MSI MPG A850G: One of the first ATX 3.0 PSUs in detail

MSI MPG A850G PSU (850 W)

Power supplies with support for the latest ATX 3.0 standard are slowly increasing in numbers and we will make some order among them – by pointing out the “better” and “worse” models. Based on this, you will then be able to choose the one that you consider to be more advantageous with regard to the price and to the use case. We’ll start lightly, with a brief analysis of the 850-watt A850G, by MSI.

Disclaimer: This article does not contain tests, but only a kind of preparation for them. We do not have (and will not have) our own equipment for testing power supplies, but by the end of the year we could get to a specialized laboratory where everything needed to analyze the relevant electrical quantities is available. Until then, we will collect a few models (mainly and maybe only with ATX 3.0 standard support), which we will first take pictures of, analyze their design details a bit, make an overview chart of the parameters and later we will confront each other qualitatively, from the power supply point of view. This will be a matter of unique measurements.

From the outside…

The MSI MPG A850G power supply, despite its high wattage (850 W), has a relatively short chassis, which does not outgrow the shortest ATX power supplies too much. At 150 mm, this PSU is only 10 mm longer. At the same time, it already uses an extra-large 135 mm fan, which, compared to variants with proportionally smaller size (typically 120 mm), ensures higher airflow at comparable noise level, thus it is characterized by higher cooling efficiency.

The grille in front of the fan could probably be more aerodynamic than it is, but even so, it won’t increase noise as significantly as designs with a traditional hexagonal pattern. And it obstructs the airflow less for the larger open area for sure.

In terms of the basic efficiency categorization, it is “only” an 80 Plus Gold certified model, but within the ATX 3.0 standard, higher efficiency is already required. Especially at very low load, where many users spend a significant amount of time. These are typically web browsing, light office work or video watching situations. These power supplies (versus ATX 2.x) also need to be better prepared for the higher current spikes that occur with today’s hardware. The A850G power supply should handle peak loads of up to 141.6 A on the 12V branch for 100 µs, double the claimed continuous (70.8 A) current load. You will find out if the power supply meets these specifications in the tests.

   

The higher current peaks are mainly due to graphics cards, for which ATX 3.0 power supplies also have a native 16-pin connector (12VHPWR). This is used so far only by more powerful graphics cards (from RTX 4070 Ti upwards) with Nvidia Ada Lovelace GPUs. This connector has all the parameters to be eligible for loads up to 600W, i.e. also for the GeForce RTX 4090. Its wires have a large cross-section – 16 AWG (1.31 mm2), which will result in lower temperature at the same current than on connectors with a smaller cross-section. For external power supply of graphics cards, however, there is 16 AWG everywhere, even on 6+2-pins.

Smaller cross-section of wires (18 AWG) is on CPU power supply cables (but you can connect two of them on boards where you run a powerful processor and thus reduce temps) and on SATA/Molex cables, for which there are always very low currents. In these cables, although there is only one wire per branch, 18 AWG is still enough – it’s still an above-average cross-section.

   

The temperature of the GeForce RTX 4090’s 16-pin connector housing at 440W ends up at a pleasant 56.4°C (measured in the traditional wind tunnel conditions we use to test graphics cards).

Owners of Radeons or older graphics cards (other than GeForce RTX 4000) may also be interested in the ability to use the 12VHPWR connector to connect two 6+2-pin PCIe connectors. There are then up to six of these in total, four of which are native connectors. Most of the cables are flat, the only exception being cables with 12VHPWR connectors.

… and from the inside

The use of a 135 mm fan has already been mentioned, but it should be added that this is a 2300-rpm model with a powerful motor (0.5 A) and liquid bearings. According to MSI’s internal chart, high speeds should never be reached. At 100-percent load, the speed is supposed to end just above 1400 rpm. Meanwhile, up until 40% load (i.e. up to 340W), passive operation is promised in the case of the active Zero Fan mode (which is activated by a button on the rear, near the power switch). Otherwise, outside of semi-passive mode, the fan always runs, although up to half load its speed should be constant at about 460 rpm.

On the primary part, where the DC current comes in, there is a large, 400 V capacitor with a capacitance of 680 μF. This is a Nippon Chemi-Con (KMR) “105-degree” model with a low ESR number, which is a sort of quality index (the lower the number, the better). We will not argue about the (in)qualities of the design. Apart from the fact that we do not have adequate experience or the necessary qualifications for this, all that matters will eventually be revealed by the measurements of the electrical quantities, which are a perfect mirror of the qualitative characteristics of the components used.

For a basic overview, it is also worth mentioning that the smaller capacitors behind the main transformer (i.e. on the secondary part to regulate the voltage on the individual branches) are Nichicons. These are also among the best things to put in computer power supplies.

   

The large heatsinks (in the header photo) on the voltage regulators of the converters are also worth praising.

* We report the number of PCI Express connectors as the sum of native and shared ones (the second number after the “+” sign). Native connectors are those that are the same on both sides. Shared ones are then connected via different connectors on the power supply side, for example, a single 300-watt 16-pin (12VHPWR) is formed by using two 6+2-pin connectors, and vice versa – a 16-pin connector can be used to connect a cable with two 6+2-pin connectors.
Important to note: Power supplies are and will continue to be a marginal topic for us, so don’t expect us to go into as much detail about them as we do with other components. The goal, of course, is to be able to choose your favourite based on the basic characteristics. Efficiency at different load levels, the effect of electrical power on voltage drop or its output ripple, we will map it all out. And perhaps, if there is interest, we will also devote space to a frequency analysis of the sound of the coils. But you’ll have to wait a while for the results of any tests.

English translation and edit by Jozef Dudáš


  •  
  •  
  •  
Flattr this!

The Ventus 3X (RTX 4070 TiS) case: Final vs. original VBIOS

The GeForce RTX 4070 Ti Super Ventus 3X graphics card came out with a BIOS that MSI (and even Nvidia) wasn’t happy with. After the second revision, there is the third, the last revision of the BIOS. This one increases the power limit to allow higher GPU clock speeds to be achieved. However, this comes at the cost of a bit lower power efficiency. To update or not to update? That’s for everyone to decide for themselves, if they get the chance. Read more “The Ventus 3X (RTX 4070 TiS) case: Final vs. original VBIOS” »

  •  
  •  
  •  

MSI officially about RTX 4070 Ti Super 16G Ventus 3X faults

MSI has released a statement saying that the RTX 4070 Ti Ventus 3X graphics cards did indeed come out with an untweaked BIOS that prevents this graphics card from achieving its maximum performance. However, there seems to be a fix already that could solve everything. Still… let’s revisit this topic and try to sort through the possible technical reasons that cause the significant fluctuation in the performance of the cheapest three-fan MSI RTX 4070 Ti Super. Read more “MSI officially about RTX 4070 Ti Super 16G Ventus 3X faults” »

  •  
  •  
  •  

MSI RTX 4070 Ti Super 16G Ventus 3X: Big cooler w/o a markup

The biggest hardware changes compared to non-Super cards concern the GeForce RTX 4070 Ti Super. What’s different is the GPU, the amount of GDDR6X memory or the width of the memory bus. We have the RTX 4070 Ti Super in one of the cheapest non-reference designs, the Ventus 3X, for analysis and it will be about “reputation repair” as well. MSI has tarnished it a bit in this line of graphics cards in the past, but now it’s a very attractive solution. Read more “MSI RTX 4070 Ti Super 16G Ventus 3X: Big cooler w/o a markup” »

  •  
  •  
  •  

Leave a Reply

Your email address will not be published. Required fields are marked *