First gen Threadripper includes the following:
- 1900X (8 cores)
- 1920X (12 cores)
- 1950X (16 cores)
Second gen:
- 2920X (12 cores)
- 2950X (16 cores)
- 2970WX (24 cores)
- 2990WX (32 cores)
Third gen:
- 3960X (24 cores)
- 3970X (32 cores)
- 3990X (64 cores)
- 3945WX (12 cores)
- 3955WX (16 cores)
- 3975WX (32 cores)
- 3995WX (64 cores)
All Threadripper chips are on 4094-pin LGA sockets. The first two generations use the X399 chipset. The third generation uses the TRX40 chipset for the X parts, which are available on motherboards you can purchase, and the WRX80 chipset for the WX parts, which are OEM only (basically just Lenovo at this point, last I checked).
There are no Zen 3 Threadripper chips yet announced. One can only hope they will expand the non-OEM versions back to lower core counts, because starting at 24 cores with Zen 2 was an incredibly stupid decision.
The 5950X is a consumer-level chip running on AM4, which has extremely limited PCIe lanes and just two memory channels.
Getting a third-gen Threadripper chips looks to be not particular easy right now, with stock low and prices high. Unless, perhaps, you go with an OEM solution via Lenovo.