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Thread: Dual M1-ATX - viable solution to 180W???

  1. #1
    MySQL Error Scouse Monkey's Avatar
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    Lightbulb Dual M1-ATX - viable solution to 180W???

    I was just reading a review of the M1-ATX and went to look at the specs and stuff on the mp3car.com shop (i love it when loads of info and specs and manuals are available as i like to know everything about stuff i buy). and i was wondering if it would be viable to run 2 of these PSUs as one can be set-up as a plain DC-DC or a mixture as it has 8 start/shutdown options...

    I would use both PSUs so they come on when the ign comes on but then have psu 2 also connected to a relay powered by one of the PSU1 molex outputs so it will only shutdown after PSU1.

    PSU1 would power the mobo and CPU and ram etc while PSU2 would be powering the HDD, DVD, USB devices (splicing into the power or using a hub).

    with this setup PSU2 (peripherals) would always be on when PSU1 is on and stay on slightly after to prevent hardware problems for hibernation etc.

    I am looking at powering a microATX with athlon XP-M and 1stick of DDR off off 1 90W psu - anyone think it will be ok? power calc says i need 110W but that is with a separate car dbut i would be using the on board so don't know how much power to assign for the mobo with video and sound.

    For reference:

    from Opus manual: (max not peak specs)
    3.3V 10A
    5V 10A
    12V 5A
    -12V 0.2A
    5V standby 1A
    Input 7-18V

    From M1-ATX specs: (max not peak)
    3.3V 10A
    5V 10A
    12V 2A
    -12V 0.15A
    5V standby 1.5A
    Input 5.7-30V (8V startup min)

    This would give us a potential 180W for about $150 (less than a $1 a watt) with isolated power for the mobo and cpu to protect them from the drives heavy drive consumption.

    Also what are the typical 12V requirements for a mATX board? would splicing the second PSU into the ATX 12V help if you are not suing it for anything else (ie no 3.5 inch drive).

    Andy

    EDIT: you could also just leave PSU1 on for standby as you don't knee the peripherals on. and could jsut set a longer off delay on PSU2 to simplify things.

  2. #2
    FLAC
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    Your cpu alone probably needs 4*to 5A on the 12V line (since it's an m-Atx board) even with the Mobile Athlon.
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  3. #3
    MySQL Error Scouse Monkey's Avatar
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    Quote Originally Posted by Arathranar
    Your cpu alone probably needs 4*to 5A on the 12V line (since it's an m-Atx board) even with the Mobile Athlon.
    bugger!

    Well that answers that then - i had no idea what kind of in power a board needs on 12V.

    Why does the cpu run off the 12V if they only run at 1.5-3.3V?????

  4. #4
    Maximum Bitrate EBFoxbat's Avatar
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    Quote Originally Posted by Arathranar
    Your cpu alone probably needs 4*to 5A on the 12V line (since it's an m-Atx board) even with the Mobile Athlon.
    Maybe not. What board is it?

    I'm thinking about using two to power an linux-xbox.
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    MySQL Error Scouse Monkey's Avatar
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    Am gonna use an nforce2 mATX - have 6 i am looking at. CPU will be 45W so will need 4A. Probably best going for a sproggy 4.5 in that case! Just pricing up the components in the UK but it looks like it is cheaper and easier to buy the full kit and the difference between semi and full is less than the cost of the chips and that is not including the maxim 788 which i havent found yet.

  6. #6
    MySQL Error MatrixPC's Avatar
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    Not always true that the CPU get its power from 12V. This is depend on the mobo designer. If the mobo has and extra P4 style 4 pin plug, more likely the mobo/cpu need more power on the 12V rail. Otherwise, it will be more on 5V or 3.3V. In my case Asus A7N8X-VM/400 with Mobile CPU, it needs more power on 5V than 12V or 3.3V.

    Some people on PC Perpective did some test.
    http://forums.pcper.com/showthread.p...postid=2493090
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    MySQL Error Scouse Monkey's Avatar
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    That is very interesting and my initial response was "email the mobo makers and ask" but then i read the bit about the Asus tech support and figured as much (they were that much use when i had a problem with a friends board).

    None of the mATX boards i have seen have P4 style connectors.

    there results show pulling a max of 15A on the 5V line - ouch!

    But then againt he CPU they used must be rated at about the 65W thay get on the 5V line so if you make a broad assumption and say nothing else uses any of that then a mobile CPU rated as 45W chould be pulling 9 amps! Just in range but close!

    For me i thinkt he cheapest oprion will be a mas/sproggy 4.5 (about 105 + any import) however Mtrix, yu may be able to answer this for me: what is this auto startup for cold starts about? can it be dissabled. I am pretty sure my PC is never gonna drop below 8V on startup as it is a small car and if the battery starts to show signs of weakness it is out of there before you can say "tank battery".

  8. #8
    FLAC
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    I think all P4 boards have the p4 connector - even then mini-itx ones. My micro ATX Soyo AMD board has one and it won't boot unless it's connected.

    Anyone know where I can get one of those clamp-on ammeters the linked post mentions? I'd love to know exactly what currents my system draws but I didn't want to have to break the wires.
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  9. #9
    MySQL Error MatrixPC's Avatar
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    Quote Originally Posted by Scouse Monkey
    That is very interesting and my initial response was "email the mobo makers and ask" but then i read the bit about the Asus tech support and figured as much (they were that much use when i had a problem with a friends board).

    None of the mATX boards i have seen have P4 style connectors.

    there results show pulling a max of 15A on the 5V line - ouch!

    But then againt he CPU they used must be rated at about the 65W thay get on the 5V line so if you make a broad assumption and say nothing else uses any of that then a mobile CPU rated as 45W chould be pulling 9 amps! Just in range but close!

    For me i thinkt he cheapest oprion will be a mas/sproggy 4.5 (about 105 + any import) however Mtrix, yu may be able to answer this for me: what is this auto startup for cold starts about? can it be dissabled. I am pretty sure my PC is never gonna drop below 8V on startup as it is a small car and if the battery starts to show signs of weakness it is out of there before you can say "tank battery".
    Auto startup is that if your mobo doesn't have the option "Resume on power loss". If the mobo doesn't have the option, you have to manually push the power button to turn on the PC. The Auto Startup on this one simply "push" the power button for you. I am sure it can be disable by not solder on the relay/cap/resistor.

    The Sproggy may not provided enought juice during cranking if you are using 7200RPM HD. That is the problem I have with the old storck Toyota/Delphi battery. I have to upgrade to the Optima Redtop battery, but it is not 100% solution. With 5400RPM HD, it works and survice cranking 100%. I may have to build an extra 5V rail just to power the HD, DVD ROM if I keep using that 72K RPM HD.
    Once the engine runs, there was no problem.
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  10. #10
    FLAC
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    Got some actual figures for my intended system. I had to hold wires in place so I couldn't actually run the OS under real load to see what changes.

    Setup:
    Soyo K7-VME cheapo AMD m/b
    2500+ Athlon XP underlock to 1900+ (I believe last thing I did was underclock it - need to check once I'm not holding wires in place)
    Seagate barracuda 7200rpm drive
    256gb ultra low profile memory
    PW200-V clip-on psu
    12V from standard ATX desktop psu.

    I measure the current draw from the ATX psu into the PW200-V psu during a boot up to the logon screen.

    Immediately at turn on = ~5A
    Shortly into hard drive spinning up it hits ~6.3A
    Sitting at the logon screen = ~5A

    This is *way* better than I expected. I was thinking I'd be seeing more like 10-12A most of the time. I imagine the current draw will go up a bit when the cpu is fully pegged but I doubt it'll double . There's a chance my 7.2Ah sealed lead acid battery may be up to keeping the PC running long enough after I switch off the ignition for it to complete going into hibernate after all...
    Progress: 80% - Permanent install left.
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