I haven't gone through this entire thread, so, although I've seen some dissent on the original TC's argument, it's not very much, so, I'm not sure how redudant I am being here.
It's not so much that the TC is wrong, as he is irrelevant. And I detect a lot of bias. He’s touting facts that everyone is already aware of as if they are not aware of it.
Of course multi-rail psus are “safer” than single rail... everyone has always known this. How much safer? Are you looking at a 0.001% chance of a fire vs a 0.0001% chance? Who really cares? Either way, multi-rail is not “perfect”, and depending on the cause of the failure (which, more likely, would come from an external source such as a lightning strike), nothing can completely prevent a psu from starting on fire.
The fact of the matter is his discussion is leaving out the important piece of the puzzle as to why many choose single rail over multi-rail. It has nothing to do with safety, nothing to do with “cleaner” or “better” power. It has to do with the fact, that, in the real world, on average, when you see a power supply at Newegg, if it’s multi-rail, none of the 12v rails provide much amperage (A) on either of the rails. Most often, the best multi-rail psus you see have 19 A or so on each rail. But more often there is something like 19A on one rail and 14A on the other rail. This pretty much makes SLI an impossibility – and this is precisely why my previous Ultra, multi-rail psu, started failing and making a high-pitched whine sound after a couple of months. There was literally way too much stress on that second rail.
Besides the fact that when you have the rails split up the amperage like that, you have to deal with the real-world physical constraints of how long or how many each of the cables are on each rail. I remember on my Ultra I couldn’t equally split everything up along the 12V rails because one of the rails didn’t have a connector long enough to reach my DVD player.
The guy then uses an often-unrealistic scenario to try and make it seem like there’s no practical advantage of single rail over multi-rail. Yes, if you have a 1600w psu, it would probably be better to have a multi-rail one. Duh. Each rail is probably going to be at least 40 A on it’s own, which will be just enough for dedicating a rail to each gpu. But, unless you start seeing multi-rail psus that have 40A on each rail (which you won’t until you get into 1600W psus lol), then, for gaming, multi-rail is just a pain in the ass. Personally, I’d love to have a multi-rail psu with 40a on each rail. Personally, I wouldn’t want to spend $300 to own that, however.
On the flip side, the more amperage you put onto a single rail, the more unsafe it (or at least, the more catastrophic the potential) becomes. This is also common sense and is obvious, and pretty much everyone already knew this. My psu has 58 A on its single rail. I have had a mindset that 60 A or so is sort of the “limit” on what would be considered “safe” in the event of a failure. If you start packing any more Amps on that rail, well, then, yes, things may become unreasonably safe (how did I come up with this? It's not scientific. But then again, fire failures aren't going to happen with scientific precision either). And what’s more, if you have more than 60A on a single rail, you’re getting to the point where you can start splitting those Amps up onto different rails.
What’s better, one rail at 40 Amps, or two rails at 20? Obviously, the first choice.
What’s better, one rail at 60 Amps, or two rails at 30? The situation is less clear here, although, if you want to do 2 5980s in crossfire, probably the first choice.
What’s better, one rail at 80 Amps, or two rails at 40? Now, obviously, it’s the second choice. There’s simply no need for 80 amps on a single rail. There are no gpus with a single power connector that would require that much power ever.
But again, this has always been the logic as to why single rail is better than multi-rail, because most people buy psus less than 750 W. Although, this guy is trying to make it sound like single rail was better for other (non-existent) reasons, such as “better” overclocking or something. The bottom line is, most gamers do not have a need for 1600 W power supplies (as most do not do 4-way SLI), and so, in the real world, for most gamers, given the nature of amperage allocation, single-rail psu wins over multi-rail.
Edited by hannedog - 2/19/11 at 9:07am