Core 2 Duos numbered E6xx0 have Conroe cores. Conroe Core 2 Duos numbered E6x00 have a 1066mhz FSB and either 2MB L2 cache (E6300 or E6400) or 4MB L2 cache (all others). Core 2 Duos numbered E6x20 are identical to their E6x00 counterparts, but they have 4MB L2 cache. Core 2 Duos numbered E6x50 have a 1333mhz FSB and 4MB L2 cache. The E6540, the only Core 2 Duo to end in E6x40, is identical to the E6550, but doesn't have Intel Trusted Execution Technology and vPro support. All Conroe Core 2 Duos are fabricated on a 65nm manufacturing process.
Core 2 Duos numbered E4x00 have Allendale cores. All Allendale Core 2 Duos have 2MB L2 cache and a 800mhz FSB. Allendales with half of their L2 cache disabled are sold under the Pentium Dual-Core brand name. Allendales with 3/4 of their L2 cache disabled are sold under the Celeron brand name. All Allendales, be they Core 2 Duo, Pentium Dual-Core, or Celeron, are fabricated on a 65nm manufacturing process.
Core 2 Duos numbered E7x00 or E8x00 have Wolfdale cores. The Wolfdale core is the successor of the Conroe core. Wolfdale Core 2 Duos numbered E7x00 have 3MB L2 cache and a 1066mhz FSB. Wolfdale Core 2 Duos numbered E8x00 have 6MB L2 cache and a 1333mhz FSB. All Wolfdales are fabricated on a 45nm manufacturing process, allowing them to consume less power and emit less heat than Conroes. Additionally, Wolfdale contains the SSE4.1 instruction set, which is useful to multimedia applications.
If you are looking for a cheap Core 2 Duo, I'd recommend the E7200.
EDIT: One 1GB module of RAM will use less power than two 512MB modules of RAM. It will also give you more room to upgrade down the road. With DDR2 prices so cheap, there's really no reason you shouldn't get the one 1GB module.
Edited by stettybet0, 11 August 2008 - 01:28 PM.