MSI FM2-A85XA-G65 VRM
MSI boasts the FM2-A85XA-G65 as having “DigitALL” power for the CPU, since it uses a digital PWM for the CPU’s 6+2 phases. I believe this is the first time MSI have used a digital PWM, and it’s interesting that they chose a relatively mid-range board to introduce this feature. I’m not complaining though, because this VRM is actually really good:
Trinity APUs have fewer voltage inputs than Intel CPUs, which is why we see phases listed in “6+2” rather than something like “6+2+1” or whatever. Even though there is an integrated GPU, it uses the same voltage rail as the CPUNB which powers the rest of the non CPU components on the APU (memory, PCI-E, etc).
Therefore, we only have to worry about one PWM for the CPU, and that’s the very high quality International Rectifier IR3567A. This PWM controls 6 true phases to the CPU voltage (shown in red) and 2 to CPUNB (shown in blue).
The green phase you see on the right is a single VDIMM phase, and is controlled by a linear regulator (uP0109) rather than a switching regulator (PWM). This is less efficient than a switching regulator, but for this board it is sufficient. The rail you see at the very bottom is another linear regulated single phase for PLL.
One might have an issue with MSI proclaiming this as “DigtitALL” since not “ALL” phases are in fact digitally controlled (or even switching phases). Other more expensive boards like the EVGA Z75 SLI use digital phases for all rails – even VDIMM and VCCIO. You can tell that this drives the price up though – they had to use three digital phase controllers. Since the most important parts are covered (CPU and CPUNB) I don’t have an issue with MSI, especially since this is their first time using any digital phase controllers at all.
Let’s take a closer look at a CPU phase, since that’s what really matters:
Starting from the left, we have the RJK035J5DPA high side MOSFET, and a pair of RJK035J2DPA low side MOSFETS. Unfortunately we don’t have the datasheets for these components, but we have seen similar hardware used on another board we’re reviewing soon (Gigabyte Z77X-UD5H) which costs a lot more.
These are all low RDS(on) transistors, and are driven by a CHL8550 driver. Current is sent through a solid ferrite choke, before going to a solid state capacitor. Note that the top two phases (the two that do most of the work) also get a Hi-C capacitor. This in itself is probably overkill for this kind of board, so I won’t complain that only 2 of the 6 phases receive the extra attention.
All in all, I have to say that the VRM used on the FM2-A85XA-G65 is quite a bit more than expected for a $100 motherboard. They are using high quality components from the full digital IR PWM for the CPU, low RDS(on) MOSFETs, solid chokes and caps. Just looking at these specs, you can be sure that the VRM will be durable, and should be able to take the Trinity APU about as far as it possibly can on air or liquid at least.
MSI FM2-A85XA-G65 Motherboard Tour
WIth the VRM taken care of, we can go on one of our motherboard tours.
As usual we like to kick things off with the first appearance of The Realtek Crab~! This time he’s on the ALC892 audio codec, along with some capacitors to keep the current clean. Onboard audio is usually pretty much the same, so I always like to see a motherboard include some extra software for tuning. MSI doesn’t disappoint in this regard, and the FM2-A85XA-G65 comes packed with THX TruStudio PRO, which we’ll take a closer look at later in the review.
Apparently MSI couldn’t get enough of The Crab~! so he’s back. This time it’s on the Realtek RTL8111E ethernet controller. We’ll be benchmarking it later as well.
The FM2-A85XA-G65’s Super I/O duties are handled by the Fintek F71889AD controller. This adds the board’s legacy functionality (PS/2 ports, PCI ports) along with its hardware monitoring and fan controls.
There’s one more chip to look at before we move on, and it’s the ICS 9LRS4850AKL clock generator. This allows the PCI-E bus to remain at a stable speed while the CPU BCLK is increased. Normally with the CPU’s internal clock generator, you might get up to 105 MHz or so before running into problems, but MSI say that the FM2-A85XA-G65 can reach upwards of 126 MHz and beyond. This is only of importance to those who decide to overclock their locked CPUs. Most will want to keep their BCLK set to 100 MHz.