ASRock X399 Taichi Threadripper TR4 Motherboard Review

Circuit Analysis

The X399 Taichi shows us what it's got under the hood when we remove the heat sinks and shields.

The VRM for the core VRM is a true 8-phase VRM. It's controlled by International Rectifier's IR35201 in an 8+0 phase PWM configuration. Each phase uses a 60A IR3555 fully integrated PowIRstage power stage, which contains the high-side MOSFET, low-side MOSFET, and driver. The inductors are rated for 60A, and the main VRM uses multiple POSCAP tantalum capacitors on the back side of the PCB for its LC filter.

The SoC VRM consists of three phases made up of the same components as the CPU core VRM and is controlled by an IR35201. Each memory VRM uses a UPI Semiconductor uP1647P PWM to control and drive two SinoPower SM7341EHKP dual N-Channel MOSFETs.

Each set of 4-DIMMs is powered by the two phase SinoPower/uPI semiconductor VRMs. There are also three other power circuits that use linear regulators (rather than switching). The Richtek RT8065 are used as 3A linear regulators, for minor CPU voltage rails.