A reader at the TechPowerUp forums reportedly stumbled on a mysterious AMD Radeon RX 640 graphics card during a routine installation of the AMD Radeon Adrenalin Edition 19.4.3 graphics driver. Additionally, there were also mention of the AMD Radeon 630, Radeon 625 and Radeon 620.
As noted by TechPowerUp, the Radeon RX 640 seemingly shares the same device ID as the existing Radeon RX 550X. Therefore, it's safe to assume that the RX 600-series is just another rebrand. If that's the case, then the Radeon 630 is probably the rebrand for the Radeon 540X as well. We're unsure about the Radeon 625 and Radeon 620 for the moment.
Specs
| Row 0 - Cell 0 | AMD Radeon RX 640 | AMD Radeon RX 550X | AMD Radeon 630 | AMD Radeon 540X |
| Architecture (GPU) | ? | GCN 4.0 (Lexa) | ? | GCN 4.0 (Lexa) |
| Shading | ? | 640 | ? | 512 |
| Texture Units | ? | 40 | ? | 32 |
| Base Clock Rate | ? | 1,100 MHz | ? | 1,124 MHz |
| GPU Boost Rate | ? | 1,287 MHz | ? | 1,219 MHz |
| Memory Capacity | ? | 2GB GDDR5 | ? | 4GB GDDR5 |
| Memory Clock | ? | 6 Gbps | ? | 6 Gbps |
| Memory Bus | ? | 128-bit | ? | 64-bit |
| Memory Bandwidth | ? | 96 GB/s | ? | 48 GB/s |
| ROPs | ? | 16 | ? | 16 |
| L2 Cache | ? | 512KB | ? | 256KB |
| TDP | ? | 50W | ? | 50W |
| Transistor Count | ? | 2.2 billion | ? | 2.2 billion |
| Die Size | ? | 103 mm² | ? | 103 mm² |
Early Navi rumors suggested that AMD would roll with the RX 3000-series branding for its upcoming 7nm graphics cards. One theory is that the chipmaker is aiming to segment its Navi products from its other offerings. It wouldn't be the first time we see this tactic; Nvidia currently separates its Turing stack into the GTX 20-series and GTX 16-series to differentiate the models with the RT and Tensor cores from the ones that don't.
If AMD keeps its Navi product line under the RX 3000-series branding, the chipmaker would be free to market its non-Navi offerings under a different moniker, which in this case would be the RX 600-series for the rebranded models based on the rewarmed Polaris silicon. This could also indicate that AMD is focusing on the performance market and might not offer lower-tier Navi models until a later date.
The current Radeon RX 550X and Radeon 540X are based on AMD's worn-out Graphics Core Next (GCN) 4.0 architecture. Both graphics cards use Lexa silicon, which is the codename for Polaris 12, manufactured by TSMC under the 14nm process node. These 50W parts are popular among OEMs as they prove to be a pretty capable replacement for integrated graphics in entry-level desktops and mobile systems.
It's unknown at this point in time whether the RX 600-series will retain the same silicon and manufacturing process or get an upgrade to the 12nm node. We would expect an increase in the operating clocks at the very least. Either way, it appears that AMD wants to give its GCN architecture one more run before moving on to Navi.
