While AMD is continuing support for the AM4 platform with its 3rd Gen Ryzen processors, backwards compatibility may not extend to all 300-series motherboards. Reports emerging from AMD’s post-announcement press gathering suggest BIOS chip limitations could be the determining factor in whether your board can support 3000-series Ryzen processors or not.

AMD’s AM4 platform is set to stick around around until next year, 2020. Until that day arrives, AMD has promised that all of its desktop Ryzen chips will be physically compatible with the current PGA AM4 socket and accompanying chipsets. For the most part, forgetting Threadripper for a moment, AMD has stuck to its word, too. Although support for 3000-series chips may now come down to a question of 16MiBytes.

The BIOS chips on AM4 motherboards are only smol, and this could constrain the amount of CPU microcode vendors are able to store all at once. While 400-series motherboards are able to store a roomy 32MiBytes, enough for all three generations of Ryzen’s code, the older 300-series boards are stuck at 16MiBytes.