At-p4 Psu ????

[Junk Parts]

Since its raining its ass of today I just may bolt together a PC. My question is, can I use a P4 PSU on a Gigabyte GA-5AX Mini ATX motherboard? I would plug in just the big molex plug and leave the four wire 12 volt plug dandle. I do have a little compaq AT PSU but its rivited into the cheap compaq case.

[kc8adu]

Re: At-p4 Psu ????

yes.

[ratdude747]

Re: At-p4 Psu ????

thats perfectly ok, thats what they are designed to do.

[washu]

Re: At-p4 Psu ????

It's fine most of the time, but not always. An ATX12V 2.0 power supply might not have a enough 5 V / 3.3 V current for an older board. Newer power supplies have more 12 V current and less 5 V / 3.3V current. For example an old 350 W I have supplies 230 W combined 5 V / 3.3 V. My new 350 W supplies only 130 W for those two. A high end Athlon with a power hungry video card could easily go over that 130 W.

Your SS7 board should be fine with anything, it's not going to draw that much power.

See: http://en.wikipedia.org/wiki/ATX#Int...old.2Fnew_PSUs

[Junk Parts]

Re: At-p4 Psu ????

Well the CPU will be an old AMD 533mhz. The video card will be a little 4 meg ATI AGP. It will also have just one DVD Drive, and no floppy drive.

[washu]

Re: At-p4 Psu ????

The max TDP of the K6-2 is only 25 W so you'll be fine with pretty much anything. Just check the max 5 V / 3.3 V wattage on the power supply to be sure. Unless it below about 50 W you'll be fine.

[acstech]

Re: At-p4 Psu ????

Keep in mind though, that most cheaper PSU's are group regulated, so you could end up with high +12v or low +5v. Check it with a voltmeter.

[Junk Parts]

Re: At-p4 Psu ????

Well I got side tracked with this dang Lappy and pulling/packing parts for RatDude. I think that I'm sending him enough good stuff to build a nice little fast AMD PC if he has a case for it. Didn't get around to doing anything with the olde time AMD 533 build as of yet. The PSU I'm going to use is a Future Power with a claim of 400 watts output. I have a RaidMax 450 around here someplace too. I know, they are all junk but they will work for now.

[ratdude747]

Re: At-p4 Psu ????

i have a case... but i thought all i was getting was a cpu and ram? i have a socket a board with a 2400 t-bred in it...

[Junk Parts]

Re: At-p4 Psu ????

I'm sending some stuff. If you don't need it trade it off or put it in the trash bin. Still side tracked with this Lappy. Its making me mental again....

[larrymoencurly]

Re: At-p4 Psu ????

Is the square 4-pin +12V connector on the mobo even connected to the single yellow +12V wire on the 20-pin connector? Because the mobos I've checked kept the +12V power for each connector separate from one another (the +12V wire on the 20-pin connector powered the PCI slots, the +12V from the 4-pin connector powered the CPU), and the mobo wouldn't boot without the cable plugged into that connector. I've seen only one mobo that powered the CPU from the +12V wire of the 20-pin connector -- a BioStar Socket A that didn't even have the other connector.

[washu]

Re: At-p4 Psu ????

larrymoencurly: Unless the power supply really has two 12 rails, the 4-pin +12V is connected to the +12V wire on the 20-pin connector internally. The power supplies with the 4-pin have beefier +12V sections, but usually it's the same regulators for both.

On motherboards that don't have the 4-pin the CPU VRMs run off the 3.3 V or 5 V. That's why some newer power supplies with weak 5 V / 3.3 V sections can get overloaded on socket A boards. The +12V on the 20-pin is just for the PCI / AGP slots. If that BioStar was really running the CPU off the 20-pin +12V it was breaking the ATX power specs.

[larrymoencurly]

Re: At-p4 Psu ????

But even a single-rail PSU connects the +12V on the 20-pin socket to the +12V on the 4-pin socket, with most mobos the CPU VRM still gets power only from the +12V of the 4-pin connector. I think I've proved this by forgetting to plug in the 4-pin connector.

I put a clamp-on ammeter on the power wires to the BioStar, and the current measurements for the +5V and +12V were very different than those taken earlier of my ECS K7VTA3 ver. 8 when it ran the very same CPU (the BioStar was its replacement), and the K7VTA3 definitely used +5.0V for the CPU VRM. That BioStar was a wierd mobo.

[washu]

Re: At-p4 Psu ????

larrymoencurly: I think we are in agreement, just saying the same thing differently. The two +12V lines are connected inside the power supply (unless it's a real dual rail) but they are usually not connected on the motherboard. The 20 pin will not supply +12V to circuits expecting it from the 4 pin.

The 20 pin connector is only rated for 72 watts of +12V. An athlon with a few cards can easily go over that. That BioStar was defianly not compliant with the ATX spec.