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.

Pico-itx

      - 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.

KEEX-4030

- 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 logicsupply.com 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.

The 17" Mod Success Stories, Mistakes, and All-In-Ones

As I just wrote on my 17" iMac G4 guide, I have been exploring simpler ways of converting the iMacs LCD to a plug and play DVI/HDMI compatible monitor.  Do to an upcoming test I have to put this project largely on hold for the next few weeks.  Regardless, people have been doing great and over the past few months I have gotten emails of no fewer than 10 successes.  Many from people with limited electronics experience.  Thank you to everyone who has shared this me, its extremely rewarding to see that my projects have helped others doing the same.  I hope to see plenty of broken iMac G4's returned to their proper place on the desktop for years to come.

Courtesy of mouser.com

I have unfortunately wasted time going down a dead end route.  After much searching I was finally able to locate the motherboard receptacle for the iMac G4's video cable.  For those interested it is the 21pin - C seen in the diagram to the right.  Specifically its the: 656-FI-WE21P-HFE JAE FFC / FPC Connector.

My hope was to create an adapter wire that you could simply plug into the iMac's video cable.  It would have a DVI/HDMI out and cables that could hook to a power supply.  Add the inverter and presto, instant iMac conversion.  Unfortunately the ones that are soldered on boards need to be ordered in the thousands.  The actual connectors themselves are too difficult to work with unless pre soldered to a board.  I've tried but the pins coming off very small and the crimping tool that you can buy is around a thousand dollars.  The current method that I'm trying the use seems much simpler (and cheaper).  I will detail it in the guide as soon as I complete it.

Top = MALE
Bottom = FEMALE

The biggest "correctable" error that people seem to be making involves using the DVI pinout as is with a male cable.  I talk about this in the post, but I think people are looking only at the pinout.  So I'm going to make it clearer and post a male pinout.  The DVI pin numbers are based on a standard numbering system which is numbered left to right based on the female DVI connector.  The female connector is what you plug a standard cable into, found n the back of a computer or graphics card.  The standard DVI cable has 2 male connectors at its ends.  So please keep this in mind when you do this mod.  You can certainly use a male interface, but you have to realize which pin is which number.  You can simply view it from the back to see how it relates to the female plug.


In regard to all-in-ones, they are certainly possible.  But just keep expectations in check.  You really can not fit much it the base.  And remember you have to power it.  Pico power supplies really are limited to about 150 watts so if you want and you can not fit an tax power supply in the base.  But, remember this is a 17" screen - you don't really need a powerful video card.  That said, I still firmly believe that a mini itx is too high a risk for overheating at the bottom of the dome and should not be used.  I recommend using a pico, nano, or embedded motherboard.  I'll be reviewing some of these choices in my next post.