A Detailed Look (Cont’d)
Here are a few pictures showing the layout and components inside the HX620W power supply.
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620 Watts continuous load…
Most typical users have little idea about the true power requirements of their particular system. It might come as a surprise that the majority of modern PC’s actually use less than 200 watts of power (75% efficiency x 200 watts AC in = approximately 150 watts DC load). For example: I used a WattsUp? Pro power meter to measure the AC power consumption during idle, CPU load, and gaming conditions of a modest PC consisting of the following components.
- Epox EP-9NPA nForce4 Ultra motherboard
- Athlon 64 3200+ (90nm) CPU
- (2) Corsair 512 MB XMS 3200XL low latency RAM (2-2-2-5)
- Leadtek GF6600GT PCI-e 128 MB video card
- Western Digital 120MB Serial ATA HDD
- Sony 16X DVD DDU1612
- Panasonic DVD/CD Writer DVR-108 dual layer
- FDD and Universal card reader
- (2) 120mm low-speed cooling fans
System idle (sitting at Windows XP desktop) 112 watts
CPU full load (Folding@Home) 139 watts
Gaming benchmarks (3Dmark) 158 watts
I also measured the current flow going to the motherboard thru the +3.3V, +5V, +12V main and +12V aux lines with a FLUKE ammeter.
So why then you might ask, would we need a 620 watt power supply? For one thing a power supply should ideally be rated for approximately twice the expected maximum load. If your PC will use between 150~200 watts of DC power then the PSU should be rated for at least 350~400 watts. This will allow the power supply to operate at around 50% of its rated capacity. A power supply only delivers as much power as is required, so just having a high capacity PSU won’t cost more to operate. It may in fact be more efficient to operate and will most likely allow the power supply to operate much more quietly than pushing it to its maximum capacity.
But if you are a gamer with one or more high-end video cards, then you will definitely need a high-quality, larger capacity power supply! For example: BFG Tech recommends using a power supply that can deliver a minimum 26A +12V with their GeForce 7800/7900 video cards. If you have two GeForce 7800/7900’s in SLI mode, then a minimum rating of 34A +12V is recommended. That’s over 400 watts for just the two video cards. The Corsair HX620W power supply is designed to handle these types of loads.
In the past, the majority of PC enthusiast didn’t worry too much about their power supply — generic was frequently good enough. For the most part those days are gone. To operate a modern gaming rig or workstation today requires more thought and a greater investment to insure reliable operation.