G4 7448 and 7457 swap

[Jordy-G5]

Not sure if anybody still frequents this thread, but I have a 1.42GHz MDD G4, with a spare processor card. Since I have a couple SC7448 HX1700LD processors, I'm considering attempting a swap. The processors look to be new stock or very well pulled and reball'd because there's not a mark on the processors. Obviously I'd need to track down the CBGA adapters that I see are no longer sold. I really should have pulled the trigger them back in the day! I was moving around a lot a couple years back and didn't have time to tinker with this stuff.

The 1GHz spare processor card is rocking 7455's running @ 167MHz from what I can decipher from the resistors, so it would save me a little bit of time, obviously I'd have to move some resistors around for voltage.

My other thought was just to overclock the existing 1.42GHz board or try and find some 7457's and go that route for this machine and save the 7448's for my 15" DLSD 1.67GHz Powerbook, from what I read here it should have the bootrom to do a direct swap.

Any advice or words of wisdom?

 

[Matias_]

Whoa, where did you find those 7448 chips? They seem quite hard to find for a reasonable price, unless I'm looking in the wrong places. I'd also like to try and upgrade my 15" DLSD PBG4.

 

[Jordy-G5]

Whoa, where did you find those 7448 chips? They seem quite hard to find for a reasonable price, unless I'm looking in the wrong places. I'd also like to try and upgrade my 15" DLSD PBG4.

I picked them up probably 4 years ago now when they were a lot more for sale. There were definitely some sketchier listings at that time, some clearly had been pulled aggressively. I'm still not 100% certain they are legit or working but I'm fairly confident because of the die size and the etching all seems to line up, especially comparing 7447B I have there that I know are from a factory tray.

I also wonder if I should leave good alone. I bought almost all my systems news, didn't buy an Intel Mac new, just toyed around with a Mac Pro for a little while back in the day. Like I had mentioned, travelled a lot for work so they sit safely stored and once in a while I get the systems out for nostalgia.

 

[indibil]

Hello.

It seems the SWAP craze has waned a bit, but I've been playing for a couple of days with a G-Celerator and a 7457. I've unlocked a few achievements, though I suppose nothing groundbreaking.

Hope you enjoy it.

https://rosysumenteinquieta.blogspot.com/2026/03/vamos-divertirnos-con-un-giga-designs-g.html

 

[sailorMH]

Very nice, thank you for experience. My MDD still waiting for 2x 7457 ;-)
Vhat about CPU temperature with 1.45 VCore?

 

[indibil]

Very nice, thank you for experience. My MDD still waiting for 2x 7457 ;-)
Vhat about CPU temperature with 1.45 VCore?

Well, I can't tell you the exact temperature; I didn't measure it. But the heatsink is very small, and it didn't feel hot to the touch—almost body temperature.

I think if your MDD cools well with 2x7455 at 1.47GHz at 1.6v, it should be able to cool 2x7457 at 1.67GHz at 1.45v.

You should keep the cache ratio at 6:1 because your 300MHz chips will run at 278MHz at 1.67GHz. With a 5:1 cache ratio, they'll run at 334MHz, which is perhaps too much. It would be ideal to use a 5.5:1 ratio, but I don't know how to modify it in the EEPROM.

 

[sailorMH]

I make some Thermal ( in real electric Power ) graphs for replacement 7455 - 7457
Here is 7555A:

and here 7457:

You are right, original 7455 / 1400 MHz has max 39W, new 7457 / 1667 MHz will have max 36W

And L3 ratio I have already 1:6, so real freq. will be278 MHz, it is OK

 

[indibil]

I make some Thermal ( in real electric Power ) graphs for replacement 7455 - 7457
Here is 7555A:
View attachment 2611698

and here 7457:
View attachment 2611700
You are right, original 7455 / 1400 MHz has max 39W, new 7457 / 1667 MHz will have max 36W

And L3 ratio I have already 1:6, so real freq. will be278 MHz, it is OK

These figures are theoretical, right? I don't know if it takes into account the overvoltage of both models, but I don't think you'll have any problems at 1.67GHz. I think there's someone on the forum with a Dual 7455 OC at 1.6GHz who claims it's been working for a long time without issues.

I mentioned keeping the ratio at 6:1 because I told you a while ago that it could be lowered to 5:1. Remember that your chips are 300MHz; it would be good to see if they can handle 333MHz 🙂, although 278MHz would be more prudent.

From what you wrote, you have the MC7457s but you haven't done the swap yet, right? Were you able to test the Vcore at 1.4V? I have my original Dual 1.42 with the Vcore slightly lowered; it runs cooler and works the same. I hope you can swap them soon.

 

[sailorMH]

These figures are theoretical, right? I don't know if it takes into account the overvoltage of both models, but I don't think you'll have any problems at 1.67GHz. I think there's someone on the forum with a Dual 7455 OC at 1.6GHz who claims it's been working for a long time without issues.

I mentioned keeping the ratio at 6:1 because I told you a while ago that it could be lowered to 5:1. Remember that your chips are 300MHz; it would be good to see if they can handle 333MHz 🙂, although 278MHz would be more prudent.

From what you wrote, you have the MC7457s but you haven't done the swap yet, right? Were you able to test the Vcore at 1.4V? I have my original Dual 1.42 with the Vcore slightly lowered; it runs cooler and works the same. I hope you can swap them soon.

Graphs are theoretical. Square points are exact data from manual, line is extrapolation to high frequency.

About L3 frequency, I am not sure if I know howto change it to 1:5 :-(
I have 1:6 allready.

I just made cpu swap for 2x 7457 / 1666 MHz / 1.4 V. But not tested it yet - I now testing new powerpc board Mirari, so I will need a little time to return again to my Powermac G4.

 

[indibil]

Graphs are theoretical. Square points are exact data from manual, line is extrapolation to high frequency.

About L3 frequency, I am not sure if I know howto change it to 1:5 :-(
I have 1:6 allready.

I just made cpu swap for 2x 7457 / 1666 MHz / 1.4 V. But not tested it yet - I now testing new powerpc board Mirari, so I will need a little time to return again to my Powermac G4.

Very good! But you might need to adjust it to 1.45V to get a stable 1.67V. Let us know how it goes.

I'm not familiar with this Mirari board; is it for the Amiga?

 

[sailorMH]

Very good! But you might need to adjust it to 1.45V to get a stable 1.67V. Let us know how it goes.

I'm not familiar with this Mirari board; is it for the Amiga?

Yes, it is ppc board, compatible with AmigaOS, MorphOS and linux: https://mirari.vitasys.nl/
First model has T1042 CPU (4x e5500 cores ) at 1.4 / 1.6 GHz.
My fast speed check is here:
https://intuitionbase.com/articles/mirari-coming
( note: In last graph with GLQuake is very probably error - results seems capped to monitor frequency. But others are OK ).
Of course, Powermac G5 is still The King, but everything other is slower than Mirari.
Generally, it looks very promising. And if all will be OK, there will be version with T2081 CPU ( 4x e6500 core with AltiVec ) at 1.8 ( maybe 2.0 ) GHz. And this version should be on par with Quad or even faster. This core has two threads and is faster per MHz than G5.

 

[indibil]

Wow! That's exciting! I wish it would work with OSX, and even better, with OS9!

Congratulations on being able to enjoy these new "toys"!

 

[LightBulbFun]

Hello.

It seems the SWAP craze has waned a bit, but I've been playing for a couple of days with a G-Celerator and a 7457. I've unlocked a few achievements, though I suppose nothing groundbreaking.

Hope you enjoy it.

https://rosysumenteinquieta.blogspot.com/2026/03/vamos-divertirnos-con-un-giga-designs-g.html

View attachment 2611266

View attachment 2611265

Very cool stuff! makes me a bit nostalgic, the very first CPU Upgrade I ever got for my Sawtooth was one of those Giga-Designs G4's 🙂 it fittingly lives in one of @bunnspecial's Sawtooth's these days 🙂 I have often thought it would make a good candidate for being CPU swapped given its CPU multiplier and vCore Jumpers already present

 

[Jordy-G5]

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Recently acquired one of these. Got Kernel 6.12.20 running on it, basically the Mirari or what Power progress has been toying with on steroids. With a bit more spare time want to get a stable build environment so I can retire the poor G5 from compiling stuff. 12 x E6500, 24 threads @ 1.8GHz, 6 DDR3 ECC slots.

It's also compatible with Little endian but that's been a long struggle of recompiling stuff, most PPC64le distros compile for Power8 which has a few more instructions than this and you also lose Altivec on this processor when going little endian. I haven't reached out the to the MorphOS guys but there's probably no major reason that it wouldn't boot on this machine if it's booting on a T2080 compatible machine.

 

[sailorMH]

@Jordy-G5
it looks like very interesting machine! Unfortunately, the price is not so low to I have it only just for fun.
What distro do you have here? Some custom from NXP, or common distro like Debian?

 

[Jordy-G5]

@sailorMH
Yeah the price isn't amazing, for what they still sell for new it's a bargain, for me I knew I would really enjoy the project and I won't miss the money. I'm fortunate I know.

Currently running a Yocto build. Haven't had too much time to play around with it, I spent so much time this past weekend just setting up a Docker image on my build system just to get the Freescale stuff compiling. Probably next weekend I'll get another crack at figuring out why the Yocto build process keeps overwriting my kernel config and I'll post some pictures from X11 or Wayland of a desktop environment. It strips out my changes for Radeon or AMDGPU drivers when it compiles the kernel even following the tutorials. My next step might be to pull the kernel source with the patches out of the build Yocto build process and compile it with the configuration modified. I can revisit the pain of the Yocto build process later if I so desire. lol

It's not for the faint of heart! Once I have a kernel that tries to load the drivers I'll know what video card will work and I will probably install Debian or Archpower using that kernel.