MSI MAG A850GLS PCIE5 ATX v3.1 PSU Review

Protection Features

OCP (Normal @ 28.6°C) 12V: 86.80A (122.60%), 11.937V
5V: 30.8A (154.00%), 4.969V
3.3V: 31.6A (158.00%), 3.35V
5VSB: 5.7A (190.00%), 4.918V
OCP (Hot @ 40.8°C) 12V: 87.70A (123.87%), 11.941V
5V: 29.9A (149.50%), 4.964V
3.3V: 29.8A (149.00%), 3.341V
5VSB: 5.6A (186.67%), 4.901V
OPP (Normal @ 28.1°C) 1032.67W (121.49%)
OPP (Hot @ 42.0°C) 1032.72W (121.50%)
OTP ✓ (115°C @ Heat Sink)
SCP 12V to Earth: ✓
5V to Earth: ✓
3.3V to Earth: ✓
5VSB to Earth: ✓
-12V to Earth: ✓
PWR_OK Proper Operation
UVP (Full Load @ 90V)
UVP (Damage @ 80V)
Conducted Emissions EN55032 & CISPR 32
NLO
Fan Failure Protection
SIP Surge: MOV
Inrush: NTC & Bypass Relay

The 12V rail’s OCP triggering points are set conservatively, but this doesn’t mean that they are correctly set. At high temperatures, 12V OCP is higher than the corresponding setting at normal temperatures. Normally, it should be the other way around. The OCP points on the minor rails are lower at high temperatures, but in general are very high, especially at 3.3V. Lastly, the over power protection has similar triggering points under normal and hot conditions, high temperatures, which is not correct, of course. The rest of the essential protection features are present, except for fan failure, which is not typically found in most desktop power supplies (unfortunately).

EMC Pre-Compliance at a Glance

Every electronics device, including PSUs, can be an EMI source, which, depending on the amount of EMI emitted, can affect the proper operation of nearby devices. EMI can, in some extreme cases, even render them unusable. Some standards have been established to minimize electromagnetic interference (EMI) noise. The corresponding standards for IT (Information Technology) products are CISPR 32 and its derivativeEN 55032, which applies to products sold in the EU. In the EU, every product bearing the “CE” marking must comply with the EN 55032 standard. CISPR 32 and EN 55032 standards categorize devices into two classes: A and B. Class B equipment is intended for domestic environments. Hence, its permitted EMI emissions are significantly lower than those of A-class devices.

Our equipment for EMI readings:

  • Rohde & Schwarz FPC1500 (loaded with all options)
  • Tekbox TBLC08 LISN
  • Tekbox TBFL1 transient limiter
  • Tekbox EMCview software
CISPR 32 / EN55032 Limits
CISRP 32 / EN 55032 Class A Conducted EMI Limit
Frequency of Emission (MHz) Conducted Limit (dBuV)
Quasi-peak Average
0.15 – 0.50 79 66
0.50 – 30.0 73 60
CISPR 32 / EN 55032 Class B Conducted EMI Limit
Frequency of Emission (MHz) Conducted Limit (dBuV)
Quasi-peak Average
0.15 – 0.50 66 – 56 56 – 46
0.50 – 5.00 56 46
5.00 – 30.00 60 50
CISRP 32 / EN 55032 Class A 10-Meter Radiated EMI Limit
Frequency of Emission (MHz) Field Strength Limit (dBuV/m)
30 – 88 39
88 – 216 43.5
216 – 960 46.5
> 960 49.5
CISRP 32 / EN 55032 Class B 3-Meter Radiated EMI Limit
Frequency of Emission (MHz) Field Strength Limit (dBuV/m)
30 – 88 40
88 – 216 43.5
216 – 960 46.0
> 960 54.0

Please note that the ATX spec allows a 4 dB margin for conducted and radiated emissions. This means that if a PSU exceeds the limits but stays within the 4 dB margin, it meets the corresponding ATX spec requirement (8.1 Emissions).

EMI Results

The PSU’s conducted emissions are below the respective limits at both the average and peak EMI detectors.

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