Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
"Paul" <nospam@needed.com> wrote in message
news:nospam-0808050315130001@192.168.1.178...
> In article <42f6a96c@dnews.tpgi.com.au>, "Dragoncarer"
> <wee@ihaveabrandspankingnew.computer> wrote:
>
>> Uhm...so I've connected my A8N-SLI up and everything, but the board has a
>> 24-pin power connecter, my PSU has a 20-Pin connecter. I didn't realise
>> all
>> this until I installed the Mobo because, well...I'd never hear it
>> discussed
>> before. Is this going to be a problem? Currently it's running fine and I
>> haven't had any Mobo problems that could be attributed to the PSU.
>>
>> Many thanks.
>
> The 24 pin power connector is the same as the 20 pin connector,
> except there are a few extra power signals on it. The reason
> for this, is the PCI Express card slots can carry more power,
> so the power connector was beefed up a bit.
>
> The most crucial difference is the +12V situation. On the
> 20 pin power connector, there is only one wire carrying +12V. It
> powers anything on the motherboard that needs +12V (except the
> processor, and it uses the separate 2x2 power connector). If you
> were using more than one PCI Express plugin card, and they
> drew a lot of current, you could overload the single pin.
> A pin on the 20 pin ATX power connector can safely carry 6 amps
> without serious overheating, so that is the limit for one pin.
>
> On the 24 pin connector, they added a second +12V pin, which means
> the connector can carry up to 12 amps total current.
>
> If the only PCI Express card being used is a single video card,
> chances are the loading on the single pin is within the
> 6 amp limit, so there should be no harm. The A8N-SLI has
> the EZ-Plug connector as well, and if you use that connector
> in addition to the 20 pin power connector, that virtually guarantees
> there won't be a problem. The EZ-Plug (disk drive) connectors
> are rated at 8 amps carrying capacity, so using EZ-Plug plus
> the 20 pin power connector makes room for 6+8=14 amps, which
> is enough for two video cards.
>
> There are two concepts at work here. One concept is the amount
> of current the power supply has to offer (that limit is printed
> on the label on the side of the power supply). The current has to
> flow through some number of connector pins, and both the pins
> and wires have current limits (if exceeded, the metal gets hot
> and the plastic can melt). The numbers I've mentioned above,
> are the safe operating limits for the pins on the 20 pin ATX
> power connector, and for the disk drive connector plugged into
> EZ-Plug. Using the EZ-Plug is a good form of insurance, and
> can be used with one or two video cards (it is not restricted
> to running two video cards).
>
> Now, this topic is a bit more obscure, but I'll mention it
> for the sake of completeness. This article mentions the
> splitting of the +12V rails on some of the high end power
> supplies.
>
>
http://www.madshrimps.be/?action=getarticle&number=2&artpage=1334&articID=332
>
> Older ATX power supplies have exactly one +12V circuit. Some
> of the 500W+ power supplies can have +12V@34A or more as outputs.
> There are no issues with using a supply like this, because all
> +12V power comes from the same circuit. There is no wasted
> capacity, as the 34A can be used by any load. (Splitting
> the output means, if one output doesn't use all its juice,
> the other output cannot gain access to it.)
>
> On the newer 24 pin power supplies, there are two outputs -
> 12V1 (processor 2x2 connector) and 12V2 (everything else).
> A supply like this is OK to use with EZ-Plug on your board,
> because the 24 pin ATX power connector, and its two 12V wires,
> run from 12V2, as do the disk drive connectors. Plugging in
> the EZ-Plug won't harm anything in this case.
>
> There are supplies that have three or four +12V regulator circuits
> in the power supply. According to the madshrimps.be review above,
> the power rails split like:
>
> (Common Plane System) (Split Plane System)
> 12V1 Processors 12V1 Processor 1
> 12V2 Processor 2
> 12V2 Motherboard 12V3 Motherboard
> 12V3 Disk drive plugs 12V4 Disk drive plugs
>
> I would be careful with supplies like this. If you plug in the
> 24 pin power plug, the two 12V wires run on a different 12V output
> than the disk drive plugs. Plugging in the EZ-Plug in this case,
> connects say, 12V2 to 12V3. If the power supply is not designed
> for this, current will flow from one 12V circuit to the other,
> which is not desirable. Note that the A8N-SLI is not listed
> on the web page below, and I'm not sure if the reason is because
> of this 12V issue or not. At the very least, if buying a supply
> with three or more +12V output circuits, I would want to ask the
> power supply maker whether using it on the A8N-SLI is a wise idea.
> You cannot connect outputs on a supply together, unless there is
> provision in the power supply design for current sharing.
>
>
http://www.pcpowercooling.com/products/power_supplies/dual_cpu_selector/?show=T85SSI
>
> The safest course of action, when shopping for a 24 pin power
> supply, is to stick with the common 12V1/12V2 type supplies.
> At the bottom of this web page, is a short list of "certified"
> SLI power supplies, and I would find a supply with one or two
> 12V output circuits. The Turbocool 510 SLI has one 12V output,
> and would be a reasonable solution. The Enermax EG701AX has two
> 12V outputs, and would also look to be safe as a choice. So
> far, it looks like the Turbocool 850 is the only one I would
> not want to use with an Asus EZ-Plug type motherboard. (And
> at the price they are charging for the 850, I doubt anyone
> will be buying it anyway. The design is still impressive, having
> all that power, and only using a single cooling fan.) While
> the EZ-Plug concept can improve the quality of power delivered
> to the video cards, the same objective can be met by locating
> the 24 pin power connector close to the video cards, and a
> motherboard design without EZ-Plug won't have this issue with
> shorting 12V2 to 12V3 etc.
>
>
http://www.slizone.com/object/slizone_build.html
>
> HTH,
> Paul
Phew, lot's of information! But, this was helpful. At the moment, I don't
even have one PCI-E card...but I eventually plan on getting one. I'm even
considering waiting and getting a 7800 or 7800GT...which means I'll only
have one card for avery long time. As you say, the EZ Plug will ensure I
have safe amount of power if I ever were to connect another card.
Thanks heaps Paul.
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