PowerMac G4 Dual CPU Question

I've changed my mind back to the PowerMac G4 that I found, yet again. Anyways, the PowerMac G4 I'm getting is an MDD model and I'm aware that they have dual CPU capabilities.

What I want to know is, is there two CPU slots inside the computer for additional CPU's or do you have to swap the Daughtercard with a different one? Of course I'd have to get the same CPU as the first CPU (Which in this one I'm getting has a 1.25GHz PowerPC G4) but then again, I'm still not sure if I can just plop the new CPU in place as easily as most PC systems are. I haven't gotten the PowerMac G4 quite yet, but I'll be getting it soon.

666sheep said:

FW800 (doesn't boot OS 9) vs. FW400 (does boot OS 9):

Single CPU card vs. Dual CPU card:

133 MHz bus CPU daughtercards: 867 DP, 1.0 SP

167 MHz bus CPU daughtercards: 1.0 DP, 1.25 SP, 1.25 DP, 1.42 DP

SP and DP ones are interchangeable (without a hassle), only bus speed must match. Otherwise it will need be adjusted using soldering iron If you're swapping SP with DP, get proper heatsink for DP.

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Ah, thank you. I wasn't expecting a post like this, but now that I've gotten it, I'm glad for it. This helped tons. Thanks!

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666sheep said:

133 MHz bus CPU daughtercards: 867 DP, 1.0 SP

167 MHz bus CPU daughtercards: 1.0 DP, 1.25 SP, 1.25 DP, 1.42 DP

SP and DP ones are interchangeable (without a hassle), only bus speed must match. Otherwise it will need be adjusted using soldering iron If you're swapping SP with DP, get proper heatsink for DP.

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And, just a question. Which Bus speeds have to match? I've never worked on an Apple computer before, as you might be able to tell. I know now that the first Bus Speed that needs to be matched is the Daughtercard speed. But I do not know what the second speed is that needs to be matched. Or is it if I swap a 167MHz Daughtercard the new one also has to be 167MHz? I only just realized after I started typing this last sentence

Intell said:

There is one connector for one G4 daughtercard. To upgrade to a dual G4, you must remove the single G4. Remember, the G4 you use to upgrade it with must be another MDD G4 or a MDD G4 compatible one.

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Okay, just a question:

Can the CPU be removed from the socket without soldering?

666sheep said:

Basically this. There's a way to alter bus speed on logic board and daughtercard (and CPU multiplier) but it requires soldering one or more tiny SMD resistors.

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Alright, but just buying another 167MHz Daughtercard won't be a problem? Because I won't solder anything of course because I have no experience with doing so. I wish it was as easy as doing it on a PC, just going into the BIOS and changing numbers.

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Intell said:

Yes, it comes right out like most standard socketed CPUs. Removed from the daughter card, no.

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I'm confused when you say the CPU comes out of the socket but then you say Removed from the Daughtercard...

Intell said:

The CPU is soldered onto the daughtercard and cannot be removed from it. To upgrade a G4 CPU, you remove the daughtercard from the socket that has the old CPU soldered on it. Then you put another daughtercard into the socket with the new CPU soldered on it. Reapply thermal paste and start the machine.

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Oh I see now, thanks for clearing that up. And, for a Dual-CPU setup, don't you need a heatsink that is bigger than the Single-CPU heatsink? I'm just asking this question because the PowerMac G4 MDD model I'm getting has only one 1.25GHz PowerPC G4, but then again, I'm not sure.

And, the RAM for these machines needs to be Non-ECC, Unbuffered, and Low-Density, correct? And it will take PC2700 the most powerful? And the RAM for the PowerMac G4 is 184 Pin, right?

Sorry I'm bombarding you with questions. I just don't know much about Apple computers, especially their PowerPC ones.

Intell said:

The dual MDD have a larger copper heat sink. The alumimum you have may not be enough and could lead to overheating. You can put PC2700 184 pin non-ECC low density ram in it. It may not run at 167Mhz, but it will work.

Note: A MDD single to dual conversion may not work. The single G4 has a fbus speed of 133Mhz just like the stock PC2100 ram. Putting in a dual G4, which only come in a 167Mhz with the exception of the 867 MHz dual, will require you to upgrade all of the ram to PC2700 to match the faster fbus speed. You'll also have to hope that the logicboard will speed up as well. It may automatically, it may require a resistor to be moved via soldering, it may just simply refuse to boot at all. Also remember only G4 CPUs from or designed for MDD G4's will work in your machine. I suggest you do some more research into MDD single to dual conversions.

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Oh...I had no idea how dangerous this could be! I was planning on buying four 512MB RAM modules of the above mentioned kind (PC2700) which I would use to upgrade to 2GB. The particular model I am buying only has 256MB of RAM. So getting the RAM would be the first thing I do since I want to upgrade the operating system to Mac OS X 10.5 Leopard.

I do indeed intend on doing research on upgrading to a Dual-CPU setup. I'm just hoping that this MDD I'm buying has two CPU's already because I am not in any position to do any soldering. I'd have to get someone to do it for me.

Theoretically, if I were to buy a Dual-CPU Daughtercard (Two PowerPC G4 1.25GHz) and the machine didn't boot, would I be able to just re-insert the old Daughtercard and the machine would be able to boot normally again? I fear permanently damaging the machine to the point where I'd have to buy a new logic board or a whole new machine.

And just a question: Would the performance of two PowerPC G4 1.25GHz equal the performance of my main computer's AMD Athlon X2 Dual Core (Which was originally clocked at 2.11GHz but now sits at 2.80GHz) or would it be a little less?

Intell said:

There is nothing to solder when upgrading a G4 CPU. Nothing.

If it doesn't boot with a dual G4, just put the old one back in and it'll work like nothing happened. You AMD machine will likely be faster for most tasks than any G4.

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Okay, I think this thread might be almost done, I'm getting answers I need, so thanks.

Just one more question!

Is there any possible way to get the MDD to boot with a Dual-CPU setup if it doesn't boot the first time?

Intell said:

The problem would be the fbus speed. To change this, you'll have to move a few resistors on the daughtercard or the logicboard so that they run at the same fbus speed. To, move them you'll have to solder them.

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Well, we'll see what happens. Thanks!