Friday, September 30, 2011

Mini-itx Problems, SBCs and Embedded Boards

Base with Drive
When making an all-in-one you have to realize the base of the G4 is very small - Much smaller than you think.  The faraday cage inside provides all the real "support" of the base.  Unfortunately 4 steel "legs" make it even tighter.  Below the drive pictured here there is only about 1/2" inch.  The iMac was convection cooled so everything just stacked on top of each other leaving no room for airflow.  Below is how an atom mini itx board with standard fan and heatsink looks interns of thickness next to the original iMac G4's motherboard.  Remember the drive sits right on top of the motherboard - there is no wiggle room.
This standard size fan takes up much of the room that the drive occupied as well.  Even above the drive there is minimal room (enough for a 3.5" hard drive and then a fan.  The power supply was actually split in two and placed on opposite sides of the hard drive.
Without having to grind down the faraday cage even fitting in a mini itx is difficult.  You have to put it in at an angle, accessing the ports can be difficult.

Even when using just a mini itx board, no optical drive, no graphics card, just a small hard drive, there are two problems with creating a "powerful" system: Power and Heat.

By power I am referring to where the power source goes.  No atx power supply can fit in any way.  The existing power supply is not compatible with atx and regardless the 17" is only 160watts.  Pico power supplies are really the only option and these are limited to about 150 - 175 watts.  Remember, some of this has to go to power the display, support USBs etc.

By heat I am referring to the very poor air flow of the steel faraday cage.  The only air entry points are some slits at the bottom and holes at the top.  You would never, ever choose this as a computer case.  The mini itx has to sit at the very bottom (its the only place it fits).  So anything else you want to put in the case - wires, wifi, optical drives, ssds, whatever, has to go on top of the board.  This further blocks air flow.  Trust me, even with pristine wire management anything other than a very low power system is going to have problems.  So you are VERY limit din what can go on top of the motherboard.  If you are building a system just to show that it can power on, a "proof of concept" then you don't have to worry.  But, if you want a stable, reliable system that you can use daily, there is a better way.  There are actually two options:

1) Go Big: You want the system you want.  Dedicated graphics, optical drive, big power supply.  Then go external.  This is the way I went with my mac mini setup and I couldn't be happier with it.  I went dual monitors and was then able to use the base to house the optical drive and 20" monitor power supply.  Keep in mind the iMac is a desktop, you aren't carrying it room to room.  This makes upgrades a breeze and you are no longer limited by size, heat, or power.

2) Go Small: What if you could fit a motherboard at the top of the dome.  The CPU sitting right under the ventilation holes would allow for some airflow.  What's more, this would allow you to use the space below however you see fit.  In my all in one I went with a bluray optical drive.  There are compact options beyond mini-itx.  These are usually referred to as either Single Board Computers or embedded systems.  Although most of these systems are not available from usual vendors such as amazon, newegg etc, they are still easily to obtain commercially.  I have dealt with many sales reps from the companies I am going to discuss and they have almost universally been very helpful.  These boards are sometimes more expensive then their commercial atx counterparts, sometimes less.  They tend to use laptop parts (which tend to be lower power and generate less heat).  They usually have on board power options.  Their expansion options are usually very limited (but there is really isn't any room in the dome for expansion).  They are usually associated with low power platforms but are NOT limited to these.  Many form factors are available, but I am going to focus on those that have I/O that is familiar and compatible with commercial products.  So lets see what's available.
Zbox Nano

1) The ITX's
- A) Mini-itx (170mm x 170mm) (6.7" x 6.7") - discussed above
- B) Nano-itx (120mm x 120mm) (4.7" x 4.7") - These are sometimes available from standard vendors.
     - I for one am very excited about AMD's fusion platform.  
       The Zbox Nano relies on a Zacate E-350 APU which yields on board AMD HD 6310 graphics.  This is available as a barebones system and although it comes with the zotac case, it can be removed.  If a hackintosh is your goal, this won't suit your needs.  But if you want low power, but some graphics power consider this option.

- C) Pico-itx (100mm x 72mm) (3.9" x 2.8").  You may not believe it, but this is a legitimate option.
      - While not my favorite platform, Intel's Atom, is certainly capable of being a machine capable of everyday, routine tasks.  And is available on most PicoITX bards.
Epic SBC

2) Industrial Computers 
- A) EPIC - Embedded Platform Industrial Computers (165mm x 115mm) (6.5" x 4.5").  These can blur the line between mainstream and industrial systems, but many have nothing but standard I/O and are have identical chipsets and features to the larger mini-itx boards.

3) Drive Sized Platforms
- A) 5.25" Embedded - (203mm x 146mm) (8" x 5.75") - designed to be the same size as a 5.25" drive.  Although longer then mini itx, its narrower shape is better for the iMac.  If you don't use an optical drive these may be considered (although they are on the larger size).  Available in everything from Atom, to Intel Core 2 Duo, to 1st and 2nd generation Core i processors.

- B) 3.5" Embedded/ECX - (146mm x 105mm) (5.75" x 4") - similarly designed to be the same size as a 3.5" drive.  ECX is an intel developed standard, meant to give the performance of mini-itx in a smaller form factor.  Similarly available in many varieties.  Global American again has a wide selection from Atom up to 1st generation Core i processors.  Two popular makers of these systems are Quanmax and Portwell.  Online distributors such as offer these boards.  For my All-in-one I used the Keex-4030, a Quanmax Core 2 Duo Mobile Processor Board.  I found it easy to use and it delivered solid performance.  A second generation core i/sandy bridge mobo has been announced by Quanmax, but I have not found it available yet.

I would probably recommend either Nano-ITX or 3.5" ECX as they offer the best availability, standardization, and size to performance ratio.  Just remember that a non-standard board may have some quirks (proprietary connectors, limited expansion).  Do your homework first, before buying.  But there are plenty of options for small motherboards beyond mini-itx.


  1. this is cool. i'm contemplating on doing this one day. before i stumbled upon your site, i was thinking on putting the guts of an hp mini netbook inside the dome. it seems to be almost all-in, all i need to worry about is how to power the 17" flat monitor. do you think this is a viable option?

  2. I honestly do not know how big the hp mini's logic board is so I don't know if it would fit. A couple things:
    1) Make sure it fits WITH THE CONNECTORS in place. DVI/HDMI/USB cables all add significant length. Even buying right angle connectors still takes up room.
    2) You will not be able to connect the iMac's LCD to the internal monitor cable. The laptop will not use TMDS which is the signaling type you need for this LCD. You must use the video out.
    3) The video out must be a digital signal such as DVI or HDMI. VGA out will not work without a VGA to DVI converter (and not just a simple DVI to VGA adapter).

    As long as those conditions are met and you power it, it should work like any other DVI monitor.

  3. JBerg,
    another very informative blog - thank you. I fully subscribe on the problems with MiniITX boards. I only know one MiniITX Atom board with a passive cooling and a very low height - it's the Intel D945GSEJT with only 2cm in height. Unfortunately it ships with only an Atom processor and only with GMA950 graphics - so forget about speed records.

    But even with this board it is still not possible to integrate a 5,25" DVD or BR drive. In my mod I used a Slot-In notebook drive, which causes additional problems with opening the drive door.

    Still I should mention some advantages of this combination: you do not need any fan (completely silent with an SSD) and the board comes with a switchable DVI or LVDS output, so one can replace the original screen with ones with higher resolutions (max 1680x1050). And it runs Mac OS X :-)

    I must admit the people from Apple really did a brilliant job in cooling the G4 over a heat pipe and the metal dome cage. The logic board is smaller in height than any other board I have ever seen.

    So from my current status of knowledge I would higly recommend your solution with the ECX board, would they even be available here in Germany for an affordable price...

    Best Regards,

  4. JL, I could not agree with you more. I am amazed at how many of these machines (almost a decade later) are still functioning. I have had plenty of desktops meet their demise over this period. Obviously, many iMac G4s have broken down, but finding an operational 15 or 17" is very easy. Finding a 20" can be more difficult, but isnt very hard either. It is a testiment to the quality of the engineering that a convection cooled, hot processor like the G4 can still function after a decade of use.

    I did not want to blog about this yet, but I am awaiting delivery of a KEEX-6100, which I plan to pair with a mobile sandy bridge i5 processor. I am hoping I have more success with a hackintosh with this board. I know exactly what you mean about passive cooling. I found the sound of the cpu fan quite annoying in my previous build. I was hoping to get your opinion on a couple ideas - I purchased 1 standard socket G2 fan and 1 passive heatsink. I was plannning on either positioning the passive heatsink right under the top and using only a system fan or taking a large heatsink and rigging up a giant passive heatsink at the top. i may even by an engineering sample cpu to experiment with. (Continued in next post)

  5. I have never rigged a heatsink before. To add a large passive heatsink And not interfere with the other motherblard components I have to "raise" the cpu. Is it reasonable to place a metal plate with large heatsink right on top of the small passive heatsink? I think I almost have to buy a CPU to experient with if I attmpt thid - do you agree?

    A couple things that are great about this board:
    LVDS and backlight power are on the board as well as HDMI and Displayport
    The chipset, onboard graphics, and processor are the same as the mac mini and should be comparable.
    There is an onboard audio amp, its only 2watts, but does allow for some interesting possibilities.
    its got 2 sata ports (hdd and dvd) and a mini pcie for some expansion
    it also retains the compact flash (dual boot?)

    All in all I am extremely excited. i am probably going to use the co 2 duo board (keex 4030) on my 17" tutorial that Im working on and use the Keex 6100 for my 20" tutorial to follow. Thank you again my friend and I appreciate all your advise/input.

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