The Guru of 3D published a review on the Radeon RX 6400
A quote from the article:
Meet AMD's Radeon RX 6400. It has 4GB of 64-bit RAM and a whiff of Inifinity Cache (16MB L3). This card might operate at Radeon RX 480 levels when connected to a PCIe Gen x4 connection (3.0/4.0).Radeon RX 6400 Review