
UEFI takes up a lot more space than the old text-based BIOS and it appears motherboard makers are running out of space on Socket AM4 motherboards. Due to the fact that Bristol Ridge APUs weren't widely distributed, and they're nearly up to two years old, an easy solution for motherboard makers seems to drop support. The reason why it's not possible to keep Bristol Ridge support isn't known, it could be because the base code of the platform or the microcode per CPU is too large, but there are no specifics.
The simple solution would be to use 256Mb BIOS chips, but AnandTech reports motherboard makers aren't keen to do this because of inventory, purchase agreements, and the higher cost.
The simple way to support all the processors is to increase the size of the BIOS chip, by moving from 128 Mb to 256 Mb. At least two vendors told us that the price of these larger chips is more than double the 128 Mb chips. Not only this, but they have so many 128 Mb chips in stock already (or purchase agreements), it would not be economically feasible to switch and dump. One company, Biostar, said that they were implementing motherboards with two BIOS chips in a striped configuration, giving an effective capacity of 256 Mb, in order to solve this issue. The only downside here is that the system is using two BIOS chips, effectively doubling the cost to implement a BIOS on the motherboard. For low end systems, this is an additional cost that might push the product out of a competitive price range.Another infeasible solution is to bifurcate BIOS releases, but that results in the risk of a customer flashing the wrong BIOS version. Or perhaps motherboard makers could drop useless stuff from their BIOS...