The blog OMG Ubuntu reports that a new version of the Raspberry Pi 4 Model B has been (quietly) introduced. "The key difference? It now uses a dual-RAM configuration." The Raspberry Pi 4 Model B (PCB 13a) adopts a dual-RAM configuration to 'improve supply chain flexibility' and manufacturing efficiency, per a company product change notice document. Earlier versions of the Raspberry Pi 4 use a single RAM chip on the top of the board. The new revision adds a second LPDDR4 chip to the underside, with a couple of passive components also moved over... In moving to a dual-chip layout, Raspberry Pi can combine two smaller — and marginally cheaper — modules to hit the same RAM totals amidst fluctuating component costs...

This change will not impact performance (for better or worse). The Broadcom BCM2711 SoC has a 32-bit wide memory interface so the bandwidth stays identical; this is not doubling the memory bus, it's just a physical split, not a logical one. Plus, the new board is fully compatible with existing official accessories, HATs and add-ons. All operating systems that support the Pi 4 will work, but as the memory setup is different a new version of the boot-loader will need to be flashed first.