PSU SLi complient?

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   I know nothing of SLi configurations.

    I have an old, but good PSU which was manufactured before the age of
SLi graphic cards. I am considering purchasing a ASUS M2N SLi Deluxe or
the ASUS M2N32 Deluxe motherboard, which would entail purchasing a PCI-E
graphics card (updating my AGP card).

Because I am only interested in photo editing etc, and not high end
definition games, and would only anticipate using one graphics card
installed in my pc. Would my old PSU suffice? or is there a connection
on the card which my PSU will not be able to use?

   Thanks !!! in anticipation of your replies.

Re: PSU SLi complient?

brother wrote:
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Fortunately, you gave absolutely no info about the old supply.

1) Can a 20 pin power supply be used with a 24 pin motherboard

    Yes, if there is only one video card in use.

2) Do I need a 2x2 square ATX12V connector ?

    Yes. The supply must have one of those, because it will be
    powering the processor on any new motherboards. The proper
    connector will have two yellow wires and two black wires.

3) Are there any other weird connectors ?

    Molex 1x4 (traditional EIDE drive power).
    SATA power (used on SATA drives that have the new style connector)
    Floppy (same as before, small 1x4)
    PCI Express 2x3 (used as auxiliary power, on higher power video cards)
    PCI Express 2x4 (same as a 2x3, only one extra pin is used for presence

    Adapters are available for some of them.

4) What really matters in the ratings printed on the side of the supply ?

    Everything :-)

    Each output rail has "volts @ amps". If you draw more than the
    rated amps, part of the power supply overheats and it shuts off,
    or you trip the overcurrent, if you draw a lot of current.

    Rails also have separate or combined power ratings, and those
    can be imposed by thermal conditions inside the supply. The 3.3 and
    5V could share some circuitry, limiting the total power drawn fro
    both at the same time. If the supply has more than one 12V rail,
    the combination of several 12V rails can be limited as well.

    The overall supply has a power limit, but it is very difficult to
    exceed that limit. You would exceed the individual limits of the
    separate rails, before approaching the overall power limit. Only
    a controlled load, from a power supply tester, could control the
    test conditions well enough, to properly test at the max overall power
    rating. Computers tend to load one rail more than the others, so
    load things kinda "lopsided".

To work an example, in very skimpy detail.

    Processor   - 65W (mentioned in the adverts for at least some of the
    Motherboard - 50W (includes motherboard and RAM, and this number is a guess)
    Video card  - 35W (for an entry to lower-mid range card)
    Hard drive  - 12W
    CD/DVD      - 25W (an overestimate, but printed in some spec sheets.
                       They draw much less power when no media is present)
    Fans        -  6W (for basic fans)
    Standby PWR -  5W (+5VSB for LAN chip and keeping RAM refreshed in standby
                       or maybe even for some USB functions)

    Total       - 198W

Modern computer builds, tend to put more of their load on the 12V rails.
Older computers loaded up the 5V rail. So some of the older supplies would
have a 5V @ 35A output, and maybe a lot less for 12V. Tne newer supplies have
generous 12V ratings.

Post the numbers on the side of the supply, to give some idea as to what
your old supply is capable of. This picture is an example of a label on
a power supply.

Notice that the sum of all (voltage * current) is way more than the
total power (350W in that picture). It means that an individual rail
can be more heavily loaded. That particular supply would be suited for
use as a replacement on an old computer (one that needed lots of +5V),
and the supply can also work with new computers that like to use +12V.

In terms of the 12V rail

1) 65W processor - 65W/12V * (1/0.90) = 6.02A. That is the current drawn from
    the ATX12V 2x2 square connector, which is a 12V load. The 0.90 number
    represents the 90% conversion efficiency of the Vcore regulator (coils,
    caps, mosfets near the CPU socket).

2) Video cards - PCI Express likes to use the 12V rail. For practical purposes,
    we could say a 36W video card uses 12V @ 3A, in round figures. The cards
    also have a 3.3V rail, but it is lightly loaded.

3) Hard drive - 12V @ 0.6A while sitting in the desktop. Uses up to 2.5A for
    the first 10 seconds of operation (spinup). Also uses some 5V power.

4) CDROM drive - I've measured 12V @ 1.0 amp while the media is spinning at
    max speed.

5) Fans - the rating is frequently on the fan label. 12V @ 0.5A might be enough
    for three weak fans.

Examples of some modern video cards and their power numbers:

If you really want this question answered, provide a hardware inventory of
the parts in the new computer, plus copy all the numbers off the label
on the side of your current power supply. It really depends on the 12V rating
of the old supply, as to whether it is a candidate or not. If you had
12V @ 15A, for example, that is a good minimum number for a supply you
want to reuse. Such a supply might be good enough for the computer
outlined in the "skimpy detail" section above.


Re: PSU SLi complient?

brother wrote:

   Sorry, I forgot to mention; my PSU is the
TAGAN 480W TG480-U01
It's specifications can be found here:

Re: PSU SLi complient?

brother wrote:
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TAGAN 480W TG480-U01

+3.3V @ 28A, +5V @ 48A, +12V @ 28A,
-12V @ 1A, -5V @ 0.8A, +5VSB @ 2.5A
3.3/5V combined    < 240W
3.3/5/12V combined < 460W
total              < 480W

That is plenty of supply. You can even have
a decent video card (for gaming) if you wanted.
But for Photoshop, a 35W video card is fine.

The only thing you might need at some future
date, is an adapter to go from a couple
Molex connectors, to make a PCI Express 2x3
connector. But only if your video card happens
to need it. A 35W video card should not need a
connector on the end - this is an example of a
PCI Express without power on the end.

This is an example of a card with a PCI Express 2x3 on the end.

The Molex to PCI Express 2x3 cable on the right here, is an adapter
included with the video card in the last picture. The two dongles in
the middle of this picture, are adapters for converting from DVI-I to
VGA (15 pin traditional video card connector).


Re: PSU SLi complient?

Paul wrote:
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Thanks Paul !
Everything is clearer to me now. I didn't now about the connectors on
the PCI-E cards.

Re: PSU SLi complient?

On Tue, 06 Nov 2007 21:53:36 +0000, brother

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Knowing more about it might be really important (or might
not, keep reading).

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What's "etc" mean?  Photo editing needs nothing special,
even integrated (lowest end) video would suffice, as-in, be
100% functional only having slightly lower memory bandwidth.

Quoted text here. Click to load it

Whether your present PSU is capable of the new system has
little to nothing to do with your video card "needs", only
which card you choose, since you don't need nor would
benefit from a higher-end card optimized for gaming and as
such, uses more power towards that end.

Generally speaking, we'd need to know brand, model, 12V
current rating of your present PSU, and a list of all the
currently anticipated components in the new built.  A ball
park number for a new system would be to have at least 18A
on 12V rail if a single rail PSU, or at least ~28A if a
pseudo-split rail design.

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