Let’s start with the conclusion.

Final conclusion: The Atom is handling better multiple tasks, it manages to distribute its tasks to all of its cores. It can handle multiple requests simultaneously and this makes it more functional. While the P4 is faster per clock speed, it can work only on one task at a time, where the processor dedicates all of its resources. When a new task arrives it simply discards it or delays it, while the ATOM can process multiple requests at once the P4 cannot. When the load was higher the ATOM outperformed the Pentium 4 almost 100% of the time. The MySQL performance difference was also very clear in that the ATOM outperformed the Pentium 4 several times over.

This quote comes from this word doc from this page. http://www.singlehop.com/servers/atom_tests.php

Test Name
P4 2.8 Ghz
Dual-Core ATOM 330
Results

MySQL 1,000 Select Queries from 10 Clients
5,948
15,661
¹ATOM is 263% Faster

MySQL 1,000 Select Queries from 100 Clients
5,721
15,203
ATOM is 265% Faster

MySQL 1,000 Update Queries from 10 Clients
1974
2603
ATOM is 31% Faster

MySQL 1,000 Update Queries from 100 Clients
2016
2389
ATOM is 19% Faster

MySQL Stress Test
2000
2332
ATOM is 17% Faster

Disk Read/Write - Write 5 GB File to Disk
2:41 Minutes
2:13 Minutes
ATOM is 13% Faster

who is SingleHop? A hosting company that offers the Intel Atom server as their cheapest hosting solution.