ASRock has developed a special expansion card that connects to the PCIe word and allows you to turn an AMD B650 chipset motherboard into a motherboard based on a more advanced AMD X670 chipset. The Level1Techs YouTube channel spoke of an unusual novelty.
As you know, AMD X670 chipset consists of two Promontory 21 chips, while AMD B650 chipset consists of only one such chip. So add a second chip promontory 21albeit on an expansion card, allows you to convert a board based on the B650 chipset into a board based on the X670 chipset.
ASRock X670 XPANSION KIT custom expansion board is a concept device. It requires a special B650 LiveMixer motherboard (not the one already commercially available) and special BIOS firmware.
The expansion card includes the AMD B650 chipset itself, two M.2 slots for PCIe 4.0 x4 NVMe drives, three USB Type-A ports, one USB Type-C (10Gb/s), two SATA-III ports and a 10 Gigabit network port. In comparison, the regular motherboard version of the ASRock B650 LiveMixer board comes with a 2.5Gbps network adapter.
It is important to note that the X670 XPANSION KIT expansion card not only requires a free PCIe slot, but also a special mainboard with an external controller and J2 connector for connection. These devices have not yet gone on sale and it is not known if they will.
Should ASRock nevertheless decide to release this device for sale, then it could be interesting for enthusiasts. On the other hand, it is very likely that the cost of such an expansion card will be higher than the price difference between motherboards based on AMD B650 and X670 chipsets.