World's Fastest iMac G4 - 2 GHz iMac G4 CPU Upgrade

Discussion in 'PowerPC Macs' started by dosdude1, Jul 1, 2018.

  1. dosdude1 macrumors 65816

    dosdude1

    Joined:
    Feb 16, 2012
    #1
    Well, after a lot of research and a good bit of info from @LightBulbFun, I finally managed to pull off something I've been working on for quite some time now... Making the world's fastest iMac G4. Back in the day, a company called "DayStar" used to perform such an upgrade for people, installing a G4 CPU (speculated to be a 7447), and clocking it to 1.92 GHz. Well, I thought I could do better, and indeed I have.

    Let's start with the CPU. I decided to go with a 1.67 GHz MC7447B CPU, taken from a 15" PowerBook G4 logic board. Not only are these CPUs much cooler-running than the stock MC7445 CPUs used on these model iMac G4s (1.0 - 1.25 GHz models), but they also, obviously, have a higher rated clock. This means, that with the thermal capacity of the iMac G4's cooling system, we should be able to get a decent overclock out of it. The iMac G4 board also supplies the CPU VCORE rail with around 1.5V, which is just perfect for a 7447.

    Now, the main issue I ran into: Firmware. As I found out (the hard way), a system firmware patch is required in order for the system to be able to boot with a 7447 CPU installed. I didn't realize this, and went ahead and soldered one onto my 1.25 GHz 17" iMac board. Of course, the board would no longer POST afterwards. Fast-forward quite a few months, though, and @LightBulbFun comes in with a solution: A firmware patching utility, designed for use with Giga Designs CPU upgrade cards for use in certain PowerMac G4 models. Since my iMac was no longer working, I couldn't actually test it, but luckily I had a spare board from a slightly less powerful 1 GHz model iMac G4 (which also only had USB1.1 support and a worse video card). Even though this was not the board I was hoping to upgrade, I figured what the heck, and proceeded to run the firmware patcher on the machine. To my amazement, the firmware patch completed successfully!

    IMG_7566.jpg

    In my excitement, I got to work immediately reballing a 7447, desoldering the original 1 GHz 7445 from the board, and finally soldered the 7447 onto the board. I then hooked the board back up to the system, turned it on, and it POSTed!

    Lastly, I needed to set the PLL configuration resistors on the board to get the CPU clocked up to my target 2 GHz clock speed. Based on the schematic for the board, some info from @LightBulbFun, and a guide I found online, I set the PLL configuration appropriately (15X multiplier @ 133 MHz bus speed), assembled the machine, and proceeded to run some stress tests. It worked 100% the entire time, and seemed to run relatively cool as well. I would definitely consider this a successful upgrade, and I now indeed have the world's fastest iMac G4! My Geekbench result can be viewed here.

    Now that I successfully completed this upgrade, I can now offer it as a service to anybody located in the US. If you are interested, please feel free to PM me!

    IMG_7569.jpg IMG_7570.jpg IMG_7571.jpg IMG_7572.jpg IMG_7573.jpg IMG_7582.jpg IMG_7583.jpg
     
  2. Daniël Oosterhuis macrumors 6502a

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    Jan 10, 2016
    #2
    It was quite amazing to see this all come together so well. Really great work!
     
  3. AphoticD macrumors 65816

    AphoticD

    Joined:
    Feb 17, 2017
    Location:
    Australia
    #3
    Well done @dosdude1 and @LightBulbFun !!

    It’s amazing to see a single core G4 crack 1000 points!

    This is the kind of hardware hacking that leaves Hackintosh mods in the dust.

    Which other PowerPC Macs would be good candidates for the upgrade?
     
  4. weckart macrumors 601

    Joined:
    Nov 7, 2004
    #4
    I saw a Cube power adapter in one of the photos. I wonder if that’s next?
     
  5. Amethyst1 macrumors regular

    Amethyst1

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    Oct 28, 2015
    Location:
    Germany
    #5
    Awesome, great work there! A 20-inch iMac G4 running at 2 GHz with 2 GB RAM and an SSD would be my dream machine :) I wonder how it compares to a 2 GHz iMac G5 in terms of performance?

    On a different matter, has anyone experimented with overclocking a 1.67 GHz PowerBook (DayStar offered 1.92 GHz upgrades for PowerBooks)?
     
  6. CooperBox macrumors 6502a

    CooperBox

    Joined:
    Nov 28, 2010
    Location:
    France - between Ricard & Absinthe
    #6
    @dosdude1
    An excellent project and end result! In fact if I was your side of the pond, assuming a realistic price for the upgrade I'd come knocking on your door, as I have several iMac G4 1.25 GHz models in my reserve which would love such a transplant. Just for general interest, myself (and I'm sure others) would love to see a YouTube video of the iMac booting and running in this config.

    @LightBulbFun
    Given that you mastered the Pismo G4 upgrade, is this a project that you may have eventual plans for?
     
  7. LightBulbFun macrumors 68000

    LightBulbFun

    Joined:
    Nov 17, 2013
    Location:
    London UK
    #7
    Very nice work :) as mentioned above its very nice to see this all finally come together

    for anyone wondering yes we have thought about what a 7448 might do on this system, and we suspect it may work but its a lot of work to BGA Swap chips and I think @dosdude1 is all BGAed out atm :) (You have no idea how many times he had to swap chips back n forth, but we did discover that a PowerMac6,3 will chime with a PowerBook5,6 BootROM who knew... :D ) also to get a 7448 working we need to lower the Core voltage stock it runs at 1.5-1.57V (Depending on if its the 1Ghz or 1.25Ghz model) and while 1.5V is exactly the voltage we need to push a 7447B to 2Ghz its above the max safe voltage for a 7448 which is 1.4V, so we will have to tackle that issue, should not be too hard to do tho since I have schematics and I have already discovered which resistor we need to change to change the Core Voltage.

    I can do a 360 pin cBGA chip no issues :)

    one of the big issues here has been the software side of things, because Apple makes the Machine halt/not post if the BootROM detects and unknown CPU

    and that leads onto your question, right now as it stands, we dont have a tool that can patch any BootROMs newer then 4.6xx and the iMac G4 USB 2.0 quite a few of them are PowerMac6,3 with 4.7.xx BootROMs I dont think the GigaDesgines patcher can handle that ROM version, so right now we cant offer an upgrade service for that machine.

    however I did notice that some 1.25Ghz iMac G4s are PowerMac6,1 with 4.6.xx BootROMs it MIGHT be possible to patch those with the GigaDesgines Firmware patcher but that is currently untested. (im curious what the difference between the 1.25Ghz PM6,1 and 6,3 is, I personally suspect that PM6,3 4.7xx might have OOB 7447 (no suffix) support, however we dont have any 7447 (no suffix) chips to test this theory with. )

    If anyone has the Firmware patcher DayStar included with their G4 CPU upgrades (even their PM G4 ones) please let us know and send us a copy of it :)

    also I dont have a large cache of suitable 7447B chips for performing the 2Ghz upgrade on suitable PowerMac6,1 models, however luckily for us we can salvage chips off of bad 1.67Ghz PBG4 motherboards :)

    (however if anyone in the US is interested in having this done IIRC @dosdude1 does have a few 1.67Ghz 7447Bs kicking around ;) )
     
  8. DearthnVader, Jul 8, 2018
    Last edited: Jul 8, 2018

    DearthnVader macrumors 6502a

    DearthnVader

    Joined:
    Dec 17, 2015
    Location:
    Red Springs, NC
    #8
    The 7478 is pin compatible, but I read that you have to terminate some of the traces to do a 7447>7448 swap. Not sure how this applies to a 7455>7448 swap.

     
  9. dosdude1 thread starter macrumors 65816

    dosdude1

    Joined:
    Feb 16, 2012
    #9
    Well, I have just confirmed that BootROM version 4.7 is indeed patchable by the Giga Designs patch. So, that means ANY 1/1.25 GHz iMac G4 can be upgraded to a 7447 CPU. I have also attempted manually patching the firmware on a G4 Mac Mini and upgrading that to a 7448, but unfortunately it doesn't work... There must be some hardware incompatibility with the 7448 on these systems.
     
  10. seveej macrumors 6502a

    seveej

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    Helsinki, Finland
  11. cernorama macrumors newbie

    cernorama

    Joined:
    Jul 17, 2018
    #11
    the 745X and 744X are incompatible BGAs
    --- Post Merged, Jul 17, 2018 ---
    Collin: HOLD MY BEER I CAN DO BETTER
    --- Post Merged, Jul 17, 2018 ---
    found 7448 donor chips here only 29.99 + s/h...

    https://www.ebay.com/itm/X-ES-SBC-X...nkw=7448+cpu&_from=R40&rt=nc&LH_TitleDesc=0|0
     
  12. dosdude1 thread starter macrumors 65816

    dosdude1

    Joined:
    Feb 16, 2012
    #12
    Well, as if the first mod wasn't enough... Here we are again, this time with a better board (GeForce FX5200, USB2.0), AND an MC7448 CPU installed! This time, it was a bit more difficult. First thing I needed to do was reduce the core voltage from its stock 1.57V, to a voltage of 1.4V or lower (1.4V is the max voltage that the 7448 can handle). I found that replacing R388 (shown below in BoardView) with a 348K resistor got the voltage down to 1.39V, just under the max rating of the chip to allow for decent overclocking headroom. Then, I reballed and soldered the CPU onto the iMac logic board. While the machine initially powered on and worked with the 7448 CPU soldered on, it wouldn't boot OS X. Luckily, I was able to find the solution in a NewerTech firmware updater, once again designed to add support for 7448-based CPU upgrade cards in PowerMac G4 systems. This solution was an NVRAMRC script, that needed to be added to my iMac's NVRAM. To do this, I first applied the NVRAM patch on a PowerMac G4 system that this FW updater was designed for, as it would not run on the iMac G4. Then, I copied the variable it added to NVRAM using "nvram -p" in OS X, then manually set that variable in OS X on the iMac G4. Luckily, I was able to get OS X to boot on the machine BEOFRE applying the NVRAM variable thanks to @LightBulbFun's modded 10.4.11 kernel, allowing it to boot on CPUs it doesn't recognize. Though, booting without the NVRAM variable patch applied meant that no L2 cache was detected. After setting the NVRAMRC script on my iMac, it booted right up with stock OS X kernels, detected L2 cache, and worked perfectly! Now I began trying to overclock the CPU. This being a CPU only rated at 1.4 GHz, I was only able to get it to run stable at 1.92 GHz. When clocked to 2 GHz, the system would either kernel panic or completely lock up when under load. Still, even at 1.92 GHz, it performs about the same, if not slightly better in some instances than the previous 2 GHz 7447-upgraded machine, while running quite a bit cooler. Overall I'm very satisfied, and hopefully one day I'll be able to source some higher-rated 7448 CPUs.

    Side note: Somehow, my iMac's internal LCD stopped working during the testing process. I'm not sure what happened, but now the screen will only show white, and not an image. Hopefully I'll be able to figure that out, but that is why I'm using an external display in the pics.

    37278573_1610994935693051_8277664124251406336_o.jpg 37279913_1610994835693061_5665527094281502720_o.jpg 37293819_1610994945693050_2750267035089895424_o.jpg 37316372_1610994919026386_4614661984086917120_o.jpg 37375464_1610994862359725_6663027776989167616_o.jpg
     
  13. DearthnVader macrumors 6502a

    DearthnVader

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    Dec 17, 2015
    Location:
    Red Springs, NC
    #13
    @dosdude1 Great work. Do you think you can offer a 7448 upgrade service?

    I have a few iBooks in need, also if you run across a 750fx with a higher spec( 900mhz to 1.1 Ghz ) I'd pay to have my iBook G3 600 16MB Vram updated to a better CPU.
     
  14. dosdude1 thread starter macrumors 65816

    dosdude1

    Joined:
    Feb 16, 2012
    #14
    Yes, once I get some more chips in stock, I can indeed offer it as a service. It should be possible on iBook G4s and aluminum PowerBook G4s as well.
     
  15. LightBulbFun macrumors 68000

    LightBulbFun

    Joined:
    Nov 17, 2013
    Location:
    London UK
    #15

    its very cool to see this project finally come to ahead :)

    there was a LOT of work involved. but its all worth it :) (I managed to remote into OpenFirmware from across the globe which was quite fun :D )

    to give someone a sense of scale of how much of an upgrade this is

    the 7445 has 256KB of L2 cache the 7448 has 1MB of full speed 1:1 on die L2 cache thats Four! times the amount of L2 cache of the iMac G4s stock CPU and considering how bus constrained G4s are we need all the L2 we can get :)

    also since the 7448 worked on the iMac G4 board which is one of the first 744x 360CBGA macs, if we can figure out the firmware patches we should be able to upgrade any Mac with a 7445/7447/7447A/B to a 7448 :) imagine how Fast OS 9 would be on one of these systems :eek: (from what it looks like Macs with BootROM versions 4.7 and lower we can patch but 4.8 and above is currently playing difficult)

    it would be fun to find some MC7448HX1700LDs those are the fastest 7448s Made rated for 1.7Ghz, if a 1.4Ghz 7448 can hit 1.92-2.13Ghz (I have seen 1 of these 1.4s hit 2.13Ghz on another system) imagine how fast a 1.7Ghz 7448 could clock to... its a shame 7448s are so hard to find


    I have some 750GX/GL CPUs which are compatible with the 750FX so I plan to try and swap onto my 800Mhz 750FX iBook G3 :) (the 750GX/GL has 1MB of L2 vs 512KB of the 750FX/FL) ill let ya know how that goes
     
  16. Expobill macrumors 6502a

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    May 30, 2018
    #16
    I would be happy just to get the g4 iMac downstairs to compute something besides the grey screen with the Apple logo
     
  17. Jiggly Billy macrumors member

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    Nov 2, 2012
    #17
    I wonder, how feasible would this be with an eMac logic board?
     
  18. Daniël Oosterhuis macrumors 6502a

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    Jan 10, 2016
    #18
    The later models do use the right CPUs for such a swap. Specifically the 1.42GHz model is running a 7447, so it could physically be upgraded to a 7448. And the 7447 can already hit 2GHz with some luck in an eMac thanks to the overbuilt thermal system, so imagine what a 7448, especially a higher clocked one could do.

    What I'm not 100% sure on is whether the BootROM revision throws a wrench into this or not. Paging @LightBulbFun to answer that one :p
     
  19. LightBulbFun, Jul 18, 2018
    Last edited: Jul 18, 2018

    LightBulbFun macrumors 68000

    LightBulbFun

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    Nov 17, 2013
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    #19
    indeed if we can figure out the BootROM situation we should be able to 7448 a 1.42Ghz eMac

    however I just did a bit of research and it looks like the 800-1Ghz ATI Radeon 7500 eMacs used 7445 CPUs and the reason this is significant as im pretty sure these will have BootROMs that we can patch which means we can stick a 7448 on them :) also they also run OS 9.2.2 natively so once fitted with a 7448 they would make for a killer OS 9 machine :D

    (the First gen 700-800Mhz eMacs and iMac G4s use 7450 CPUs which in theory we can upgrade to 7457s but the 7448 is not pin compatible with the 7450/7455/7457 line of CPUs)

    (edit: basically as of current any Mac with a 7445 or older we are pretty sure that we can patch the BootROM of to work with newer CPUs however 7447 and newer Macs are are still working on getting those patched)
     
  20. Jiggly Billy macrumors member

    Joined:
    Nov 2, 2012
    #20
    I don’t know if it would help or not, but I have a 1.25 USB 2.0 model that I picked up today ($15. I really just wanted the pro mouse and keyboard but whatever!). I doubt that uses the 7447 though? Or would that be the same CPU used in the 1.25 USB2 iMac?
     
  21. Daniël Oosterhuis macrumors 6502a

    Joined:
    Jan 10, 2016
    #21
    That does use a 7447 processor, but the problem is that it likely is on BootROM 4.8.xxxx, which hasn't been able to be patched yet. A System Profiler shot would definitely help narrowing that down though.
     
  22. Jiggly Billy macrumors member

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    Nov 2, 2012
    #22
    BootROM 4.8.8f0
     
  23. LightBulbFun macrumors 68000

    LightBulbFun

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    Nov 17, 2013
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    London UK
    #23
    as of writing this post we cant patch that BootROM to enable unsupported CPUs to work. however @dosdude1 has bought some more tools that should let him read NWR Mac BootROM EEPROMs in an external programmer so we can poke at things without the risk of bricking a machine :)

    as it stands currently we should be able to patch BootROMs 4.7xxx and lower :)
     
  24. cernorama macrumors newbie

    cernorama

    Joined:
    Jul 17, 2018
    #24
    i been looking for 7448's and they are very hard to come by cheaply, i was lucky to point dosdude to 10 , the actual upgrades from newertech and powermax aren't cheap either, unless you come across one in a machine and people have written it off without knowing what is it...
     
  25. LightBulbFun macrumors 68000

    LightBulbFun

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    Nov 17, 2013
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    London UK
    #25
    indeed they are very hard to come by sadly, I am well aware of their scarcity

    we have been aware of those 7448 SBCs for a good year or 2 now (its where the 7448 used in the iMac above originated from :) ) with confirmation that indeed we can make 7448s work @dosdude1 struck a deal with the ebay seller and he bought 6 of the units to pillage for 7448s.
     

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