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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > Upgrading a Powermac

Upgrading a Powermac
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cman8
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Mar 20, 2006, 12:49 AM
 
Quick question, If I buy a powermac g5 1.6 ghz single, can I upgrade it to a dual by just buying nother processor in the future?
     
jamil5454
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Mar 20, 2006, 01:14 AM
 
Nope. PowerMac G5s aren't upgradeable AFAIK.
     
Krauti
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Mar 20, 2006, 07:14 AM
 
The 1.6 certainly not, because it had a different motherboard, but what exactly was so difficult to upgrade in the real G5s? The CPU is on a daughter card, if I'm not mistaken. Why isn't it replacable, or is it just that nobody ever tried?
     
OreoCookie
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Mar 20, 2006, 07:46 AM
 
Practically, you cannot get cpus other than as spare parts by Apple. I'm not aware any of the usual suspects plans to release upgrade cards for G5s. Theoretically, I think a G5 shouldn't be hard to upgrade … 

Also, the 1.6 GHz G5 has only one cpu socket (he has the pins for a second, but the socket itself is missing).
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jamil5454
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Mar 20, 2006, 10:57 AM
 
From what I've heard, the G5 logic board only accepts the same speed G5 that shipped with it. If you were to put in a higher clocked G5, the computer wouldn't boot. There's probably a way to overcome this, but Apple has locked down the PowerMac G5s pretty well so far.
     
OreoCookie
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Mar 20, 2006, 12:16 PM
 
AFAIK nobody has been able to overclock a PowerMac G5 yet. The cpu runs at a fixed ratio with respect to the bus speed -- in most PowerMacs the bus is running at half the cpu speed (there are a few exceptions, some of the small models' bus ran at one third of the cpu speed).
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Lateralus
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Mar 20, 2006, 02:19 PM
 
From what I can tell, the determing factor in dropping in a faster processor is the bus speed and not the clock speed. Dropping a 1.8GHz G5 from a system with a 900MHz bus into the 1.6GHz G5, which has an 800MHz bus, doesn't work because the 1.8GHz CPU is tailored for a 900MHz system.

The G5 does, however, support clock multipliers beyond 2x, up to 6x I believe. So in the future, as faster G5s become available, I think we'll see G5 processor upgrades through the use of the higher multipliers.

FYI: I have heard more than once that Apple used the Rev B 2.5GHz/AGP motherboard as the test bed for the 2.5GHz 970MP CPUs currently shipping in the Quad. That would corroborate the fact that any issues involved with CPU swapping are in fact because of the bus speed.
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cman8  (op)
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Mar 22, 2006, 04:37 AM
 
Great thanks for your help i just wanted to know if I should just keep saving to get a dual or buy a single now for cheaper.
Thanks again.
     
Todd Madson
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Mar 22, 2006, 11:27 AM
 
If you're going to spend the money for a G5, getting a dual will get you
better performance overall than a single.

Secondly, remember that increasing the clock speed of a G5 brings into
play all kinds of potential issues, mainly thermal.

People not familiar with them don't realize that although they are quiet,
they generate prodigious amount of heat and use a lot of electricity.

Overclocking one would potentially be dangerous just from the heat
standpoint - my DP 2.5 at full load can generate unbelievable temperatures
at the backside of the memory controller, exceeding 210 degrees
fahrenheit.

You might want to consider purchasing a refurbished faster machine:
Currently on the Apple online Store refurb single 1.8s are $1099
with the duals being $1299. A dual 2.0 is $1499. But a refurbished
dual core 2.0 is $1699 and that might be a good machine to get because
of the PCI Express bus, faster memory and larger caches on the CPU.
Dual 2.3 dual cores are right at $1999 now. Dual 2.5s are $2049 and
dual 2.7s are $2149. You can even get a quad for $2799.

Looking at those selections, I think the best deal is the refurbished
dual core 2.0 - if you can hold out a little longer the 2.3 might be the
real best bet. It's the fastest non-liquid-cooled system they've got
and reports are that it runs Seti @ Home faster than any other system
out there besides the quad.
     
mountainash
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Mar 24, 2006, 10:28 AM
 
Ok, the logic boards for dual and single CPU G5s are different. Each CPU is it's own module, and the single CPU logic board only has a connector for 1 CPU module. It sucks, but it makes sense. Also, I believe that the FSB is set on the logic board (this shouldn't be too hard to hack). This means the system bus is fixed. Also your single CPU G5 only has 4 ram slots (instead of 8 on the dual models).

If you open up your G5, you will see all the blank space where the extra components go in dual G5s.

If you are lucky, a third party might make an upgrade (maybe even a dual core). But for now, the only way to safely speed the CPU or go dual is to get a whole new machine
Power Mac G4 Digital Audio 533MHz 1.5GiB RAM, 2x 80Gb ATA HDDs, 320Gb SATA HDD, Radeon 9650 256MiB, Airport Extreme compatible PCI card, Zip 250, Pioneer 110, Firewire DVD burner, 21" CRT, Harmon Kardon Apple Pro Speakers, OS X 10.4.6
Powerbook Pismo G3 400MHz, 768MiB RAM, 80Gb HDD, AirPort Extreme PC Card, Bluetooth 1.1, DVD-ROM, OS X 10.4.6, Ubuntu 5.10, MacOS 9.2.2
To buy: RAM for Pismo, CPU upgrades
     
   
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