AMD X870E, X870, B850, and B840 Chipsets

Along with the Ryzen 9000 Granite Ridge series, AMD is debuting their 800 series desktop motherboard chipset family. The processors are placed in the existing Socket AM5, and as such are compatible with any AMD 600-series chipset motherboard with a BIOS update. Helping things along is the fact that nearly every AM5 motherboard comes with USB BIOS Flashback, which should let you blind-flash your BIOS even if you have an "incompatible" processor.

AMD hasn't changed the I/O of its processors, as we detailed on the previous page, but identified the reasons why some of its 600-series chipset models were vastly outselling the others. Market studies showed that enthusiasts are drawn to the top X670E, and the rest of the crowd to the well-rounded B650, with no takers for the X670 and B650E. AMD set out to correct these by shuffling up the feature-sets among its 800-series chipset models, while also using the occasion to standardize a few I/O features, such as USB4, and encouraging its motherboard partners to provide new connectivity options, such as Wi-Fi 7.


The AMD X870E chipset leads the pack in terms of connectivity. It is a dual-chip solution, much like X670E and X670. You are assured PCI-Express Gen 5 for the x16 PEG slot, as well as the CPU-attached NVMe slots; while the chipset puts out up to 16 Gen 4 PCIe lanes. Also, motherboard designers are mandated to provide 40 Gbps USB4 connectivity.

The X870 (non-E) is a lite version of this chipset, and is a single-chip solution, much like the B650E. You'll still get PCI-Express Gen 5 x16 for the PEG slot, as well as Gen 5 for the CPU-attached NVMe slots, however the chipset only puts out 8 Gen 4 PCIe lanes for general purpose I/O. Much like X870E, with X870 you are assured of USB4 connectivity.

The B850 is a successor of the B650. It is a single-chip solution just like X870, but here, motherboard vendors are allowed to wire out the PCI-Express x16 PEG slot as Gen 4. The CPU-attached NVMe interfaces, however, should remain Gen 5 capable. Motherboard vendors can still provide Gen 5 x16 PEG if they want to, but it's optional. USB4 isn't mandatory, so a vendor can design an X870 motherboard and simply pull out the USB4 interface to label the board as B850. Like X870E and X870, the B850 chipset supports both CPU and memory overclocking.

Lastly, there's the B840, an entry-level chipset meant to succeed the A620 and A620A. The PCI-Express x16 PEG runs at a primitive Gen 3 speed. The chipset puts out just 8 Gen 3 lanes. There's no CPU overclocking support, only memory. The B840 should hence power the vast majority of entry-level or commercial desktop motherboards.

Overclocking

Curve Shaper is a new feature being introduced with Ryzen 9000 series processors. It's part of the AMD CBS, which means it can be configured in the UEFI setup program, should the motherboard vendor choose to have a GUI there, or using Ryzen Master on Windows. Curve Optimizer enabled PBO and PMF-aware under-volting, while Curve Shaper lets end-users reshape the underlying voltage curves to fine tune voltage control across different workloads and frequencies.


A side effect of giving processor models such as the 9900X (120 W), 9700X (65 W), and 9600X lower TDP than their predecessors, the 7900X (170 W), and 7700X (105 W), is that Precision Boost Overdrive (PBO) now scoops out more performance, as it raises the package power for the processors. AMD claims further performance gains of 6% for the 9900X, and up to 15% for the 9700X (which goes to show that 65 W is quite conservative for this SKU).


Native DDR5 support has been increased to DDR5-5600, and support has been added for overclocked memory as fast as DDR5-8000. To achieve this, a 1:2 clock divider is engaged between FCLK and MCLK as soon as memory clock is set higher than DDR5-6000. You may manually force a 1:1 divider "and with some luck" you will be able to run DDR5-6400—essentially the same as with Zen 4. DDR5-8000 support has been released by AMD through an update to the AGESA microcode, for motherboard vendors to integrate with even their older AMD 600-series chipset products. There should be a new wave of enthusiast PC memory with AMD EXPO profiles for DDR5-8000 and everything under (such as DDR5-7200, DDR5-6800, etc.). In terms of performance it is interesting to see if DDR5-8000 1:2 can beat DDR5-6000 1:1 in a wide range of scenarios, which could make it a worthwhile investment. TPU has tested Zen 5 memory scaling in a separate article.

Socket AM5

Here are a few pictures of Socket AM5, the star-attraction with this platform. This is a land-grid array (LGA) socket with 1,718 pins.


As with every LGA socket, the pins are on the motherboard, whereas the processor package has contacts that interface with those pins, while a retention brace holds the package in place with a locking lever. Installing a processor on AM5 is similar to doing so on any of the dozens of Intel LGA sockets.


On Socket AM4, removing the four mounting screws resulted in the backplate falling off, which meant you needed three hands when installing a cooler, and several vendors also bundled their own backplates. On Socket AM5 the backplate isn't designed to be removed, which makes cooler installation MUCH easier.


The caps for the socket are not identical to the Intel LGA sockets, so you can't reuse them.