is it ok to use the non-athlon/p4 psu on a nforce2 board?

[smallghost]

Hi all, I just built a system for a friend of mine. He is using an old power supply (the one with one power plug) other than the new type (two power plugs: one big, one small). He is using an Abit NF7 nforce2 board. Is it safe to run a new AMD system on an old power supply? Thanks in advance.

 

[glock19owner]

As long as the PSU is ATX it won't matter...and the PSU will have to be ATX or they wouldn't be able to hook it up to the MB...

 

[couchpotato]

the Nf7 does not use the 5Volt line
to run the processor. These boards use the 12 Volt line.
All is well and will work --- BUT the single 12 Volt line is carrying
9 Amp. With the second connector plugged in there will
be 3 X 12volt lines - each one only carrying 3 Amp.
I understand the ATX Connector has a running capacity
of 6 Amp per contact - so 9 will be pushing the limit.

I have a Abit N-force2 - and an old PSU. I have a
DC Current Meter and was shocked by the measurements.

On the bright side - if you can wield a soldering iron - the
extra connector can be retro-fitted easily enough.

Bottom line - it will work as a "get by" but I would not
overclock with it.

 

[Toshvan]

Hello,

that's was the question I had in mind. I have an old Meridian Tehnology PSU that had served me well a long time. I is an ATX version 2.01 power supply so it doesn't have an 12v P4 connector like an 2.03 ATX PSU has. My motherboard is Soltek 75FRN2-L and the reading for +12v is around 11.7 but the system has been quite stable with an Athlon T-Bred B 2100+ (1734Mhz) overclocked at 2202Mhz with voltage set at 1.675v from the initial 1.6v. Here's Motherboard monitor report:

| CPU | Case | Socket | Core 0 | Core 1 | +3.3 | +5.00 | +12.00 | -12.00 | -5.00 |
| 42°C | 32°C | 35°C | 1.58 V | 4.08 V | 3.33 V | 5.03 V | 11.73 V | -12.44 V | -4.94 V |

Would improvizing (soldering it directly at the PCB of the PSU or using an adapter, ETC...) an P4 type connector to the motherboard help a bit for the +12v value or add to the stability?

 

[couchpotato]

Hi,
mmmm.
I don't actually know . But - since you are happy
to use soldering irons (i.e you are technical)- a check
of the voltage drop across the 12 Volt line to the ATX
connector will give a good indication of the improvement.
If the voltage difference between a unconnected 12 Volt
HardDrive tail (yellow wire) and the yellow wire on the ATX
connector is 0.2 to 0.3 volts or more - then a large
difference can be made. A second cable should half the
voltage drop, and a three wires should cut it by two thirds
(all calculations as a guess).

Be careful

EDIT : oops - Stability ,,,... if it is perfectly stable now - then
no improvement .

 

[couchpotato]

calculations

Here are the calculations - IF volt drop is 0.3
AND the current carried is 9 Amp.

V=IR
0.3 = 9R
R = 0.3/9 = 0.033333 Ohms

two wires (Rt is resistance total, R1 and R2 the resistance of each wire)
1/Rt = 1/R1 + 1/R2
1/Rt = 1/0.033333 + 1/0.033333
1/Rt = 60
Rt = 1/60
Rt = 0.0166666 Ohms

Voltage across is
V = IR
V = 9 times 0.0166666 Ohms
V = 0.15 Volts

Because of the very small resistances here
Your Milage May Vary

 

[whiteemcee]

i've seen people use psu's that were not amd or p4 recommended and had a lot of problems with them such as their computers randomly shutting down and stuff.. but others have worked just fine.. so i guess its the quality of the psu that really matters

 

[Toshvan]

OK, I've just measured the +12v on an unused molex connector and it's 11.96v while the Motherboard Monitor measured value varies around 11.67v-11.73v. Knowing this and considering couchpotatos advice I'm opting for an additional P4 type connector. My plan is to cut a four cell piece of an ATX connector (from dead PSU). It seems it will fit on the P4 type connector. I don't think I will get a chance to strip an orignal P4 type connector anytime soon...

 

[Toshvan]

I did attach new P4 type connector on my PSU-s PCB and... is seems it helped a little. The readings from board sensors are 11.73v-11.8v instead of 11.67v-11.73v before the mod. It's ok my system is stable so I'm not going to sweat about this one. Just one more question...

couchpotato, If I understand well, by doing this I have unloaded the burden off the only 12v rail on the ATX. The current now flows thru three wires instead of just one. As I understand this is the main benefit? Is this correct?

 

[couchpotato]

Yes - exactly .

I have a Tyan 2460 and the ATX connector has a
tendancy to burn contacts at high currents on the
5 Volt lines . These run at 6 Amp constant - and with
double the cables the voltage drop changed by a
similar value to yours.

That's your first Power Mod - What's next ?

 

[Toshvan]

Well, maybe I will desolder the ATX connector form the motherboard and solder the PSU wires directly on it