ATX power supply, 20 vs 24 pin

  • Thread starter Thread starter Dale Pontius
  • Start date Start date
D

Dale Pontius

The AT supply for my Tyan Trinity (Still on a K6-3 like Kieth was, until
recently) failed recently. I decided to try using an ATX supply I had,
but it won't fit gracefully into the box, as the interior fan is on TOP,
and it's a little flakey, and won't start up every time.

I have another ATX supply, and actually ended up using it in a machine
at work for several months when I thought its power supply was acting
up. (The real problem was more sinister, and the machine is now
considered dead, though I still have it in my office.) By the way, that
machine is/was a 600MHz Pentium III, Micron Millenium.

But until I tried to plug that supply into my Trinity, I hadn't noticed
that it had 24 pins. The keying is such that it would plug in to the
Trinity's 20 pin connector, but there's a capacitor there that won't
physically permit it to fully seat.

I've thought about taking my Dremel and cutting the extra 4 pins off.
But before doing that I want to be sure I'm not about to do something
bad to the Trinity because even though keyed alike, the connectors may
not be truly 'superset compatible'. This fear is heightened by the fact
that the colors of the wires on the two connectors are in NO way
matching. I've looked for such things on the web, and found 24 and 20
pin diagrams that look like the superset I need. But the colors on that
diagram are nothing like what's heading into this connector.

But this thing simply plugged into a 2000-era ATX board and simply
worked.

So did somebody bork the wire colors, or is it really a different
standard which I haven't found, yet?

So how much load do I need to put on which pins/voltages, so I can power
the thing up in isolation and check the voltages, pin by pin?

Thanks,
Dale Pontius
(My wife and I are using the kids' computer for the moment, but we need
to get our own back before our son heads off to college.)
 
But until I tried to plug that supply into my Trinity, I hadn't noticed
that it had 24 pins. The keying is such that it would plug in to the
Trinity's 20 pin connector, but there's a capacitor there that won't
physically permit it to fully seat.

So did somebody bork the wire colors, or is it really a different
standard which I haven't found, yet?
Click to expand...

It's a different standard (EPS12V). 24-pin sockets are typically
used on server-class motherboards.

If you don't mind spending money, there are companies which market
24-pin to 20-pin adapter cables. Go Google. [Though one vendor I
ordered my adapter cable from had the male and female plugs mixed
up - and couldn't understand when I explained their mistake. I
eventually gave up - got the cable I wanted from another vendor.]

mikus
 
... I hadn't noticed that it had 24 pins.

Sounds like an EPS-12V supply, and
probably an EPS-12V version 1.7 at that.
So did somebody bork the wire colors,
or is it really a different
standard which I haven't found, yet?
Click to expand...

And if you buy a new one, it's likely
to be EPS-12V version 2.0.

They changed the connector at 2.0, and
I'm not sure if there are backward-
compatibility concerns.

You can find the 2.0 spec at:
http://www.ssiforum.org/docs/EPS12V_Spec_2_11.pdf

Hmmm. Based on the filename, it appears that
they've tweaked it again.

--
Regards, PO Box 248
Bob Niland Enterprise
mailto:[email protected] Kansas USA
which, due to spam, is: 67441-0248
email4rjn AT yahoo DOT com
http://www.access-one.com/rjn

Unless otherwise specifically stated, expressing
personal opinions and NOT speaking for any
employer, client or Internet Service Provider.
 
As far as I'm aware, it looks like the same pinout effectively. The
EPS requirement demands dual output for the +12V but shouldn't be a
problem if the board only expects to have single +12V from the PSU.


--
L.Angel: I'm looking for web design work.
If you need basic to med complexity webpages at affordable rates, email me :)
Standard HTML, SHTML, MySQL + PHP or ASP, Javascript.
If you really want, FrontPage & DreamWeaver too.
But keep in mind you pay extra bandwidth for their bloated code
 
You can find the 2.0 spec at:
http://www.ssiforum.org/docs/EPS12V_Spec_2_11.pdf
Click to expand...

404

Looks like they fragmented the spec and
moved the bits to:
http://www.ssiforum.org/specifications.aspx[/QUOTE]

Thanks for the pointer. For little more than the cost of the silly
adapter, I think I'll just buy an ATX power supply. I may still
look at your document and see if the pins are a correct subset. I
also need to look at the system at work and see if the colors are
so odd. (5 red or black (forget which, or both?) wires in a row
on one side.)

Dale Pontius
 
Dale said:
404

Looks like they fragmented the spec and
moved the bits to:
http://www.ssiforum.org/specifications.aspx
Click to expand...

Thanks for the pointer. For little more than the cost of the silly
adapter, I think I'll just buy an ATX power supply. I may still
look at your document and see if the pins are a correct subset. I
also need to look at the system at work and see if the colors are
so odd. (5 red or black (forget which, or both?) wires in a row
on one side.)

Dale Pontius[/QUOTE]

1->1
2->2
3->3
4->4
5->5
6->6
7->7
8->8
9->9
10->10
13->11
14->12
15->13
16->14
17->15
18->16
19->17
20->18
21->19
22->20

There are also an 8 plug instead of the 4 plug:
1->1
2->2
5->3
6->4
 
1->1
2->2
3->3
4->4
5->5
6->6
7->7
8->8
9->9
10->10
13->11
14->12
15->13
16->14
17->15
18->16
19->17
20->18
21->19
22->20
Click to expand...

Just to be clear, is this mapping:

ATX12V => EPS12V

1 11 => 1 13
2 12 => 2 14
3 13 => 3 15
4 14 => 4 16
5 15 => 5 17
6 16 => 6 18
7 17 => 7 19
8 18 => 8 20
9 19 => 9 21
10 20 => 10 22
11 23 ) Last four locations
12 24 ) not used with ATX12V
There are also an 8 plug instead of the 4 plug:
1->1
2->2
5->3
6->4
Click to expand...

....which would be: (?)

ATX12V => EPS12V
1 3 => 1 5
2 4 => 2 6
3 7
4 8

My Tyan S2875 has an EPS12V set of connectors, but my case had an ATX12V
supply, which did surprise me. The instructions said it would work (it
did), but I was a tad leary about plugging in a drive power cable into the
board to get additional power, since the board really wanted all the power
connections of the EPS12V standard.
 
Back
Top