AMD Launches Ryzen 9 5900 & Ryzen 7 5800 OEM Processors | TechPowerUp
 
AMD has quietly launched two new Zen 3 processors for the OEM market with the Ryzen 9 5900 and Ryzen 7 5800. The Ryzen 9 5900 is a 12 core 24 thread processor with a base clock of 3.0 GHz and a max boost clock of 4.7 GHz along with a TDP of 65 W. The clock speeds were lowered due to the 65 W TDP with a base clock is 700 MHz lower than the 5900X while the boost clock is only 100 MHz slower. The Ryzen 7 5800 is an 8 core 16 thread processor with a base clock of 3.4 GHz and a boost clock of 4.6 GHz along with a TDP of 65 W. The base clock is reduced by 400 MHz and the boost clock by 100 MHz compared to the 105 W TDP 5800X. The Ryzen 9 5900 is only ~5% slower than the Ryzen 9 5900X despite a 61.5% lower TDP and reduced clock speeds according to UserBenchmark results. These new processors are now shipping in systems from various integrators such as the Alienware Aurora Ryzen Edition.
 
I will make an educated guess that CPU supplies are slightly better which is why these CPUs are available for OEMs.