iMac G3 (Rev A -> C) G4 CPU Upgrade

[max1zzz]

It's been a long time coming, But I finally gave this a stab today

I started by removing the old CPU from the card (anyone who dose BGA rework professionally might want to look away, my setup isn't exactly pretty....)

A overview of the setup, I'm using a griddle as a preheater and a attan 858D as a top heater. It's cheap but it works

A close up of the action

Phew, Got the chip off without lifting any pads

The "Victim" - One now unneeded Power PC 750

The pads cleaned up nicely, Almost ready for a new CPU

Not content with the slightly dodgy method of removing the old CPU, I select my "Weapon" for resoldering. 1600w of uncontrolled heat should do nicley

New chip lined up, Also added a little shielding to stop the ram slot melting.

One minute thirty seconds later we now have one Power PC 7410 firmly attached to the board.

It lives!!!

Mac OS 8.6 doesn't quite know what to make of the Chip, I guess nothing that supports 8.6 ever shipped with a Power PC 7410

 

[max1zzz]

Mac OS 9.2.2 However knows exactly what it is

I still need to fiddle with the multiplier jumpers, the chip is a 500mhz part should I should be able to clock it up at least that fast.

Now, I ordered 3 chips, Assuming I would screw it up at least once.... What should be next to go under the knife for a G4 upgrade?

 

[CC_333]

Ooooo!! Once you perfect your technique, I'd be interested in possibly having you upgrade one of my CPU boards!

Alternatively, I can donate one from my Rev. A/B (not sure which, but it's definitely not a Rev. C or D) in the name of science, and if you're successful in upgrading it I'll pay you for your work and you can send it back.

Whatever you want to do....

c

 

[max1zzz]

If your interested in one we could do a card swap, i'll upgrade on of my spares and swap if for your unupgraded one

It's actually a surprisingly simple process once you get the hang of it, I actually think BGA chips are quite a lot easier to solder then things like high pin count TQFP chips (But then I used to do this allot with xbox 360's so I do have a fair bit of experience with it)

I do need to see how it fares heat wise though, the 7410 is the lower power version of the 7400 iirc (at least it was the one apple used in there laptop's) So it should be ok, but the iMac dosen't have the biggest heatsink in the world

 

[Compgeke]

Now, I ordered 3 chips, Assuming I would screw it up at least once.... What should be next to go under the knife for a G4 upgrade?

A G3 ZIF CPU card would be fun if possible, those can be throw in both G3s and ZIF carrier upgrades for double usefulness.

 

[max1zzz]

ZIF cards should be fairly easy, i'll have to have a look and see if my G3 DT still has it's CPU card in it (My B&W has a sonnet G4 card in it sh there wouldn't be much point in upgrading that )

 

[MidnightCommando]

Would the same principle work for replacing BGA 603ev with PPC 740? I investigated this as a possible upgrade route for the 6500 and 1400c a while back, but never got my 740 ICs...

 

[IPalindromeI]

It'd need to be pin compatible, probably software compatible as well - firmware especially counts. The G4 seems to be a drop-in replacement, seeing as it's basically just a G3 with SIMD.

 

[MidnightCommando]

The 740 is pin- and code- compatible with the 603ev; the 750 (the G3 that Apple shipped in things) isn't... the 750 has on-die cache.

A 740 should still whip a 603 cycle-for-cycle though.

Can't find any places to source a PPC740L-GB366 though...

 

[max1zzz]

Would be interesting to try, I can find them, but only in a BGA package and as far as I am aware no macs ever used the 603 in a BGA package

 

[CC_333]

If your interested in one we could do a card swap, i'll upgrade on of my spares and swap if for your unupgraded one

Sure! That can work.

I will try to dig it out. By chance, have you been able to up-clock the CPU board so the G4 chip runs at its rated speed of 500 MHz?

c

 

[max1zzz]

Haven't had a chance yet, Will probably have a go tomorrow after work

 

[Bunsen]

as far as I am aware no macs ever used the 603 in a BGA package

1400, 2300, 5300?

 

[max1zzz]

Ahh, ok, I didn't know that. This may be of interest then: https://www.aliexpress.com/item/PPC740L-GB500A2-PPC740L/32321945368.htmlNot exactly cheap though

I have also tried clocking up the G4, with mixed results... 500mhz and 466mhz produced nothing, the iMac didn't boot at all. I then tried 400mhz (skipping 433mhz) which worked fine. There are three reasons I can think of the it didn't work, It may be the iMac simply won't support a CPU at that speed for some reason, it my be my soldering was a bit dodgy, or it could be that the chips I brought from china are not what they claim to be and are actually a slower version of the chip (Although I think this is unlikely). Either way I'll do some more experimenting over the next few days

 

[MidnightCommando]

603ev in BGA package is found in: 6500/225 and faster, 1400/166, 3400c. Any of which would benefit from affordable G3 upgradeability these days, let's be real.

 

[rsolberg]

A PPC740 upgraded 6500 logic board could be an interesting upgrade path for a TAM. Comparing the datasheets for the 250-300MHz BGA 603e and the 500MHz 740L, I noticed that the 603e needs a VCore of 2.6v, vs 2.0v for the 740L. That would have to be addressed, as 2.6v is well beyond the maximum tolerance of the 740L.

As for the iMac upgrade, it appears the 7410 has a recommended VCore of 1.8v. Perhaps the VCore supply is too high for stable operation above 400MHz and a voltage regulation modification is necessary?

 

[max1zzz]

hmm, that sounds likely, it did seem to be getting very hot above 400mhz. I'm not sure how I would go about modifying the VCore voltage though

 

[MidnightCommando]

Let me look at the 6500 board I have here to see if I can identify the power circuitry - I have a sneaking suspicion it's using a normal off-the-shelf voltage regulator which could be adjusted with trivial effort, from memory. 

 

[waynestewart]

Been a while but I thought the iMac processor card had cache chips on it. If so, wouldn't that be limiting the speed?