So, I have an old pentium 3 power supply at 350W that I wanted to install a pentium 4 / newer motherboard on.
Now, there are 3 things to be aware of.
1) The old PSU's often had 20 pin atx and the new motherboards sometimes accept 24 pin atx.
This is often fine, unless you are running a high power PCI / video card; you can just plug in the 20 pin MB and it will run fine.
2) The old PSU's are often optimized for the 5 volt rails (red on the molex connector) rather than the 12 V rails (yellow) which might mean that the power supply may not supply enough power to the right rails even though the watt rating is acceptable.
3) The old PSU's don't have the P4 ATX connector that plugs into the motherboard CPU socket.
You can buy an adapter for this; but being impatient and a cheap bastard; I decided to look around and see what I had.
I found a 2 molex => 6 pin PCIE power adapter that came with my video card around the house.
http://www.amazon.com/HDE-PCI-Expres.../dp/B000IZBIVC
After doing some web research; I found that it is possible to modify this to work as the P4 power connector.
What you have to do
a) The power cables are reversed in PCIE and ATX P4 socket so even though it fits; DO NOT PLUG IT INTO THE MOTHERBOARD WITHOUT MODIFICATION unless you wish to fry your chip.
Instead, you will have to do some molex pin flipping to get the 12 Volt and Ground lines flipped around.
(you can google the pinouts).
http://www.smpspowersupply.com/connectors-pinouts.html
http://www.techpowerup.com/articles/...ocking/psu/116
b) it has been recommended to use 2 molex connectors since the power draw from the P4 sockets on the older P4 (ie: pentium d - 130 Watts max TDP) may exceed the molex 12 volt copper wire amperage and melt the wire if drawn from 1 line alone.
c) Finally, there are 2 extra ground wires that aren't necessary, I just unhooked them from the molex cable.
Since I didn't have molex modification/connector tools; I managed to use a small flat head screwdriver/paperclip to press in the retaining clips on the male and female molex heads respectively.
You can also use industrial staples in place of the molex removal tool (you can google it).
I found the trick was to press in the tabs and use a small hex key to PUSH out the molex connector at the same time as pulling lightly.
The key was to PUSH the connector out since a lot more force could be exerted without worry of snapping/damaging the wire.
I just wanted to add this to the internet knowledge base as I did a fairly thorough search and didn't see much regarding the issue.
Most people have new PSU's or recommend buying a modern PSU in this case.
In my case, I am doing this on a very old Pentium 4 board that is failing anyways and I REALLY didn't want to waste money on it.
In my region, you can get a new case and cheapie PSU for $35 candian on sale.
Having said that, none of us would be on the badcaps forums if we didn't like
tinkering with electronics (and winning
KEYWORDS:
ADD P4 ATX CONNECTOR TO OLD PSU, MODIFY PCIE ADAPTER TO FIT P4 ATX, CPU POWER SOCKET.
Now, there are 3 things to be aware of.
1) The old PSU's often had 20 pin atx and the new motherboards sometimes accept 24 pin atx.
This is often fine, unless you are running a high power PCI / video card; you can just plug in the 20 pin MB and it will run fine.
2) The old PSU's are often optimized for the 5 volt rails (red on the molex connector) rather than the 12 V rails (yellow) which might mean that the power supply may not supply enough power to the right rails even though the watt rating is acceptable.
3) The old PSU's don't have the P4 ATX connector that plugs into the motherboard CPU socket.
You can buy an adapter for this; but being impatient and a cheap bastard; I decided to look around and see what I had.
I found a 2 molex => 6 pin PCIE power adapter that came with my video card around the house.
http://www.amazon.com/HDE-PCI-Expres.../dp/B000IZBIVC
After doing some web research; I found that it is possible to modify this to work as the P4 power connector.
What you have to do
a) The power cables are reversed in PCIE and ATX P4 socket so even though it fits; DO NOT PLUG IT INTO THE MOTHERBOARD WITHOUT MODIFICATION unless you wish to fry your chip.
Instead, you will have to do some molex pin flipping to get the 12 Volt and Ground lines flipped around.
(you can google the pinouts).
http://www.smpspowersupply.com/connectors-pinouts.html
http://www.techpowerup.com/articles/...ocking/psu/116
b) it has been recommended to use 2 molex connectors since the power draw from the P4 sockets on the older P4 (ie: pentium d - 130 Watts max TDP) may exceed the molex 12 volt copper wire amperage and melt the wire if drawn from 1 line alone.
c) Finally, there are 2 extra ground wires that aren't necessary, I just unhooked them from the molex cable.
Since I didn't have molex modification/connector tools; I managed to use a small flat head screwdriver/paperclip to press in the retaining clips on the male and female molex heads respectively.
You can also use industrial staples in place of the molex removal tool (you can google it).
I found the trick was to press in the tabs and use a small hex key to PUSH out the molex connector at the same time as pulling lightly.
The key was to PUSH the connector out since a lot more force could be exerted without worry of snapping/damaging the wire.
I just wanted to add this to the internet knowledge base as I did a fairly thorough search and didn't see much regarding the issue.
Most people have new PSU's or recommend buying a modern PSU in this case.
In my case, I am doing this on a very old Pentium 4 board that is failing anyways and I REALLY didn't want to waste money on it.
In my region, you can get a new case and cheapie PSU for $35 candian on sale.
Having said that, none of us would be on the badcaps forums if we didn't like
tinkering with electronics (and winning
KEYWORDS:
ADD P4 ATX CONNECTOR TO OLD PSU, MODIFY PCIE ADAPTER TO FIT P4 ATX, CPU POWER SOCKET.
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