20 vs. 24pin general question

[Zumino Zufeilon]

Ok, looked all over, and nobody seems to explain this in a manner that I can follow. . . . In otherwords, explain it to me like I'm a 2year old monkey

Some of these are really stupid questions, and somehow I seemed to miss this important information and change. Didn't matter a whit until now that I'm spec'ing a puter for a friend, and AMD64 systems are what he wants.

What is the difference between 20pin and 24pin connectors? I know that if I plug in the 20pin it will "probably" work fine for powering a computer from reading posts here.

Why is it I can only find a very limited number of 24pin PS's on the Egg, but I do see a number advertised 20+4? Does that mean the 4pin P4 connecter can be plugged in at the end of the 20pin(probably not, hell, I'm not even going to try that out unless about 10 people say it's fine), or is it just describing a standard 20pin with the 4pin connector?

Does that 4pin do anything on a non-P4 system? Having never build a p4 system, I've no idea if it does anything their either though


puter I'm building is a AMD64 939 Venice 3k, on an ASUS board, with just 1 DVDRW, an 1 HDD(120gig SATA), and a PCI-E 6600GT Vid at the highest power, so I don't think it'd draw a lotta power, but the whole 20/24 pin things got be flummoxed, an I don't like being flummoxed.

P.S. please explain this like I'm someone dumb enough not to already know the answer to that question. I've seen Icewind break out that pretty graph, but I've no real understanding of the variations between the ATX's verisons, so that graph, while full of information, does squat for me. That said, I've a suspicion that this is one of those things that when explained, suddenly I will "get it" and totally understand what's going on, but I seem to not be there yet :/

I really do appreciate the help here, hate asking the really stupid questions, but

 

[dandragonrage]

24-pin is like having the extra 4 pin connector, yes, but it's not the same. The P4 connector can NOT be used for the extra 4 pins.

Get something ATX12V 2.0 complient, preferrably also with an 8-pin EPS connector.

 

[Ice Czar]

cut and paste (buried hither and yon should be the answers )

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depends on the mobo
if it has a 4 pin auxillary connector the +12V
(all P4 and some AMD)
otherwise its drawing off the +3.3\5V rail
(all P3 and some AMD))

http://takaman.jp/D/index.html?english

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
which is both the 24 pin and the 4 pin +12V auxillary and that is likely to increase to 8 pins in the near future as well > http://hardforum.com/showthread.php?t=865804

then there are adapters

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

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[Zumino Zufeilon]

alrighty, belive it or not, that was exactly what I was looking for! I think I got it now, that said, the board in question has the 4pin connector. At the moment, he's trying to save money by reusing as many parts as possible(DVD/Case/PS/etc), but wanted to upgrade the board/proc/vid. The 20+4, while not as good as having the dedicated 24, will still provide the required power, espeically as it will only be a "till he get's a new PS" kinda thing, yes?

Old PS is a 350 Antec Silent Power, new Board is either a MSI or ASUS nForce4 board, running a Venice 3(probably stock, but I might OC a touch, nothing much), an a 6600GT PCI-E16X. Would also have a SATA 120gig, the DVDRW installed, but that's about it.

 

[bobsaget]

I was in the same situation as you just a few weeks ago...

I ended up getting the FSP Blue Storm 500w.


I'm very glad I did.