AMD A4-9120C SoC socket: Socket FT4

What the A4-9120C SoC is

The AMD A4-9120C SoC is a 1.6 GHz dual-core soldered mobile processor from January 2019. It runs one Excavator module with 2 cores at 1.6 GHz base and up to 2.4 GHz boost on one core, so 2 cores give 2 threads. Cache is 1 MB of shared L2 with 160 KB of L1 on a 28 nm process with 1.2 billion transistors. Power is rated at 6 W in a Socket FT4 BGA package with DDR4 memory and PCIe Gen 3 lanes.

The C suffix marks the 6 W Chromebook tuning against 10 W and 15 W Stoney parts at higher clocks, which is why the 9120C at 1.6 GHz runs fanless while A4-9120 parts at 2.2 GHz need active cooling. AMD announced the 9120C on January 7, 2019 with the A6-9220C for Chromebooks. The chip supports AVX, AVX2, AES and AMD-V with Radeon R4 graphics with 3 compute cores up to 600 MHz.

Low clocks with a 6 W envelope suit fanless Chromebooks with soldered DDR4 and eMMC storage. The single-channel DDR4-1866 path keeps board cost down. That is why the 9120C shipped in education Chromebooks with all-day battery targets.

Socket and motherboard compatibility

The A4-9120C SoC is soldered to FT4 boards and cannot be replaced. It fits Chromebook boards with FT4 solder lands and a BIOS that lists the A4-9120C. The Socket vs chipset: what decides whether a CPU works guide covers pairing rules.

Fanless Chromebook boards are the natural match. Boards built for the 9120C carry the soldered SoC with a board spreader for the 6 W class. Socketed boards cannot accept the ball package.

Memory, PCIe and cooling

Memory is single-channel DDR4-1866 through the on-chip controller, with up to 8 GB typical on Chromebook boards. The controller runs one 64-bit channel from the die. PCIe Gen 3 with 8 lanes from the APU feeds wireless and eMMC storage.

Graphics is Radeon R4 with 3 compute cores up to 600 MHz with H.264 and VP9 decode for video playback. Thermal design is board-level with a spreader for the 6 W class and no fan in most chassis.

Upgrade paths

There is no CPU upgrade path from a soldered 9120C. The chip cannot move to a faster part. A board or system replacement is the only move.

For planning, an A6-9220C such as AMD A6-9220C SoC is the faster Chromebook twin at 1.8 GHz with Radeon R5 on the same FT4 lands when the board lists it. The Socket FT4 page lists the Stoney Ridge range.