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

[asaggynoodle]

I've done this about a dozen times, still trying to perfect this operation though (About ~40% success rate).

What temperature/equipment do you use to clean the pads after you remove the CPU? My boards almost ALWAYS lose a pad or two after cleaning them off with my Hakko and solder wick.

Also, what size balls do you use on your replacement chips? I've been using .76MM lead balls, but I feel they are too big. I can't find any way to get the suggested ones in the Datasheet.

 

[max1zzz]

I use my aoyue 936 soldering iron with a blade type tip to remove most of the solder, just apply a little leaded solder to the tip and wipe it across the pads (if you have a proper ir bottom heater do this with the board still on the heater and it's way easier). Then I switch the tip to a normal pointed type and use desoldering braid to remove anything remaining (get good quality chemtronics braid and not the cheap stuff). If there is anything left I use some very very fine grain sandpaper to remove anything remaining. I had my iron set pretty hot, around 400C, I would have gone a bit cooler if the board was on a prehaeter.

I haven't been reballing the chips, mine came from china with balls attached. However from what I have read on the datasheets they should be 0.89mm, I haven't been able to find any solder balls or stencils of this size though. I'm pretty sure my chips from china have .76mm balls as they sit a little lower than the original.

 

[asaggynoodle]

Thank you so much for posting that, the only reason I've to reball my chips is because finding them new is usually about the cost of the actual upgrade card for retail price.

I managed to find a Soldering stencil on eBay that worked pretty well, I'd say 90% accuracy. It came in a kit with about ~20 different stencils. The stencil itself is about 2x the surface area of the chip, so actually applying the balls is a major PITA even with a holder. 

 

[max1zzz]

Are you using direct heat stencils or not? I have tried reballing xbox chips with them before and found it quite easy, but the stencils always stuck to the chip and where a right pain to get off again. I then tried with the better quality non direct heat ones and could never get them to work, I either knocked the balls off center removing the stencil, or they moved when I started heating

 

[asaggynoodle]

Yep, the direct heat ones. I've had ALL of the problems you've mentioned. 
I always have to put them between two slices of wood and try to crush them so they flatten back out after ripping the chip out. 

You can see the lot of them I got, and the one I use for PPC stuff. The Flux outline on the stencil shows how small the chip is. 

Spoiler

 

[Daniël]

Pretty interesting to see this, as this is an idea I've had going for a while, after being told the 7410 is pincompatible with the 750. I've always wanted to try it and this convinced me I can do it, as the way you're doing it is exactly how I envision doing it. Though I really want to try it on a slotloading iMac, which is probably going to be a bit more complicated. But nothing a bit of Kapton tape can't fix, right?   

 

[max1zzz]

It should work on a slotloading iMac just fine, I was planning to try this on a iBook G3 (Dual USB) for no reason other than I have one spare and it should work

 

[Gorgonops]

Hrm. Are you sure you can do it to a "dual usb" iBook? A quick Google claims that uses the 750CX with built-in cache, is that still the same pinout?

 

[LightBulbFun]

Just signed up to say what an awesome project this is turning out to be (some of you might recognise me from Mac rumors I hang around the PowerPC section). like Dan above. I have been looking into doing something like this and its awesome to see that it works. I know of one other person who did this with a G3 Pismo card. Just a couple notes that might help. on Gossamer machines (G3 Beige tray load iMac etc) the L2 cache is indeed tied to the CPUs multiplier so you can end up limited by how fast you can clock due to the L2 cache. and also G4 chips can run a bit hotter then the same clocked G3 chip so keep that in mind you might want to add on some extra cooling. anyway I have been wondering if you could also turn G3 ZIF CPUs into G4s that and try a slot loading iMac like dan (ones with normal 750s should work) also the first gen clamshell used a 750 so that might even work. (but all the iBooks ahead of it used 750CXs and up which are not pin compatible with a 7400/7410) one of the Main reasons I wanna do all of this is Just to run leopard on these machines (that and its such a cool thing to do)

so yeah Awesome work guys cant wait to see what happens next

 

[max1zzz]

Hrm. Are you sure you can do it to a "dual usb" iBook? A quick Google claims that uses the 750CX with built-in cache, is that still the same pinout?

I never even considered that, and the answer is no, it's a completely different package so it wouldn't work

Edit: Looks like LightBulbFun beat me to it

Anyhow, my next step with this is going to be to try modifying a second card and swapping the cache chips for faster ones an seeinf if I can clock the chip all the way up

 

[LightBulbFun]

one more thing I should mention is that I have found that when you Put G4 CPUs into G3 Gossamer systems (Say a G4 ZIF from a Yikes into a G3 Beige) sometimes the L2 cache will not show up unless you install an enabler so when doing this iMac tray loader modding if you do not see L2 cache try installing an enabler and running before and after benchmarks to see if the L2 cache is actually being used 

 

[CC_333]

Doing this to a clamshell iBook is a neat idea! I have a spare 300 MHz non-Firewire board I can contribute if anyone wants to experiment with it?

The charging circuitry's seemingly bad (it won't recognize any battery I throw at it), but it works fine otherwise.
 

I also have a 366 Firewire board, but it has a bad inverter connector (it literally fell off; the circuit itself, however, should still be working), so testing it would be somewhat difficult unless one jury rigs an external power source for the LCD backlight (or repairs that connector).

c

 

[belgaonkar]

Doing this to a clamshell iBook is a neat idea! I have a spare 300 MHz non-Firewire board I can contribute if anyone wants to experiment with it?

I can donate a fully working iBook so you don't have to worry about the battery issue.

 

[LightBulbFun]

Just want to mentioned that I ordered a bunch of soldering tools and a lot of 5 7410s on ebay so I will be attempting this my self (well not a tray loading iMac ill start with a 300Mhz G3 ZIF from my G3 BW beater) got the soldering tools from sellers in the UK but the 7410s are on a slow boat from china LOL... (5 for  £50~ aint too bad tho) if the G3 ZIF swap works next thing ill try is a G3 Pismo I have (I do have  a Slot loading iMac with a regular 750 but ill have to think about that as Flower Power iMacs dont grow on trees ) btw Max1zzz when you put the 7410 on if you used any flux how did you apply it and how much did you use? just wondering heh (and if there is anything else I should be aware of when I do this. I have a fairly good grasp in whats involved but i wanna make sure everything goes to plan and i dont end up nuking a Mac or 2 )

 

[max1zzz]

You need flux, if you don't you'll have a really hard time getting it to work. Get yourself a bottle of insat RMA off of ebay, it's about £13 for a 50ml bottle but it's really good stuff. Flood the array before lifting the old chip, then when you are fitting the new chip put a drop of it in the middle of the array and spread it all over it (When i say a drop i mean a drop) then put a small amount of flux paste over this.

My next step on this is to try it on a clamshell, belgaonkar have very kindly sent me a hole clamshell as well as a second logicboard (which I will fit a G4 onto and send back to him). One day i will get back to working on the trayloading imac. Kinda lost interest on it after I killed the card....

 

[LightBulbFun]

ah very cool thanks for the reply this is the Flux I ordered http://www.ebay.co.uk/itm/MG-Chemicals-Liquid-Rosin-Flux-835-P-Pensize-/322315289765?hash=item4b0b7d04a5:g:MkAAAOSwrklVOrHt(I knew you needed flux but i wanted some input on someone who has done it before ) but yeah thanks for the advice ill keep it in mind when i do mine. Also good luck on the clamshell make sure to keep us updated also keep in mind that 7410s can run a little hotter then G3s (tho they are not as bad as 7400s where) but I suspect if your keeping it at 300Mhz then a 500Mhz 7410 at that speed should run nice and cool I just recently bagged a 500Mhz G4 Sonnet that has a 450Mhz 7410 on it runs nicely in my G3 BW (im using a custom Leo install I made as stock leo does not have any drivers for Gossamer and older macs)

 

[max1zzz]

you will need some actual liquid flux for when you lift the old chip off the board, this is what I use: http://www.ebay.co.uk/itm/230729054223

 

[LightBulbFun]

alright cool. hope you dont mind the questions but what temp and airflow settings did you use to Remove the 750 G3 from the board? I have not done this sort of thing before so trying to get as much info as I can on it

 

[max1zzz]

What kit do you have exactly? I slowly rampd the temperature up to about 210C  on the top heater (which is lower than the melting point of the solder, but the gap is made up for by the bottom heater)

 

[LightBulbFun]

I have a 858D hot air gun/rework station. I dont have a bottom heater like you tho...  (I also have a 936D digital Hakko clone soldering iron) I have a few Scarp boards (inc a dead MBP3,1 Logicboard) that ill practice removing parts off of as well thanks for the help btw I do appreciate it a lot