The World's Most Powerful iMac G4...so far...

Discussion in 'iMac Mods' started by rpster, Mar 8, 2017.

  1. rpster

    rpster

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    Mar 8, 2017 at 1:46 AM #1
    rpster

    rpster

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    The World's Most Powerful iMac G4...so far...
    What does that mean, "most powerful"? Is it processing power? Power consumption? Graphics power? This build is a two-year culmination of a project that attempts to answer just how much power you can fit in an iMac G4.

    IMG_2333.jpg
    Ok...pretty par for the course as far as iMac G4 mods go. It runs Windows 10 because of the lack of hardware support in OS X...Wait a sec...

    IMG_2337.jpg
    Yep, that's a GTX 1060 with a Skylake i7. Ok ok, I know you're probably calling shenanigans at this point. Maybe I'm just using the case as a fancy monitor stand and have the computer in some box elsewhere. But I assure you this isn't a joke...

    Specs
    • 17" LG LP171-WU6 1920x1200 LED-backlit LCD Panel
    • Intel Core i7 6700T 2.8GHz CPU @ 35W (Turbo Boost up to 3.6GHz)
    • Noctua NH-L9i Low Profile Cooler
    • eVGA GTX 1060 6GB Superclocked GPU
    • Gigabyte GA-H110TN Thin Mini-ITX Motherboard
    • 16GB Crucial DDR4 2133MHz RAM
    • MyDigitalSSD BP4e 256GB mSATA SSD
    • MeanWell EPP-300-12 Open Frame Power Supply with PFC
    IMG_2342.jpg
    The exterior is largely unmodified save for a small bump on the back of the LCD enclosure. This was necessary to provide enough depth for the new LCD panel controller board. The modification is acrylic and has been cut, sanded, and painted to match the look and finish of the original enclosure as closely as possible.

    IMG_2339.jpg
    IMG_2340.jpg
    Around the back we have the modified ports. From L-R: Kensington lock, Full size HDMI 2.0 (4k@60Hz), 3x USB 3.0, Power Supply On-Off, IEC C14 AC Power input, Modem (disconnected), Ethernet 10/100, Apple Digital Audio (disconnected), Headphone, Mic In, Start/Shutdown Switch.

    LCD

    IMG_2344.jpg
    Removing the LCD is the same as on the original, except the LCD is now affixed to the front bezel. Aluminum foil has been added with copper tape to prevent light bleed into the enclosure.

    IMG_2349.jpg
    On the frame, we see the LCD controller board. The neck has been rewired with an HDMI cable and 12V+ power. The metal pieces seen on either side of the frame are mild steel bars added to help counterweight the neck. The new LCD panel is substantially lighter than the original.

    The metal frame at bottom right was cut to provide space for the controller board buttons. This was later found to be unnecessary as the controller board auto detects inputs.

    IMG_2348.jpg
    Detail of the controller board. Plenty of controller boards like this are available from your favorite Chinese warehousers. All you need to do is match the LCD part number.

    Base
    IMG_2350.jpg
    IMG_2351.jpg
    Looks normal til you take off the bottom cover panel.

    IMG_2352.jpg
    Contrary to the original design, I built the entire computer to be attached to the bottom half of the base. After disconnecting the Ground, HDMI, Speaker, and LCD power, the bottom half containing the whole computer can be removed.

    IMG_2353.jpg
    Here it is! Everything is in there. Computer, GPU, Power Supply, everything! This view is the base as seen from the optical drive opening. Note that no modifications have been made to the new hardware at all. Only cables were modified, which makes swapping hardware in the future a real benefit.

    IMG_2354.jpg
    The mini-ITX board is rotated a few degrees from straight in order to accommodate the mounting hardware that joins the top and bottom halves of the base. In this view, the GPU is mounted on a sheet of FR4 that is rigidly floating over both the CPU and power supply.

    Cooling has been reversed from the original configuration (Cold air from bottom > Hot air out the top). The single 120mm Noiseblocker-eloop B12-P PWM fan provides cool fresh air for the entire computer. More details on temps below.

    IMG_2355.jpg
    Rotating the base clockwise 90 degrees, the 300w power supply comes into full view. The power supply is a Meanwell unit that takes in 120-240VAC (at right) and converts it down to 12V (at left). The Thin Mini-ITX board takes 12V in. This negates the need for a Pico PSU and/or any other unit that would require an ATX connector. I'll talk about how the GPU is powered a little later.

    IMG_2356.jpg
    Rotating another 90 degrees we see the ports of the GPU and Motherboard. Various connectors for the I/O were purchased, custom cables were hand soldered, then fixed into the back panel using epoxy putty. Again, no modification of the motherboard or GPU.

    IMG_2357.jpg
    Last view showing the PCI-Express 3.0 4x connection. Wha??? A GPU not using 16x??? Relax...there are plenty of studies out there that clearly show that it makes little to no difference (1-2%), especially with PCI-E 3.0 connections.

    Also seen are the Headphone and Mic-In ports. Since they use the Intel HD Audio header, they automatically activate when a cable is plugged into either. The original power button was also reused.

    Performance

    Heaven-1060.JPG
    1640s in Heaven @ 1080p 8xAA Ultra...in an iMac G4 :)
    GPU clocks will spike to 2012MHz before settling down in the high 1800MHz.

    cinebench.JPG
    Decent Cinebench numbers. Low clocks are the biggest downside of this CPU

    Why didn't I go with a standard 6700? Or a faster clocked CPU?
    Heat. Too much of it in such a tiny space. The GPU already outputs 120w of heat, which leaves very little thermal envelope for the rest of the system. Remember that the iMac G4 enclosure was originally designed for a system producing about 120w.

    Since I am currently using this system as a daily driver, I also needed the extra thread support for applications other than gaming.

    Thermals
    I am happy to report there hasn't been any thermal throttling. Thermals are in line with most modern AIOs. CPU idles at 30-35c, while the GPU idles at 24-28c. Prime95 runs can get the CPU up in the high 70c range. Heaven gets the CPU into the high 60c range and the GPU into the 75-80c range.

    The only downside of my fan configuration is that the intake fan is controlled by the motherboard, and not the GPU. The GPU drives a smaller 40mm fan that provides additional airflow for the PSU. I am considering swapping this in the future. All it means is that I currently have to manually adjust the fan profile before starting heavy workloads or gaming.

    Power
    At idle, the entire system, LCD included, uses about 55w. Running Furmark will get usage up to 220W. This is well within the capabilities of the power supply.

    I'll take this time to explain what's needed to power the GPU. Many of you know that most mid-range and higher GPUs utilize supplemental power connectors in addition to the power provided through the PCI-E slot. In the case of my motherboard, there is only a 4x PCI-E slot, which will provide a maximum 25W instead of the 75W on a 16x slot. The GTX 1060 will consume up to 120W through the supplemental connectors and PCI-E slot.

    Normally, an ATX power supply would provide power to the supplemental connectors only at system startup, then switch off when the system powers off. Only problem is that my power supply stays on all the time. By adding a relay that triggers when power is provided by the PCI-E bus, the graphics card is switched on at the same time the rest of the system is. This relay also provides power to the PCI-E connector of the GTX 1060 via a modified PCI-E cable that isolates the motherboard's 12V rail from the 12V coming from the power supply.

    Conclusion
    This is not intended to be the ultimate iMac G4 build. There are plenty of other builds that do a fantastic job of melding the original functionality of the iMac G4 with newer hardware such as those by many of the users here on TonyMacx86.

    This build on the other hand, shows that there is plenty of power to be squeezed out of a tiny 3L enclosure :)

    Thanks for reading!

    Rpster
     
    Last edited: Mar 8, 2017
  2. JRDN

    JRDN

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    Mar 8, 2017 at 5:38 AM #2
    JRDN

    JRDN

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    Confused how you have the eloop mounted. They come out of the frame like that?

    have you looked into the 20” g4? Could there be a display that’ll fit that as well?

    Nice job!! Looks like a very tight fit
     
  3. rpster

    rpster

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    Mar 8, 2017 at 6:47 AM #3
    rpster

    rpster

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    The fan is first cut away from the frame near the rotor (had to commit to possibly destroying the fan). I then mounted it with 3M VHB tape onto an FR4 board that is custom cut to line up with the original fan mounting holes on the GPU heatsink. The original GPU fan screws are used to secure the FR4 board. Works great, low noise, and is super secure.

    I went with the 17" mainly because I was able to find an LED-backlit display for it. It uses less energy than the original CCFL panel which was important for this project. I tried looking for a 20" 1920x1200 LCD panel, but it looks like the last one went out of production a few years ago and the only device known to have ever used it is the HP HDX 9000 laptop. No LED-backlit 20" 16:10 panels exist to my knowledge.

    If I can find that 20" 1920x1200 panel, then I think an upgrade is due...
     
  4. MacTester57

    MacTester57

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    Mar 12, 2017 at 7:34 AM #4
    MacTester57

    MacTester57

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  5. yangbao111

    yangbao111

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    Mar 13, 2017 at 3:06 AM #5
    yangbao111

    yangbao111

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    I always want something like this!:clap:
     
  6. superslurt

    superslurt

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    Apr 5, 2017 at 10:27 PM #6
    superslurt

    superslurt

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    This is an amazing build! Very well done. Looks a lot tidier than mine :clap:
     
  7. colingmo

    colingmo

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    Apr 8, 2017 at 9:35 PM #7
    colingmo

    colingmo

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    Very impressive build, a small system that packs a big punch. Is the fan noisy?
     
  8. 68Electra

    68Electra

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    Jun 15, 2017 at 11:25 AM #8
    68Electra

    68Electra

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    How loud are the fans? I guessed it was either hot or loud (or maybe both!) until I saw th 35w TDP CPU.
     
  9. Cang

    Cang

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    Jun 21, 2017 at 7:16 AM #9
    Cang

    Cang

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    Really impressive work! That is exactly what i want built.

    want to know more details about the relay. how you connected it to the PCI-E bus?
     
  10. aquelito

    aquelito

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    Jun 21, 2017 at 4:27 PM #10
    aquelito

    aquelito

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    Hi there,

    Very interested by your project as I'm currently running a very similar setup with a powered custom riser and a GTX 1050 Ti, powered by a single 12V AC Adapter.

    I am very interested by the relay triggered by the PCIe bus. This is an issue I had also anticipated - as I do not like my GPU and riser being constantly fed with 12V - but not able to solve by myself.
    Can you elaborate a bit more ?

    [​IMG]
     

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