Modular vs Hard-wired... which for your high-end rig?

[Richdog]

After the Dual rails thread I figured that while we are here we may as well get another discussion out of the way, as I have heard people asking about it and I myself would like this clarified.

Hard-wired vs Modular... is hard-wired the better option for a stable high-end PSU?

First I will draw on the website of what is widely regarded as the best quality PSU maker in the lands... PC Power & Cooling. On their website, PCP&C state re: modular PSU's: http://www.pcpowerandcooling.com/about/interview.php

CPU: Modular power supplies seem to be gaining a lot of traction in the market, but PCP&C doesn’t make any modular designs. Why?

Dodson: Yeah, it’s real popular, but the industry hasn’t done anything to educate people about modular plugs. The pins that are used in the modular plugs have a very low capacity to pass current. You’re losing power through those pins. It’s electrical resistance between the male and the female part of the pin, to the extent that the voltage drop in just the pins is equivalent to about two feet of wire. The effect is that modular power supplies, everything else being equal, are capable of about 10% less power than power supplies without modular plugs. And that’s under ideal conditions. In real life it gets worse because the pins loosen, corrode, and burn. Over time the resistance builds up. A year down the road, a guy could be running his system and all of a sudden it stops working reliably, and he has no way of knowing that the reason is because the pin inside that modular plug has become corroded or burned. This technique has been out for about six months, but people are going to find that the reliability is a massive failure point. Also, especially given the way people pull their harnesses around and tie them down, it creates a lot of stress on those pins. So instead of the pins having full 100% contact surface to surface, in most cases those pins are only touching maybe 10% or 30% of their surface area. What’s rated for 5A going through those pins, in reality if the pins aren’t making good contact, your rating’s down to maybe 3A, and with that much constriction, those pins just heat up, and it gets worse. For real pros in the industry, no way would they specify that kind of arrangement. This is a consumer-oriented gimmick.

Now as I said previously, I am no expert and would consider myself less the averagely informed about PSU's, but that doesn't particularly endear me to buy a modular. When I am looking for something to power my $2000 PC I am looking for something that isn't describes using the terms: "reliability is a massive failure point" or "A year down the road, a guy could be running his system and all of a sudden it stops working reliably".

Is this a reflection of modular PSU's in the past, or do they still suffer from that problem?

Another explanation I heard on another forum for the downside of a modular PSU was this:

Simply, Ohms Law : V=IR

Any soldered joint will have a lower electrical resistance than a similarly sized connecter, particularly if the connecters mating surfaces are not prefectly clean or slightly loose.

This isn't an issue if the joint/connecter does not need to carry much current, for example in signal level applications. However, when moving large amounts of current around, resistance in wires, joints and connecters becomes increasingly important.

Take a fictitious situation where you're powering a load from a 12V DC supply, and this load is quite power-hungry, drawing ~10Amps from the 12V source.

Say you used a connecter to connect the supply and the load - you'd need two connecters (one in the +12V line, the other in the ground line), each having a resistance of say .05 ohms.
This means you'd be dropping ~500mV across each joint, leaving the load with only ~ 11Volts.

If, on the other hand, you'd used nice soldered joints instead of the connecter, the resistance of the joints might be only .01 ohms apiece meaning the load is only losing 200mV, leaving it with 11.8Volts.

Reducing voltage drop and heating due to connecter and wire resistance is the main reason there are multiple red, black and yellow wires used to carry current from the supply to the mainboard (the load) in PC's.

Also, a manky or loose connecter carrying a lot of current is going to heat up and quite possibly cook itself in short measure.

This doesn't mean A power supply which adds a 2nd set of connecters in addition to the ATX one is useless. It just means you're adding another point where you're going to lose a small, but possibly important amount of voltage that chucks your highly overclocked system into instability.

That suggests to me that adding the modular connector point further decreases efficiency and reliability of the PSU in comparison to one that is hard-wired.

So, in the opinion of those out there who know their power supplies... what truths do the above quoted information hold, and would you be able to put the fears of more simple PSU folk like myself to rest about the thought of going with a modular PSU over a hard-wired?

Rich

[Ishy]

Originally Posted by Richdog

Is this a reflection of modular PSU's in the past, or do they still suffer from that problem?

Most modular designs still suffer from this, the only real exeption is the Enermax Liberty range, they're the only modular PSUs that i would use to power a very high end system.

[mgv101]

Remember, you allready have one connection along each line you use anyway as it is needed to connect the line the components needing the power. With a modular PSU, you are just putting a connection in both ends of your connection rather than having having just one at the very end.
As there has always been a connector present anyway adding an extra one shouldn't hurt it too much.

It is important that the connection must be good though as I have fallen victim to a bad connection myself on my old power hungry P4 prescott setup where the plastic connector on my 12V connector had been fried on the mobo. I ended up soldering the wires straight onto the back of the board as the socket was no longer usable. If it was able to burn the plastic in the plug, there must have been plenty of resistence in the joint.

Maybe we will see gold plated pins in the future on the modular connections. As I heard that gold plated pins will lower the resistence significantly.

Anyway, I prefer hard wired PSUs myself as I find no need of a modular supply. I am able to tuck the un-used lines away eaisily and I don't even see them at all or have them getting in my way. So why add extra resistence if you could avoid it? This is especially true when there are people out there (me included) who would spent $200 on a power supply over a $150 one where in reality the $200 PSU would only perform marginally better.

[jonnyGURU]

No doubt, hard wired is better. Absolutely no doubt. Just take a look at two power supplies that are absolutely identical in every way except for the modular connectors: The Ultra X2 and the X-Finity for example. V fluctuation on the X-Finity is less than 2% across full load and as much as 4% on the X2.

There are worse examples: The Topower/Tagan Tiger 550W modular fluctuates more than 5% from idle to load. SCARY!!! But all along, still within the 5% spec from center.

The Enermax is simply a wicked exception. I think they hired aliens to help them with that model.

But regardless.... the voltages are always, on any of these units, still within spec. Even the drop in voltages at high loads caused by the resistance of modular connectors is still totally acceptable. And since the loads in a PC won't be a static load to a sudden static high load like you see on a load tester, the fluctuation of voltage is even less noticable.

PCP&C also brings up a good point.. in theory... or potential corrosion. I don't know about you, but my PC isn't kept out in the lanai all summer. If corrosion of the modular connectors is a concern, then corrosion at the connection at the motherboard, drives, etc. should be a concern as well. Connections that ALL power supplies have whether they're modular or not. And for that matter, let's talk about interfaces that are even smaller and more sensitive to corrosion: DIMM slots, PCI-e slots, CPU socket.... Aren't these at least as succeptable to corrosion as a Molex?

I think if you're aware that the PSU costs a premium because of the modular connectors/cables and you're aware of the lower overhead because of the modular cables (The Silverstone ST65F and ST60F are actually the same PSU inside, but they drop the max wattage 50W off the label simply because of the modular aspect) then there's nothing wrong with getting a modular power supply.

[Richdog]

So Jonny do you consider the Enermax Liberty 620 the best modular PSU there is? What are it's major plus points in comparison to other modulars?

[jonnyGURU]

Originally Posted by Richdog

So Jonny do you consider the Enermax Liberty 620 the best modular PSU there is? What are it's major plus points in comparison to other modulars?

I think it's safe to go on record as saying that. That and the Silverstone ST60F. Easily a contender for stable rails. We can't foget the Silverstone and if you have any doubts, take a look at the top five PC's in the Futuremark Hall of Fame. All have Silverstone quad-rail PSU's. The ST-60F only falls short of the 65F > 600W.

[Panthols]

I'm looking at the Hiper and the 24pin connection is hard wired... wouldn't that make the connection going to the MB (guessing the most important one) just as stable as a standard PSU? Or does the modular design effect the voltage across the board, and cause even the hard wired connections to fluctuate more?

[Player0]

My OCZ ModStream works wonderfully. The main power wires arent modular, the ones that carry all the current.

Energy on bad connections is turned to heat. So if the connection is that bad, the molex ends will probably char. Heck, they tend to do that on their own sometimes on regular PSUs. If the wires/connectors arent getting that hot, it doesnt matter.

The device itself is going to draw the same amount of current. The PSU might have to work harder to provide the 110% (10% to the resistence load, 100% to the device being powered). Volts may drop a little, or maybe even fluctuate under high enough loads.

Voltage tolerances are generally pretty high as long as the fluctuations are stable. The motherboard/video card filter their own power anyway. So if connectors arent overheating im not sure they would make much of an issue otherwise.

Im not sure the devices are ever starved, its probably more of a fire issue

[jonnyGURU]

Originally Posted by Panthols

I'm looking at the Hiper and the 24pin connection is hard wired... wouldn't that make the connection going to the MB (guessing the most important one) just as stable as a standard PSU? Or does the modular design effect the voltage across the board, and cause even the hard wired connections to fluctuate more?

No. The hard-wired connectors will give you a different voltage reading than the modular ones.

Too bad they don;t fix the PCI-e connectors too.

[jonny]

The mobo connector is hard wired because that is the main power for the cpu and all else so it has to be stable but the others its not so much so wont make too much of a difference going modular???? The hiper 580W i want has screw on ends so i dont have to worry about pins loosening etc.

[Josie Wales]

I think the truth lies somewhere between the casual "it really doesn't make a difference" and the "In real life it gets worse because the pins loosen, corrode, and burn" statements. In most climates it is rare to see corrosion on any on the molex connectors or motherboard contacts, let alone the more exposed DIMM slots, PCI-e slots, and CPU socket as JonnyGuru points out, or most importantly, the modular main power cord that carries all of the wall current to the power supply. And seriously, if loose pins is such a problem why do most firms only crimp them to the wires? The key is a properly designed and constructed connector. With a well designed connector it becomes a simple engineering problem to overcome a small amount of resistance and provide stable power. Most modular power supplies are adequate for office machines to entry lever game machines. Some even perform well enough for enthusiast rigs. Remember that PCP&C provides a 5 year warranty on the Modular Turbo-Cool 510 ATX.

Having said all this, I would be reluctant to select a power supply that used a modular motherboard or modular 4-pin power connector on any of my performance PCs. That includes adapters or extenders. I occasionally go a bit further than most people by actually shortening some wires and adding a drop of solder to pin crimps.