using extra P4 12v line

[Biosylum]

What I ask - has anyone come across info about ppl making alternative use of an unused P4 connector on an ATX12V PSU. I realize most ppl do not have dual, separate +12v rails, so there would be no benefit to manufacturing an adapter, over using a regular molex splitter on a single rail PSU.

Why I ask -purchased Antec Neopower480 based upon company reputation, and that it provided (2) +12v rails. I figured having two rails would be a benefit to my 6800gpu. Sadly though, one rail supplies the standard 4-pin molexes, and the other rail powers the 4-pin P4 connector. Well damnit anyway, I run with AMD!! SO the alternate rail seems unuseable, due to mobo's lack of P4 connector.

I pried a female connector off a dead P4 mobo, thinking I could fashion something, but then felt I better research a little. I could not find anyone even contemplating the issue - likely due to the lack of dual rail PSU's I guess. Anyone know why I should NOT try to build something to make use of that rail?

thx for any ideas -bios

 

[Glavinsolo]

yes, leave it alone and when you upgrade to skt. 939 it will be useful. I have an enermax 430watt with 2 12v rails. And everything is rock solid. Just tie it back and wait for an upgrade.

 

[Zepper]

There are plenty of Socket-A mobos out there with the P4 socket for CPU power. For the most part, I won't buy one without it any more. All of them SHOULD have the P4 connector as AMD has recommended powering thier CPUs off the 12V rail at least since the Athlon was introduced.
. So sell your mobo and get one with the connector... I've moved 3 or 4 socket A mobos thru ebay and elsewhere in the last month or so, so I guess there is still a good market for them.
.bh.

 

[Biosylum]

The 12v1 rail runs power to the mainboard, which gives the AGP bus power, which vid card does use. So cards do get partial power from the 12v1 rail. But new cards also require power through a molex connector (sometimes two seperate molex lines). So cards genrally get power from both rails, on dual rail PSU's - but I want to keep my card on just one rail (if only for the sake of accomplishing the task). I guess I would need to find out for sure if the card pulls any power from the +5 line on the molex connector - before trying to make an adapter to run from the P4 4-pin connector to a regular molex.

It would seem like a safe mod - due to the fact that on single rail PSU's, that +12v rail supplys all the connectors, including the P4 connector. Even if I get a different AMD mobo with the 4-pin connector, I would still have to connect a molex from the 12v2 rail to the vid card, and that is what I want to avoid....

why?? because it seems like a safe, plausible course of action. Why waste that stable 12v rail, and dump everything else onto the second rail? (which has less amps BTW).

Somebody think about this for a moment. I could have gotten a decent PSU with 30A (give/take) on main rail, and I would feel safe putting my videocard on there with everything else - but I didn't, I went with dual, which I find I can't fully use

I see that P4 connector just dangling there with harvestable power, but it seems no one has ever thought about trying this idea before.


bummer

 

[Zepper]

Well, you can make an adapter for the P4-12V lead... those 4-pin square shells and contacts aren't too hard to find. Or you could just splice right onto the wires. Easy to do with 3M inline splicer/couplers.

.bh.

 

[VirtualLarry]

Originally posted by: Biosylum
Somebody think about this for a moment. I could have gotten a decent PSU with 30A (give/take) on main rail, and I would feel safe putting my videocard on there with everything else - but I didn't, I went with dual, which I find I can't fully use I see that P4 connector just dangling there with harvestable power, but it seems no one has ever thought about trying this idea before.

Hmm, that's a really good idea for a mod, and a really good point about the dual-rail vs. single-rail 12V PSUs. Mine is an older "P4 ready" 350W PSU, with a P4 12v connector, but as far as I am aware, it's still a single-rail 12v supply. I could see how, on dual-rail supplies, they might design it to "apportion" power to each rail, and if one was underutilized, it might simply have been better to go with a single-rail design in the first place. (I blame Intel.)

Anyways, seeing as how many modern video-cards require a seperate dedicated molex, and some recommend two, using a seperate 12V rail connector coming off of a dual-rail PSU would be advantagous.

You're right though, I have no idea if the video cards are currently designed to also take 5V power from those molexes as well.

Power-distribution and regulation in the PC needs a major overhaul, it seems. Everything needs dedicated plugs/wires from the PSU now, and yet still every single device seems to have a multitude of regulators and voltage/signal-level converters, like video cards, motherboards, and who knows what else. I mean, it mostly works, but it just seems somehow a bit in-efficient in some ways. The rapid bifurication of PSU and device power-connector and supply-requirement standards is causing quite a bit of integration and purchasing hassle for the customer too.

 

[Biosylum]

I really can't believe I'd be the first to apply this line of thinking, but I've found no reference to this mod idea. My videocard does use the +5v line, so I will remove the +/- line for 5v from a molex, and place it in a new, empty molex. Then pull one set of -/+12v lines from the P4 connector, and place them in the new molex. Then plug that baby into my videocards female molex. I think it will be great.

From reading pdf link below, I now realize that what I will actually have is power from the AGP bus coming from the 12v1 line, coming through the main power connector, and power from the 12v2 line, coming through the adapter I plan to fashion. So my plan ends up being backwards. I wanted the card on a separate rail completely;it will now be on both rails - but, it will be the only thing tied into the 12v2 rail (so far).

I may hold out a little while to see if others chime in with fear, or support. Sure, I could buy another mobo that would basically do a similar thing, but this mod should be a couple bucks tops. -bios

http://www.formfactors.org/develope...%20Ratified.pdf