MSI 890FXA-GD70 Motherboard

Voltage Regulator

MSI added a high-end voltage regulator circuit on this motherboard, featuring five phases, four for the CPU main voltage (VDD a.k.a. Vcore), and one phase for the CPU VDDNB voltage (memory controller, HyperTransport bus controller and L3 memory cache). Therefore it uses a “4+1” configuration.

Comparing only the number of phases is unfair, though. Each phase from this motherboard switches at a higher frequency (1 GHz instead of 250 MHz) and has a lower switching loss, resulting in a higher efficiency and lower operating temperature. This is achieved by using an integrated circuit (Renesas R2J20604) called DrMOS instead of discrete transistors. According to MSI each DrMOS phase is equivalent of four regular phases, so the “4+1” configuration used by this motherboard is comparable to a “16+4” configuration using the standard voltage regulator architecture used by competing products.

If this was not enough, MSI decided to use military-grade components on the voltage regulator circuit. Electronic components rated as military-grade have a higher operating temperature range, tighter specs and higher life-span. All electrolytic capacitors used on the voltage regulator circuit are SMD (surface mount device), also known as highly-conductive polymerized or simply Hi-c, and solid ferrite chokes, which MSI is promoting as “icy chokes” or “super ferrite chokes” (although they are not so impressive-looking like the ones used on Big Bang XPower). According to MSI these chokes work  20° C cooler than traditional chokes. Please read our Everything You Need to Know About the Motherboard Voltage Regulator tutorial for more information.

Capacitors used outside the voltage regulator circuit are solid.

As you can see in Figure 7, there is a big passive heatsink on top of the integrated circuits of the voltage regulator circuit, which is connected to the passive heatsink used on the north bridge chip through a heatpipe.

Figure 7: Voltage regulator circuit with the heatsink.

Figure 8: Detail of the SMD capacitor, solid choke and phase integrated circuit.

Besides having a high-end voltage regulator circuit, MSI 890FXA-GD70 can disable phases from the voltage regulator circuit as needed in order to save energy, feature called APS (Active Phase Switching). A group of LEDs near the memory sockets indicate how many VDD (i.e., Vcore) phases are active at any given moment. The motherboard also has LEDs to monitor the number of phases being used on the south bridge chip voltage regulator (which is a standard two-phase design), and on the memory voltage regulator (which is a standard two-phase design).

Figure 9: LEDs to monitor the number of CPU phases being used.