Launch Dates of AMD 8 Series Chipsets

[Mats]

why does AMD always release the integrated graphics(lower end) ones first?like when they released 790GX and then the 790FX Enthusiast boards later?

Wrong.
790FX came nine months before GX, on the same day the first Phenom 65 nm (translation lookaside buffer flaw enabled stepping B2) was released back in 2007.
It's even made in 65 nm, while GX is 55 nm.

The 790FX, 790X and 770 chipsets were launched on November 19, 2007

The 780G chipset was released worldwide on March 5, 2008 during CeBIT 2008 [8],

The 790GX chipset was released on August 6, 2008.

The 785G was announced on August 4, 2009.

http://en.wikipedia.org/wiki/AMD_700_chipset_series