Besides being modular in design, the HCG-620M shares the same specifications as the HCG-620. Both have a single 12V rail rated for 48A in addition to 3.3V and 5V rails rated for 24A. The combined maximum output of the minor rails sums to 130W, while the main rail supplies a maximum of 576W. Being able to output a substantial amount of power from a single high capacity 12V rail as opposed to spreading it around three or four weaker 12V rails is what makes this 620W PSU perform like a unit with a higher rating and price tag. Many testers from around the web have praised the HCG-620M for its solid performance across all rails under full load, with voltage variations never surpassing 2%.
I installed the HCG-620M in a Cooler Master HAF-XM Mid Tower to fully appreciate its modular design and stealthy wires. I did find myself running out of slack in a few places, most notably the 20+4-pin and ATX12V/EPS12V power cables. The SATA and Molex cables were also quite stiff. The HAF-XM isn't sized like an average mid tower, but I would advise double checking your reach before attempting an installation in a larger full tower like a HAF X or CM Storm Trooper. The dual purpose 10-pin sockets are very convenient to have, as they offer builders an added level of flexibility in how they manage their cables. The bold red logos may look great at first glance, but they actually cause a clash between form and function. Those who build in today's modern chassis with bottom mounted PSUs and place a high priority on proper cooling and airflow may prefer to mount their HCG-620M upside down. This would allow the intake fan to pull fresh air from underneath the case, but it leaves Antec's pretty logos and text looking not so glamorous. It would have been wise on Antec's part to flip the orientations of their exterior designs on opposing sides of the PSU enclosure, much like the OCZ Fatal1ty 1000W we reviewed earlier. This would ensure that the text is facing the right way up no matter how the user chooses to orient the intake fan.
Given its 80 Plus Bronze certification, modular cabling, cable sleeving, and a host of protections, the HCG-620M is very well equipped. It does however lack over temperature protection. It isn't all that uncommon to find a power supply with no over temperature protection, as it is considered optional. There is no indicated temperature rating for the HCG-620M on Antec's website, however a quick web search reveals that this PSU is indeed capable of delivering continuous power at ambient temperatures above 50°C. One of the biggest selling points of this PSU is its usage of Japanese capacitors, which are notorious for their above average electrolyte and sealing. The HCG-620M uses a mix of Nippon Chemi-Con and Rubycon capacitors rated at 105°C. As it turns out, the High Current Gamer Series as a whole shares a vast amount of parts with a number of Seasonic PSUs. The HCG-620M is nearly identical in construction to the Seasonic M12II-620, aside from some small differences in its circuit board. Seasonic has a reputation for developing some great power supplies, so it should come as no surprise that the HCG-620M is a good performer.
Antec included a noise graph on its packaging for a reason. The 135mm double ball bearing fan in the HCG-620M is extremely quiet. In fact, its operation is nearly imperceptible when listened to outside of an enclosure at low load. The average CPU cooler or case fan should easily mask the noise emitted by the HCG-620M, even when it is under load for extended periods. Due to a lack of proper testing equipment, we are unable to report an accurate decibel reading of the fan's operation under load. Antec claims a mere 14dBA under 10% to 50% and a maximum noise level of 30dBA under 100% load. The nine bladed fan is also equipped with a plastic baffle to effectively direct airflow.