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Pentium M ITX Build Power Issues

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First post, by rishooty

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So I've decided on a minimalist Win9x DirectX7 build and started on it over the summer. It was originally based on an EPIA-EN12000 board, but then I managed to find a Socket 479 board from BCM: http://www.bcmcom.com/bcm_search_results.asp? … roduct_ID=MX855. Itx pentium M boards have been nearly impossible to find in my experience, so I gladly took the option for a much more powerful cpu given the chance.

My original test build was as follows:

  • Antec 300-150 (comes with a proprietary 150W psu)
    PSU Ratings: +5V=10, +3.3V=8, +12V=10, -12V=0.2, +5VSB
    EPIA-EN12000
    512MB of DDR2 400
    Slim LG DVD Drive, GCT0N
    Generic 120GB 2.5" 5400rpm Sata Drive + IDE to sata adapter
    EVGA Geforce FX5200 PCI, Low Profile, 64-Bit
    2x80mm Noctua Redux 1200 Fans

Besides the fact that I didn't know the EPIA didn't have an IDE compatibility mode, it worked fine. I just couldn't finish the installation because I didn't have another adapter to use both the dvd and the hdd at the same time. Realizing this fact, and the fact that its digital audio out was a pain to get working with anyway, I decided to switch to the socket 479.

This time around I got a standing IDE adapter to save space, the kind that needs to be powered separately from the drive itself. Now lacking one less fan header from the cpu cooler and needing one extra molex from the adapter, I initially had the dumb idea of daisy chaining the PSU's single molex --> power for SATA2ide adapter and Drive --> power for standalone sata2ide adapter --> molex to 3 pin fan header. I was just too used to overpowered psus that could handle practically anything, so of course, this caused random freezing or no display on starts. I realized the issue when I noticed everything would be fine when I disconnected just about anything, be it the sata adapters or just the FX5200.

I was confused at first and wondered how it could be so power strained when people have reportedly used this case+psu combo with R7 250's, GTX 750 Ti's, and 7750's + i3's or Pentiums with zero issue. Between a number of vogons searches and use of outervision psu calculator, I had just now learned that older GPUs have vastly different power requirements. That is, modern ones use the 12v+ rail and old ones are especially heavy on +3.3v and +5v.

To remediate this issue I've ordered:

  • Another power+sata2ide adapter, the standard one from startech. I plan on powering it with a SATA to Floppy adapter so that both adapters don't share the same line.
    A sata extension cable to go with the above, as it cannot be plugged in directly where the hdd is mounted. This is why I tried the standalone standing adapter to begin with.
    A standard fan splitter so the 2nd fan can just be powered by the fan header instead of chaining off another line.
    A Geforce MX4000 for very cheap, as it looks like it fits within the psus requirements a bit better.

So while I have a planned solution, I'm wondering if I'm already in over my head and dealing with such a weak power supply isn't even worth it. Would I be better off switching back to the EPIA-EN? Would downgrading to the MX and separating my power sources help as much as I think it would? Should I just switch to another minimalist case like say, the Geeek A20 so I can at least use a FlexATX? Let me know your opinions. Upgrading the PSU baiscally isn't an option, because the PicoPSU160 or similar has essentially the same ratings.

Reply 1 of 2, by bakemono

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I used to run a Pentium M in a cooler master case with 150W PSU, and then for a while I had it in an old Compaq Deskpro case with a 145W PSU. I had a Geforce 4 MX PCI card and 3.5" HDD and never had issues. So I went down and looked at the ratings on these power supplies. They are a bit higher on the 5V and 3.3V with 12A and 14A. Maybe that's what makes the difference.

Sometimes external drive enclosures or USB-IDE adaptors come with a separate power supply (brick or wall-wart style), maybe you could use one of those to take some load off the internal PSU.

Reply 2 of 2, by rishooty

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Thanks for taking the time to look at them. Nice suggestions if I were really desperate, but I've confirmed with a bunch of outervision experimentation that the biggest load is, in fact, my DVD drive and either gpu of choice. That's good to note you used an MX series gpu though, it is lighter on the 5v rail. I still think I just overloaded the one molex trying to power 3 things but I'm not sure. Won't find out till most of my stuff shows up. Of course if it still doesn't work even with an MX and more separation of power between cables, I probably would be better off installing the OS and games via USB. In which case I'd be better off switching cases.

[Update] My cables showed up, and separating the power sources coming out of the psu DID help but not much. All that happened is that the no display boots and crashes happened far less often, but they still happened. So I have to wait for my MX4000 to come in to know for sure. Besides that, It's either reduce the load further by using a 2.5" IDE+Laptop IDE Disc drive to eliminate the need for adapters or switching to a FlexATX case. I'm looking at the Geeek A20 if I were to stay low profile, or the Geeek A30 with a dual PCI riser so I can get a sound card too. However, all the board says on shared pci slots is to make sure the drivers for said devices support shared irq. Of course, this is all assuming the MX4000 doesn't work. It's just annoying because this is the smallest case I could find with a disc drive. I honestly only wanted the disc drive as an excuse to collect games, but it seems not worth it on the itx end unless you want something above 8-10 liters.

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