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

Amethyst1 said:
IIRC @LightBulbFun got his 1.5 GHz G4 mini to run at 1.67 GHz so you could use that as a starting point. And yeah, let's build a watercooled mini :)
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it was a 1.42Ghz actually, been running without issue at 1.67Ghz for a couple years now amazingly despite the fact all I used was a pencil LOL :)

also running Mac OS 9.2.2 now :)

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(side note this was via the Atlona DP400 I was hoping it would offer me a 2560x1440 30Hz option but it just offers me the same rez settings as it does over single link DVI directly, so ill have to fire up switch rez one of these days)
 
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LightBulbFun said:
(side note this was via the Atlona DP400 I was hoping it would offer me a 2560x1440 30Hz option but it just offers me the same rez settings as it does over single link DVI directly, so ill have to fire up switch rez one of these days)
Click to expand...

The U2715H's EDID probably doesn't expose 2560×1440 at 30 Hz. I don't know if the DP400 simply passes through the monitor's EDID or "adds" one of its own. The P2415Q's EDID, for instance, exposes 3840×2160 at 30 Hz if it's set to DP 1.1 and this is what the SLSD/DP400 combo defaulted to. :)

While playing with SwitchRez, you could also try 33.9 Hz (134.75 MHz using CVT-RB) and 38.6 Hz (154 MHz), to see where the mini's limit is with this particular combo.
 
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Madness. That is so huge that if the mouse icon wants to travel from one edge to another, it needs to take a bus ride. :D
 
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dosdude1 said:
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!

View attachment 768625

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!

View attachment 768627 View attachment 768628 View attachment 768629 View attachment 768630 View attachment 768631 View attachment 768632 View attachment 768633
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I would be very interested in having this performed, but I can’t find a way to PM you.
 
So, i have a problem. i ended up killing my fx 5200 15" usb 2 boards cpu by accidently overheating it because im an idiot. i have since soldered on the 7447 1.42 out of an emac but now need a way to flash the firmware onto the eeprom without well, the system working. Any ideas?
 
Tremain said:
So, i have a problem. i ended up killing my fx 5200 15" usb 2 boards cpu by accidently overheating it because im an idiot. i have since soldered on the 7447 1.42 out of an emac but now need a way to flash the firmware onto the eeprom without well, the system working. Any ideas?
Click to expand...
The only thing you can do is get a TL866 (or other EEPROM programmer) with appropriate TSOP48 adapter. Then you can dump the ROM externally, patch it (you can send the dump to me and I can patch it for you manually), flash the modified dump back on, and solder the EEPROM back on.
 
dosdude1 said:
The only thing you can do is get a TL866 (or other EEPROM programmer) with appropriate TSOP48 adapter. Then you can dump the ROM externally, patch it (you can send the dump to me and I can patch it for you manually), flash the modified dump back on, and solder the EEPROM back on.
Click to expand...
Okay cool. Buying a new tool is always useful anyway. Thanks for helping. I'll message here once I have dumped the eeprom.
 
Tremain said:
Okay cool. Buying a new tool is always useful anyway. Thanks for helping. I'll message here once I have dumped the eeprom.
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You can actually push the 1.42 chips pretty high on the 2005 eMac. Have my 2005 eMac running at 1.92GHz @1.375V... though I would love to get someone to swap in a 7448 someday and get it to at least 2.08GHz, though from what I hear the chips are hit or miss. Right now I'm focused on getting a 7400 onto a Rev B iMac CPU card.
 
Hello! First, thank you very much for the post and the comments.

I write from Spain. I have a mac mini G4 1.25 overclocked to 1.5ghz. I have found on ebay G4 7447B processors at 1.667ghz, specifically HX1667ZF.

Could the Mac Mini's original 7447b processor be swapped out for this one, and get faster speeds? if so, what speed do you think it can reach with the factory voltage?

Since it is a 7447b just like the original, would it require a ROM Firmware update to boot it?

Thank you very much!!
 
indibil said:
Hello! First, thank you very much for the post and the comments.

I write from Spain. I have a mac mini G4 1.25 overclocked to 1.5ghz. I have found on ebay G4 7447B processors at 1.667ghz, specifically HX1667ZF.

Could the Mac Mini's original 7447b processor be swapped out for this one, and get faster speeds? if so, what speed do you think it can reach with the factory voltage?

Since it is a 7447b just like the original, would it require a ROM Firmware update to boot it?

Thank you very much!!
Click to expand...

the 7447B can indeed be swapped straight in, you dont have to worry about any sort of firmware patching in your case

what speeds it can reach with the factory voltage is hard to say, depends on what the factory voltage is set too!

I imagine you would be able to at least hit 1.67Ghz tho
 
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LightBulbFun said:
the 7447B can indeed be swapped straight in, you dont have to worry about any sort of firmware patching in your case

what speeds it can reach with the factory voltage is hard to say, depends on what the factory voltage is set too!

I imagine you would be able to at least hit 1.67Ghz tho
Click to expand...
I have not found anywhere how to modify the voltage of this equipment, I do not know if it is worth changing the CPU, if later I will not be able to increase the speed. I suppose that, as you say, I will be able to reach a minimum of 1.67GHz.

Thank you!
 
Hello.

I can't find the resistor combination for speeds above 1.58ghz on a Mac Mini G4. Does anyone have the table with more combinations?

Thanks.
 
indibil said:
Hello.

I can't find the resistor combination for speeds above 1.58ghz on a Mac Mini G4. Does anyone have the table with more combinations?

Thanks.
Click to expand...
Yes, here you go. I had a thread on macos9lives where I was cobbling some info together.

I have my 1.5GHz Mac mini G4 running overclocked at 1.8GHz nicely with the stock cooler.

But after a wild ebay shopping spree on cheap Motorola G4 cpu's I may attempt replacing the original 1.5 with the 1.67Ghz and going for 2GHz+. But I need to build up some confidence first : )

I also wonder, with the Mac Mini 1.5, it has 64gb of vram vs 32gb on the other mini's, would that have a benefit on the colour depth/resolutions @Amethyst1
I am going to have to look for a 30hz capable monitor that won't break the bank now.
 

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domii said:
Yes, here you go. I had a thread on macos9lives where I was cobbling some info together.

I have my 1.5GHz Mac mini G4 running overclocked at 1.8GHz nicely with the stock cooler.

But after a wild ebay shopping spree on cheap Motorola G4 cpu's I may attempt replacing the original 1.5 with the 1.67Ghz and going for 2GHz+. But I need to build up some confidence first : )

I also wonder, with the Mac Mini 1.5, it has 64gb of vram vs 32gb on the other mini's, would that have a benefit on the colour depth/resolutions @Amethyst1
I am going to have to look for a 30hz capable monitor that won't break the bank now.
Click to expand...
Thank you very much!! Internet is not like before! the information disappears and is forgotten when time passes, I went crazy looking for this table and all the photos were missing.

I also bought the G4 1.67MHz on ebay at a good price, but I don't know if I would be able to make the change, I don't have professional equipment, it could be a success or a catastrophe. I'll be watching to see your progress.
 
Hello everyone, and apologies in advance if this doesn't belong in this still active thread, but I was curious if you all think whether this BGA replacement method for the iMac G4 could be applied to the PowerMac G3/G4 ZIF CPU boards?

I had been playing around with the idea of replacing the chip on a Yikes CPU (based on how older Sonnet cards got upgraded to higher speeds), but very little documentation is available for the circuit and resistors. The number of solder points is the same (360 pins) but I know that doesn't necessarily translate to the same layout.

Likely will still pursue it for science since the parts are relatively inexpensive (and also have some spare iMac G4 boards for parts), but any thoughts are appreciated before going down the rabbit hole!
 
I am a huge fan of the G4. It was my first computer (in 2016) and I used it for school work religiously until it died, sometime in 2019. It was the 700 MHz version if I remember correctly, and I sadly did not keep it. I recently picked up a 1GHz G4 that has intermittent issues. I've replaced RAM, to no avail. Is it possible that having this service done would help resolve my issues? I believe the processor is on the fritz, but it does boot (and then will randomly crash). Unfortunately, my expertise lies primarily in Radio and Television repair, and I am simply incapable of BGA soldering.
 
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