Intel Core 2 Duo E6300
An early engineering sample of the Core 2 Duo 'Conroe'. The first batches are called 'A0-silicon' or 'A0-stepping'. This particular CPU is A1-stepping and dates back to the last week of 2005; about a half year before it's official launch in July 27, 2006.
Back in 2005 Intel still had their Pentium 4 and Pentium D as flagship processors. The Pentium D was able to keep up with the Athlon64 X2 but the Athlon was often favourable. Many people speculated about the new 'Conroe' processor and as more information became known, people got exciting about it's performance.
It took a while before benchmarks popped up. Just a few engineering samples were floating around and when one popped up on auction sites it was being sold for a decent price. Besides the low quantity of leaked engineering samples the then new 'Conroe' processor needed a specific motherboard equipped with VRM11. Normal Pentium 4 and Pentium D have the same socket but are equipped with VRM10.1 and often BIOS-support and/or chipset support was absent. Back in '06 I wrote How-to: Compatibility of socket 775 for Intel systems for those who wondered if they can run a Core 2 Duo on their motherboard.
Just a few months before it's official release some benchmarks and screenshots popped up showing that the first samples could outperform high-end AthlonX2's and Pentium D's with ease. At it's release many people opted for the Core 2 Duo and those first CPU's already ran beyond 3GHz. In 2006 I had this E6400 running at 3.2 GHz using air-cooling. It ran happy for years until it was replaced by a faster system.