Who cares about power supplies? They come with a computer, there is a fan, and they just work. Most of the power supplies that I have that came with computers were pretty decent units. It turns out there are several reasons to care about power supplies. For me, the biggest issue is reliability and efficiency. Having a power supply fail is bad. Having it fail and destroy the rest of the computer is really bad. It hasn't happened to me, but I have read about it happening to others. Most older power supplies aren't very efficient. One clue is they don't specify their efficiency. They are typically 60-70% efficient. What that means, if they are drawing 100w from the AC, then only 60-70 watts end up going to the computer. The rest of the power ends up making heat. This is bad because it ends up costing me more money. What is worse, is the heat had to be removed from the system, and that means fans. Since I don't live in a computer server room, I like my computers and power supplies quiet. The easiest way to get a quiet, reliable power supply is to find an efficient one.
Power supplies draw power from the AC in an odd fashion. Basically, they draw a chunk of power at the start of the AC cycle, and then they draw very little power for the rest of the AC cycle. This isn't a big deal when they are running from the AC line, but is a big deal when they are drawing power from a UPS. There is a way to make their load look 'nicer' and it is called power factor correction. There is active and passive power factor correction. To get really high power factor correction (like 99%) requires active power factor correction. This costs a little more than passive PFC, and actually reduces efficiency by a tiny amount. All the good power supplies have it. If you find a power supply without it, it is either old, or a really inexpensive, lower quality unit.
Some people think that if a 300 watt power supply is good, then a 500 watt power supply is better. A friend needed a new power supply, and I recommended a 380 watt unit. He said the rest of his power supplies were 500 watt, and that 380 was inadequate. I mentioned that he didn't have a case full of power hungry components, and that his computer was likely using under 250 watts of power. My dual Intel Xeon 2.4ghz system, with 6 hard drives draws 182 watts from the wall at 100% CPU usage. I do have a low power video card, and low voltage Xeons, but allowing for power supply efficiency, the computer is taking about 150 watts of power. Hard drives do take more power when spinning up (which is why SCSI drives can be started in a staggered fashion), but clearly a power supply around 300 watts would be find for my system. Now if you have a killer graphics card or two, that can suck up lots and lots of power, and you may actually need a big power supply. Read up on the power requirements of your components before actually buying a high power power supply.
There is more to a power supply than its total wattage. The power supply output is split between several different voltages. There is +3.3, +5, +12 volts. On older atx motherboards, the cpu voltage regulators drew power from the 3.3v rail. It was important to have a high enough current capacity to power the cpu. On newer motherboards, the cpu voltage regulators draw power from the 12v rail.
Generally, hard drives use 12v to power the motor, and can draw roughly 2 amps on the 12v line when spinning up. The power supply must have enough current capacity on each of its voltage lines in order to supply the peak requirements of the computer. I recently had a problem with a dual Opteron motherboard. The problem was my 460w power supply didn't produce enough current at 12v to spin up my hard drives and boot up the two 95w Opteron.
One trick to minimize peak power is to stagger the spinning up of hard drives when the system boots. SCSI drives have generally had this feature for more than 10 years. SAS and SATA drives can do this if the hard drive enclosure supports this feature. My SCSI hard drive enclosure supports this.
Just for a datapoint, I have an Antec EarthWatts 380w power supply powering my dual Xeon lv (@55w for each Xeon) fileserver with 7 hard drives, with no staggered spinup. I did need to adapt the 4 pin power connector to an 8 pin SSI connector.
Purchased around Feb 2007. I bought an Antec SU380 power supply because it was bundled in with their Antec NSK-2400 case. I read a positive review of it at Silent PC Review. It is 80 plus certified, which means it is at least 80% efficient at 20%, 50% and 100% of load. It has active power factor correction and is OEM'ed by Seasonic. Since I already had good experience with my Seasonic SS 460, I was confident it was a good power supply.
The power supply didn't work for my motherboard (a FIC AM37 from an E-Machines computer I got for free). I contacted Antec tech support, and they asked if my motherboard needed the -5 volt line from the older ATX 1.2 power supply standard. I wasn't sure (it turns out that -5 volts is used by EISA pc card slots, which haven't been used for several years), so I clipped the -5 volt wire on my working power supply, and it still worked fine. I told them that it wasn't the problem, and that my motherboard was for an AMD 2000 processor, and the brand and model of the motherboard. They sent me another one that also didn't work.
I tried the original PS out on another AMD 2000 system I had, and it worked! I also tried the old one out on a dual Pentium 933 system I had, and it also worked. So there is something odd about my E-Machines motherboard. I sent Seasonic (the real manufacturer of the power supply) an email asking for assistance, and they told me to ask Antec. I already knew that Antec was pretty clueless about power supplies (clearly demonstrated by them asking me about the -5 volt line, and being unfamiliar with my motherboard). I have never had this problem with a power supply before. I ended up installing the PS in the dual Pentium 933 system. It is pretty quiet.
Purchased around 2007. I bought an Antec EarthWatts 380 power supply because it was inexpensive after rebate. I read a positive review of it at Silent PC Review. It is 80 plus certified, which means it is at least 80% efficient at 20%, 50% and 100% of load. It has active power factor correction and is OEM'ed by Seasonic.
Just like their SU380 power supply, it didn't work for my FIC AM37 motherboard with an AMD 2000. It did actually boot the computer once, when I only attached the motherboard, but it never did with the hard drive and DVD drive attached. I ended up installing it in my other AMD 2000 based system. It is certainly a quiet power supply, but clearly not flexible enough to work on all motherboards.
Well, there have been lots of rebates associated with this power supply. The latest EA-380 I bought was $15 after rebate. The best value 80+ power supply that I know of.
I just ordered my 5th power supply. It was the EA-500. I needed a SSI connector (a 8 pin 12v connector, used for dual Xeon and Opteron systems), and the cheapest decent solution I could find was the EA-500 (the 380 and 430 don't have a SSI connector). For some reason that I don't understand, the SATA power cables on the EA-500 are significantly shorter than the SATA cables on the EA-380. So short, that I had to use adapters to power my four SATA hard drives with them. It was $35 after rebate.
Purchased Aug-25-2012. This was on sale for about $15 after rebate, which is ridiculously cheap for a quality power supply. This was my first 80+ bronze power supply. 80+ bronze means a minimum of 82% efficient at 20% load, 85% at 50% load, and 82% efficient at 100% load. The good news was it cost $11 after rebate (not counting taxes). It also has a 135mm cooling fan. It runs reasonably quiet. The bad news is with such a big fan, the case is quite big. The atx de-facto standard is 140mm depth. This power supply is 160mm deep. Since my Seasonic SS-460 is the standard size and is less efficient, there is no justification for such a big case. The only excuse is that they may use the same case for their higher power models. It is quite a boring power supply, and has caused no issues. The cables are sleeved with black fabric which is a nice plus. For the value, it can't be beat.
Purchased around 1997. My oldest power supply is a 300w hot swap redundant AT power supply made by Emacs (also known as Zippy). They are a well known high end company for power supplies. This features two power supplies, with two separate power cords. You can pull out one of the power supplies while the computer is on (or turn one off), and the computer will keep on running. Redundant power supplies used to be standard on big server type machines, because you can replace a broken power supply without turning off the computer. If a power supply fails, an alarm will sound, and you just pull it out, and put a new one in. I had some Compaq servers that had 3 power supplies that shared the load, and one of which could fail, without bringing down the system. This Emacs power supply has a pretty powerful fan that is sure to keep the power supply cool under adverse conditions. Unfortunately, it predates variable fan speed power supplies, so it is pretty noisy. If someone needs one, it is for sale, cheap.
Purchased around 2003. I had a 300w generic ATX power supply, and I was having a hard time booting and spinning up all my SCSI hard drives. I decided I needed a more powerful unit. Still working in my fileserver computer. I replaced it with a Antec EarthWatts 380 and the power usage didn't go down significantly. Therefore, the Enermax must have been pretty efficient. This is quite remarkable, because the Enermax was built roughly around 2000, when efficiency wasn't considered a big deal. For it to be close to 80% efficient was quite surprising to me. Being an old power supply it has a 20 pin ATX power connector, and no fancy Pentium-4, SSI, or high powered graphics card power connectors, as none of that stuff existed around 2000. It isn't as quiet as newer power supplies. Still, it is my oldest running power supply and I am impressed that the 8 year old hardware is holding up well.
I bought two Gateway 6400 Server computers in June 2002. Servers are supposed to be built of quality parts, and have few failures. One of the computers was having a hard time booting. The fans would spin up, but the computer would not boot (power on self test). Sometimes it would boot successfully. After a few months, it failed to boot. I suspected the power supply (Astek model SA320-3525) might be had. I put in a different power supply, and have not had a problem booting.
I bought this Jul-04-2013 on sale for $14.99 from tiger direct, with a $14.99 rebate making it free after rebate. This is a very plain looking OEM power supply, that is 80+ bronze rated. The case is unpainted metal. The power cables are unsleeved. It has a 80mm fan attached to the back panel. It is vented via holes in the sheet metal. Not as free flowing as a steel wire fan cover. Personally, I think having a fan at the back provides a straighter air path than a 120mm fan on the top of the power supply. Reasonably quiet and boring, just like a good power should be.
I really like lower wattage power supplies. 80+ specs start at 20% load, which is 70 watts (dc) for this power supply. Most simple computers draw about this much power. I fail to understand the need for high wattage power supplies unless you have some very hot running video cards. I am sure the build quality isn't as good as Seasonic or one of the premium power supply makers. On the other hand, it doesn't cost $100. I suspect it is good enough for most usage, including mine.
I sold one to a friend. After a year, it failed. Using my new fancy power supply tester, it only put out 12v and 5v. It also failed to spin up the fan. It had a one year warranty, so I was out of luck. Fortunately, I had 2 more.
Purchased May 2003. Before I knew much about power supplies, I bought this unit. It worked for a few months and then started failing intermittently. After another week or so, it failed completely. Replaced under warranty.
I bought this when I didn't know much about power supplies. Worked for a few months, and then started failing intermittently. Eventually failed completely.
Purchased Dec-26-2012. This was on sale for $45 after rebate, which is a great deal for a 80+ platinum power supply. 80+ platinum is the highest level of efficiency for 120v power supplies (240v power supplies are a bit more efficient and there is a 80+ titanium standard for them). 80+ platinum means a minimum of 90% efficient at 20% load, 92% at 50% load, and 89% efficient at 100% load. 80+ platinum power supplies are often higher power, which is useless for me, as my computer typically operates below 20% load for a 450w power supply.
It also has a 135mm cooling fan. It runs reasonably quiet. The bad news is with such a big fan, the case is quite big. The atx de-facto standard is 140mm depth. This power supply is 163mm deep. Since my Seasonic SS-460 is the standard size and is less efficient, there is no justification for such a big case. The only excuse is that they may use the same case for their higher power models. Looking inside, there seems to be about 2cm of empty space on the inside edge, and about 3cm of empty space on the outside edge (except for the AC power protection circuitry). It is clear it could easily be packaged smaller if it had a 120mm fan. I strongly recommend it have a smaller case, to fit inside more cramped cases. It is rated at full power at 50 degrees C (which is what all power supplies should be rated at, but the cheap ones are not). It also has a 7 year warranty, which is quite long for a power supply. Seasonic power supplies (which I consider the gold standard of power supplies), have a 5 year warranty. At 10% load, this model is 85.99% efficient according to the 80+ test report. At 20% load it is 91.30% efficient.
One issue I noticed when installing is the two parts of the 20+4 pin power connector doesn't stay connected to each other. I am used to the Antec style power connectors that clip together, and become one unit. I ended up zip tieing together the 2 end wires of the 20 pin connector with the 2 end wires of the 4 pin connector. Without doing that, the 4 pin connector didn't stay seated. Really a bad design for Rosewill.
It is difficult to justify the extra cost for a 80+ platinum power supply over a plain 80+ power supply based on cost savings. However, they will use less power, are generally quieter, and will make less heat. The higher the power your computer needs, the more expensive your electricity is, the more hours per day your run your computer - the easier it is to justify. For systems running 24x7 in a dense configuration, it is easy to justify the extra cost. Platinum power supplies may use higher quality parts or be more reliable than less expensive power supplies. I waited for mine to be on sale, because I am frugal.
Purchased around Aug 2004. When I built my Dual Xeon system, I needed a 24 pin ATX power supply, with a SSI connector (used for dual Xeon and Opteron systems). Seasonic wasn't well known at the time, but they had the most efficient power supplies around. They were claiming 80% efficiency before the 80+ organization was around. I bought it. Very boring, very quiet, very reliable. When it is under light load, the fan stops spinning (it has a fan rpm sensing output). All power supplies should be like this.
Ultra Products makes several power supplies. I have a few that I got free after rebate. Some are somewhat plain looking, but most look really cool. Most are not plain sheet metal, but painted to look cool. One of my units features 'modular' connectors, which means you can unplug unneeded cables. Each modular cable is sleeved and green, and I think they glow under UV lighting. I am not so impressed with modular cabling however. The extra connector has some resistance and adds another possible point of failure. What is novel is that some of their newer models have the cables attached to each other, like a 2 conductor AC power cable. Ultra calls it 'flexforce'. This is simple and much cleaner than 4 or 5 individual wires. They even introduced a 80 plus model. All of mine work. All of them are relatively low efficiency. Some of them (even the ones with variable speed fans) are noisier than they should be, though no nosier than a typical low efficiency power supply. The newer ones with 120mm are quieter than their older ones.
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