi Zero and Raspberry Pi 2 against old "Northwood" Pentium 4 and Celeron processors from the Socket 478 NetBurst days. The many results in this article also include power consumption and performance-per-Watt metrics for this $5 ARM single board computer.

There are results from a few different comparisons in this article. One of the main things was seeing if the Raspberry Pi can compete old Intel x86 CPUs from more than one decade ago. For this comparison I used the Phoronix Test Suite data from the birthday article earlier this year of Comparing Today's Modern CPUs To Intel's Socket 478 Celeron & Pentium 4.

 Performance-Per-Watt & How The Raspberry Pi 2 + Pi Zero Compare To Old NetBurst CPUs @ Phoronix