Samsung is already working on the successor to the popular Galaxy S3 smartphone. Sources claim the South Korean tech giant recently produced a test version of a 28nm High-K Metal Gate (HKMG) processor codenamed Adonis that will ultimately find a home in their next generation flagship handset.

The quad-core chip, which will likely be called an Exynos 5400, uses ARM’s Cortex A15 architecture and will ship with a beefy GPU that reportedly requires a low amount of power. Samsung’s current Exynos 5250 also uses the Cortex A15 architecture but is built on the larger and less efficient 32nm process.

HKMG allows for low power-consuming chips due to the fact that ultra-miniaturization is possible without current leakage. This is a key problem generally associated with shrinking processes on the traditional SiON silicon based process.

It is believed that the Exynos 5400 will enter mass production either by the end of this year or in early 2013. If Samsung stays on schedule, it should be the first mobile applications processor (AP) on the market to utilize the 28nm HKMG manufacturing process. Depending on which report you follow, we could see the Galaxy S4 hit retail sometime next April or May.

For what it’s worth, market research firm Strategy Analytics said Samsung ranked second in the mobile AP market with a market share of 25.9 percent during the second quarter of 2012. Qualcomm led all others with a 38.8 percent share. It’ll be interesting to see how these figures shift in the third quarter and beyond once Samsung starts mass producing the Exynos 5400.