6pin AT Cable?

[-zax-]

Don't know if this has been covered in the PSU section of [H] before, but I did a search and couldn't find anything.

Anyway, I'm sleeving a PSU of mine and making the cables custom lengths to my needs. Also making detachable cables so I can keep the case clean from hanging cables. My question is:

Is there any reason to KEEP the 6pin AT connector on any PSU these days? Besides for a Dell or something that requires it... This will sound dumb as well... but it will not affect my PSU if I do get rid of it ... or will cutting off that AT connector FUBAR my PSU?

I have not had to use this power connector on any power supply I own for quite some time... and would just rather cut it off inside the PSU so I don't have extra cables hanging around.

 

[Ice Czar]

get rid of it
just isolate those ends so they dont ground out

 

[larrymoencurly]

Don't just cut the wires; cover each one's end with at least 1.5" of heatshrink so the little whisker strands can't short something.

Why does it matter if a cable is dangling? After all it's not like it can be seen outside any properly made case.

 

[SockMan!]

What is that cable used for anyway? It seems that just about every power supply has one, but I've never actually seen any situation where it was used.

 

[Ice Czar]

Power supplies become increasingly expensive

When I initially asked about this on a mailing list, Solaris x86 advocate Al Hopper told me I was drowning in my tea, and that it was "all very simple". I love the simplicity of Unix people.

He explained that the later P4 CPUs take their power from a 12 Volt feed and, using the onboard voltage regulators, generate the high current, low-voltages they need to operate (anywhere from ~ 1.6V to around 2.7V). So the first requirement is a PSU that has plenty of power available from the 12V supply. Since the older ATX compatible PSUs didn't supply much current from the 12V section you have to ensure that your new PS delivers enough current (or power in Watts) from the 12V section. That's why using your old P3 ATX PS is a big "no-no".

He then described the history of the post-P3 power supply mess:

The earlier Athlon motherboard manufacturers decided to solve the 12v problem by using an additional 4-pin square connector to get the extra 12V those CPUs required. However many older PSUs didn't provide the 12V 4-pin square connector.

The motherboard makers then wised up and decided that there was nothing magical about a square 4-pin connector, so they put a normal hard disk type socket on the motherboard and provided the 12v power via a standard hard disk (4-pin inline) connector. Problem solved - you may now use your older PSUs provided they supply sufficient 12V current (many did not).

Further confusion came from PSU manufacturers not specifying the capabilities of the PSU in a way that allowed the end user to verify it's 12V power output rating.

In the meantime the ATX spec was saying "use the new 6-pin" inline connector - and very few motherboard makers implemented it.

Just to be sure, some motherboard makers, implemented *both* the hard disk style 4-pin inline connector and the square 4-pin connector. They said "use either or both in any combination you like".

The spec then evolved to the 24-pin main connector. Again, most motherboard manufacturers did not wish to make their customers mad by mandating that they replace their power supplies. This might cause their customers to avoid motherboard upgrades. Some used a "special" 24-pin connector with the extra 4-pin connection blocked off, or colored so that the user could plugin a 20-pin plug into the correct end of the 24-pin socket on the motherboard. Many others simply ignored the 24-pin requirement in the specs. Again - problem solved - use your older PSU.

which is how we arrived at the point of mass confusion we are currently at

the adapters themselves add a little resistance
not completely insubstantial, this applies in either direction

see > http://www.pcper.com/article.php?aid=106

but the reason boards blow and PSUs fry has more to do with trying to power too great a load off a supply simply not up to it
than the added resistance or amps being drawn for 2 pins through one wire

ATX12V v2.0 added the 24 pin connector previously used by EPS12V supplies
but more importantly it allocated more capacity to the +12V rails within each wattage class at the expense of the +3.3V & +5V rails
it also split the +12V rail to isolate fluctuations induced by drives and other components from the CPU on the other rail (not a big deal in a really well regulated supply)
see CPUs used to be powered off the +3.3\5V rail and now they are on the +12V rail
throw in more amps needed by AGP cards on the +12V and even more for PCI-E
and you get the idea

well that standard wasnt widely adopted, as the mobo manufacturers didnt want to force people to buy PSUs, they thought it was a sales disadvantage, yet at the same time the components needed more amps on the +12V rails

thus ATX12V v1.3 supplies started to become hybrids, switching some of the capacity off the +3.3V and +5V rails and onto the +12V rail, yet retaining the 20 pin connector

so its more about the amps for your config than the adapter itself which will determine the risk of employing a 20 to 24 pin adapter
if you have an old school ATX12V v1.3 dont even consider it
if you have a hybrid work the numbers but still give serious consideration to an upgrade

simple example
400Watt supply w\ 18A on the +12V (12x18=216Watts @ 25C derated to say 144Watts @ 40C) with the rest of the capacity (@25C) largely unused on the other rails now only powering memory, some PCI cards, keyboard mouse, maybe AGP but massively under employed

here is another good example
the Antec Phantom is a modern 350 Watt supply
and has 34A on the +12V rails since that actually adds up to 408 Watts
it raises the issue of crossloading

which I'll let Oleg Artamonov explain
http://www.xbitlabs.com/articles/other/display/psu-methodology_13.html

so in the event you actually have an old board its even more fun

well no 4 pin +12V auxillary mobo connector
so your powering the CPU \ mobo off the +3.3V \ +5V rail
http://www.asus.com/products/mb/socketa/a7v8x-mx/overview.htm#

Id assume the Integrated VIA UniChrome Graphics consumes something over the basic mobo spec. the Ti4600 is a wild guess
assumed the worse on the NIC and RAID from the available options
though you could look those up


in this case the +12V rail is largely unimportant
provided it can meet the spinup draw (peak rating)
http://takaman.jp/D/?M=PaQJQbd@bSAgXKk@lWbXgZAZavXCMZ&english

+3.3V @ 12.6
+5V @ 28.5
maximum combined draw of 185W

+12V @ 11A
total 325W


the fsp
http://www.home2000.net/client/fspgroupusacom/proddetail.asp?linenumber=3
http://www.home2000.net/client/fspgroupusacom/images/FSP350-60PN_S.pdf

note the max and "typical" figures no real crossload info is given
(please read that link pages 13 > 16 )

doesnt meet that requirement per se as its an ATX12V v1.3 hybrid Id gather
note that the older models even in a lower wattage class have higher numbers
but they dont list the combined capacity of the +3.3V and +5V rails


nor does the Antec
http://www.antec-inc.com/specs/true380_spe.html

actually using Takamans search feature
brings up alot more info

personally Id narrow the power consumption by researching the RAID and NIC power draw
that should be published info, and the onboard video if you can
then hunt for supplies with the combined capacity on the +3.3V\+5V employing Takaman's search feature, looking for some healthy over capacity to account for an unknown temperature derating curve

your in a bit of a quandry, because what you really want is an old school ATX12V v1.2 or v1.3

Chart by Xbit \ Oleg Artamonov

that hasnt had any +3.3V\+5V amps robbed to pump up the +12V rail like you get in an ATX12V v1.3 hybrid
which for all effective purposes is the V2.0 above
so a little more homework will likely save you some $$ and peace of mind
if you look at the chart wattage, your sitting in the peak of the green box