AMD says that their upcoming AGESA 18.104.22.168 firmware for the AMD Ryzen will enhance memory overclocking and compability, and will bring virtualization-related features.
AGESA is an acronym that stands for "AMD Generic Encapsulated System Architecture." The AGESA is responsible for initializing AMD x86-64 processors during boot time, acting as something of a "nucleus" for the BIOS for your motherboard. Motherboard vendors take the core capabilities of our AGESA updates and build on them with their own "secret sauce" to create the BIOS files you download and flash. Today, the BIOS files for AMD AM4 motherboards are largely based on AGESA version 22.214.171.124.
AMD has began beta testing a new AGESA (v126.96.36.199) that is largely focused on aiding the stability of overclocked DRAM (>DDR4-2667). Testing has begun transitioning into release candidate and/or production BIOSes for you to download. Depending on the QA/testing practices of your motherboard vendor, full BIOSes based on this code could be available for your AM4 motherboard starting in mid to late June. Some customers may already be in luck, however, as there are motherboards-like the Gigabyte GA-AX370-Gaming5 and ASUS Crosshair VI-that already have public betas.
If you're the kind of user that just needs virtualization, then AGESA 188.8.131.52-based firmware will bring fresh support for PCI Express Access Control Services (ACS). ACS primarily enables support for manual assignment of PCIe graphics cards within logical containers called "IOMMU groups." The hardware resources of an IOMMU group can then be dedicated to a virtual machine.
This capability is useful for users that want 3D-accelerated graphics inside a virtual machine. With ACS support, it is possible to split a 2-GPU system such that a host Linux OS and a Windows VM both have a dedicated graphics cards. The virtual machine can access all the capabilities of the dedicated GPU, and run games inside the virtual machine at near-native performance.
Most importantly, AGESA 184.108.40.206 officially adds 26 new parameters that can improve the compatibility and reliability of DRAM, especially for memory that does not follow the industry-standard JEDEC specifications (e.g. faster than 2667, manual overclocking, or XMP2 profiles).
The AM4 platform has so far been effectively limited to memory speeds of DDR4-3200. Not only that, but the supported range of options from DDR4-1866 to DDR4-3200 was in large 266MT/s increments. With AGESA 220.127.116.11, memory frequencies have not only been expanded all the way up to DDR4-4000, but between DDR4-2667 and DDR4-4000 the increments have been reduced to 133MT/s. This mean that more memory kits will be able to be run at their rated speed and also reduces the high-speed memory gap that the AM4 platform had with Intel's mainstream LGA1151 platform.
The update also unlocks new memory timings. Up until now, only five primary memory timings have been adjustable and there wasn't even a command rate option, which was natively locked to the most aggressive 1T setting. All of this should help improve overclocking and compatibility with DDR4 memory kits that have been engineered with Intel platforms in mind.