Allendale
For a very long time, it was considered that the low-end Core 2 Duo desktop processors (E6300, at 1.86 GHz and E6400, at 2.13 GHz, both with 2MiB L2 cache) were specimens of the Allendale core. This wasn't true when the Core 2 Duo was released mind you. In actuality, these models were Conroe (4 MiB L2 cache) cores with half their L2 cache disabled. The Allendale core is manufactured with 2MiB L2 cache in total. The situation has changed however when the Allendale core was released with the Core 2 Duo E4300 in January 21st 2007, which can now be identified with it's L2 Stepping, there are now 2MiB cache total Allendale based Core 2 Duo E6300 and E6400 processors in addition to the original Conroe based E6300 and E6400 that were release back in July 26th, 2006.
Basically, the only difference between the Allendale and Conroe cores is that Allendale only physically has 2MiB of LV2 cache on it's core vs Conroe which has 4MiB cache on it's core.
Quoted from The Tech Report: