First up is the Ryzen 9 3900, this new 12-core chip has 24 threads, a 3.1GHz base clock, and 4.3GHz Boost. With exception of the clockspeeds, the chip is almost identical to the Ryzen 9 3900X. The big difference is that the Ryzen 9 3900 has a TDP of just 65W, whereas the 3900X has a 105W power envelope. The Ryzen 9 3900 is aimed at system integrators so there's no official pricing for this chip.
Next we have the Ryzen 5 3500X, this chip is exclusively for Chinese OEMs. It's a 6-core, twelve-threaded model with a 3.6GHz core, 4.1GHz Boost, and 65W TDP. Most of the specifications are similar to the Ryzen 5 3600, only the Boost of the Ryzen 5 3500X is 100MHz lower than the former.
Source: AnandTech