AMD caves-in to demand for Zen 3 support on X470 and B450 boards with an optional Beta BIOS, here's all you need to know about AMD's proposed upgrade path

After last week's announcement that the upcoming Zen 3 Vermeer Ryzen 4000 desktop CPUs won't be compatible with anything less than an X570 or B550 chipset-based motherboard, AMD has now backtracked and is promising Zen 3 support for owners of X470 and B450 motherboards as well. This development comes in the wake of severe backlash by the community as AMD had hitherto promised Socket AM4 support for all Ryzen processors through 2020. 

AMD has posted the following statement on Reddit pertaining to this development. The full posting can be viewed at the Source link below.

As we head into our upcoming “Zen 3” architecture, there are considerable technical challenges that face a CPU socket as long-lived as AMD Socket AM4. For example, we recently announced that we would not support “Zen 3” on AMD 400 Series motherboards due to serious constraints in SPI ROM capacities in most of the AMD 400 Series motherboards. This is not the first time a technical hurdle has come up with Socket AM4 given the longevity of this socket, but it is the first time our enthusiasts have faced such a hurdle.

Over the past week, we closely reviewed your feedback on that news: we watched every video, read every comment and saw every Tweet. We hear that many of you hoped for a longer upgrade path. We hear your hope that AMD B450 and X470 chipsets would carry you into the “Zen 3” era."

The issue originally stemmed from the fact that most Socket AM4 motherboards had a 16 MB BIOS as certain older AM4 processors could only address the first 16 MB of ROM. Therefore, as new Ryzen processor generations started to emerge, AMD had to cut support for the oldest one possible in order to free up space on the ROM. For example, X570 and B550 motherboards forego support for the Athlon A series, Ryzen 1000, and Ryzen 2000 APUs so as to accommodate AGESA code for Ryzen 2000 CPUs and up. 

Due to this very limit, AMD originally planned X470 and B550 boards to support Ryzen 1000 to Ryzen 3000 chips but not any higher. Even if the board had a 32 MB ROM, it would have to be partitioned to allow for the "regular" 16 MB BIOS for current generations and the "opt-in" Beta BIOS for future generations, which can complicate firmware updates and make the whole thing look cumbersome. 

AMD gave out several pointers on the proposed upgrade path. Let's have a look at them in detail.

We will develop and enable our motherboard partners with the code to support “Zen 3”-based processors in select beta BIOSes for AMD B450 and X470 motherboards."

What this means is that AMD will supply new AGESA code to motherboard OEMs to allow upgrade to Zen 3. These will be "forked" BIOSs always labeled as "Beta", and it is totally upon the OEM whether to issue them to end-users or not.

These optional BIOS updates will disable support for many existing AMD Ryzen™ Desktop Processor models to make the necessary ROM space available.

The select beta BIOSes will enable a one-way upgrade path for AMD Ryzen Processors with “Zen 3,” coming later this year. Flashing back to an older BIOS version will not be supported."

Users who wish to flash the "Beta" BIOS will have to forego compatibility with older Ryzen processors. AMD has not yet clarified which generations would be removed, but we expect Ryzen 1000 and either Ryzen 2000 APUs or CPUs (or both) to be ripped out to make space for Ryzen 4000. Once a user flashes this "Beta" BIOS, there is no turning back. 

To reduce the potential for confusion, our intent is to offer BIOS download only to verified customers of 400 Series motherboards who have purchased a new desktop processor with “Zen 3” inside. This will help us ensure that customers have a bootable processor on-hand after the BIOS flash, minimizing the risk a user could get caught in a no-boot situation.

Timing and availability of the BIOS updates will vary and may not immediately coincide with the availability of the first “Zen 3”-based processors."

It looks like AMD may implement some sort of mechanism to ensure that only verified 400-series board owners who have bought a Zen 3 processor will get access to the "Beta" BIOS. AMD would want to avoid a situation wherein the user would flash the new "Beta" BIOS beforehand only to render the current CPU non-bootable.

AMD currently has a Short Term Processor Loan Boot Kit program to allow for a compatible BIOS upgrade on older boards before drop-in support is enabled for the new processor. Anandtech checked with AMD if this scheme still holds true for Zen 3 to which the company replied that there's a possibility, but things haven't been worked out yet. More importantly, there is no guarantee that these "Beta" BIOSs would be available on day 1 of the Zen 3 launch.

This is the final pathway AMD can enable for 400 Series motherboards to add new CPU support. CPU releases beyond “Zen 3” will require a newer motherboard.

AMD continues to recommend that customers choose an AMD 500 Series motherboard for the best performance and features with our new CPUs."

AMD is now confirming that the upgrade path for 400-series boards will end with Zen 3. Anything beyond will require a 500-series at the minimum. Truth be told, even current 500-series owners may be required to upgrade when Zen 4 Ryzen 5000 releases sometime in 2021. By then, we may see DDR5 and PCIe Gen5 making their debut, which would necessitate a new socket in all likelihood just like how Threadripper had to move to a new sTRX4 socket and the TRX40 chipset to accommodate Threadripper 3000's increased PCIe Gen4 lane count.