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G5 Quad - 32GB possible?

Joshuarocks

Joshuarocks

macrumors 6502
Original poster
Mar 12, 2011
364
1
Somewhere in Cyberspace
Oh, I saw on OWC's page under memory where there are "4GB DDR2 PC2-4200 dimms" for sale and was wondering if I were to get eight of those, would the machine go beyond 16GB like the 2006 mac pros after it? Remember the 2006 mac pros had a max of 16GB of memory according to Apple. But, OWC saw it could take up to 32GB?

Can the same be said about the G5 Quad and dual core machines?

Also, has anyone figured out a way to go beyond 2GB on say a PowerBook G4 Hi-res model or even a MDD G4 1.25 or 1.42? I read somewhere that the G4 can address over 2GB of memory, but Apple did something to the firmware to cripple it so it would only go up to 2GB.

Anyone??
 
The G5 supports 4GB modules.

G4 models cannot physically address more than 2GB total.
 
There have really only been a handful of macs that can go beyond their max. RAM spec. These are some that have not been limited by the onboard limit but rather the current available memory dimm sizes when the system came out. Most though are limited to what the max is listed as because it's a limitation in the logic board regardless of what size dimms you have.

Most of the Macs that can go higher than spec are Intel powered. The only PowerPC Mac I can recall going above spec is the eMac USB 2.0 model and some iMac G3's
 
300D said:
G4 models cannot physically address more than 2GB total.
Click to expand...

That is true for the Sawtooth, Gigabit Ethernet and MDD. The Digital Audio and Quicksilver can only hold 1.5GB. The Yikes G4 can only hold 1GB.

I will never understand in a million years why Apple allowed a 2GB limit in the first 2 G4 towers with AGP and then limited the next 2 models to 1.5GB. This is the main reason I run a Sawtooth. In my experience the extra 512MB (which is 33% more) outweighs any advantage the slightly faster bus offers.
 
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NZed said:
Wikipedia says 16gb so i guess 16gb only

btw why hasnt the above comments answer the OP's question??? or am i missing something here?
Click to expand...

Well if its on wikipedia...lol


And my guess is not many people have put that much ram in a g5.
 
zen.state said:
I will never understand in a million years why Apple allowed a 2GB limit in the first 2 G4 towers with AGP and then limited the next 2 models to 1.5GB.
Click to expand...

Until 5 years ago, 2GB was a LOT of memory. That much memory back in 2000 would have been almost $500.

These days, I can't imagine living without my 6.2GB ram disk. :D
 
300D said:
Until 5 years ago, 2GB was a LOT of memory. That much memory back in 2000 would have been almost $500.

These days, I can't imagine living without my 6.2GB ram disk. :D
Click to expand...

You have a point but any new models should not downgrade the expansion of the previous. They obviously realized 2GB should be allowed again for the MDD.

True about the RAM prices then. I remember paying about 180 for a 64MB dimm for my new B&W G3 is 1999. A friend of mine bought 16MB for his performa 6200 in 96 and paid about 1400.
 
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NZed said:
found a more reliable source

http://www.apple.com/pr/library/2005/oct/19pmg5.html

;):rolleyes:

not many people but "what if" the OP has many old RAMs lying around unused in mint condition? its worth it isnt?
Click to expand...

Of course its worth if the op has the ram. Its even worth it to buy it if its worth it to him. Im just saying theres not many people who have tried to put that much ram in their machine, so no one can say yeah I have 32gb in my rig right now. I doubt theres more than a couple users on here with 16gb of ram in their machine.
 
jchase2057 said:
Of course its worth if the op has the ram. Its even worth it to buy it if its worth it to him. Im just saying theres not many people who have tried to put that much ram in their machine, so no one can say yeah I have 32gb in my rig right now. I doubt theres more than a couple users on here with 16gb of ram in their machine.
Click to expand...

true

16gb DDR3 for MBP today cost about 1600 USD

so probably $800+ for DDR2??
 
Ok, I contacted OWC and wouldn't you know it - they have a G5 dual core machine as a test machine.. I asked the tech to put in 8x4GB PC2-4200 DDR2 memory and he will let me know if the memory controller can see past 16GB.

Remember, the G5 is a 64-bit processor unlike the G4 which is 32-bit.. so my guess is that if Leopard truly supports 64-bit, then the G5 should be able to recognize past 16GB. We will wait and see.. I am not interested in going that high, but just curious.
 
Joshuarocks said:
Remember, the G5 is a 64-bit processor unlike the G4 which is 32-bit.. so my guess is that if Leopard truly supports 64-bit, then the G5 should be able to recognize past 16GB. We will wait and see.. I am not interested in going that high, but just curious.
Click to expand...

A CPU being 32 or 64 bit has nothing to do with logic board limitations.
 
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Joshuarocks said:
Ok, I contacted OWC and wouldn't you know it - they have a G5 dual core machine as a test machine.. I asked the tech to put in 8x4GB PC2-4200 DDR2 memory and he will let me know if the memory controller can see past 16GB.
Click to expand...

Could you please post a link to those single 4GB PC2 4200 sticks? I cannot find them on OWC site, all of I've seen are 4GB kits (2x2GB).
 
zen.state said:
A CPU being 32 or 64 bit has nothing to do with logic board limitations.
Click to expand...

I was thinking of the 2009/2010 mac pros when one goes beyond 32GB, they can then enter 64-bit mode fully - meaning, the computer would then run in 64-bit mode.. something like that.

I know the CPU being 32 or 64 has nothing to do with the logic board limitations, but in order to access above 32GB say on a mac pro, you need to run in 64 bit mode.. I was thinking the same for the PM G5 Quad above 16GB of memory.
 
Joshuarocks said:
I was thinking of the 2009/2010 mac pros when one goes beyond 32GB, they can then enter 64-bit mode fully - meaning, the computer would then run in 64-bit mode.. something like that.

I know the CPU being 32 or 64 has nothing to do with the logic board limitations, but in order to access above 32GB say on a mac pro, you need to run in 64 bit mode.. I was thinking the same for the PM G5 Quad above 16GB of memory.
Click to expand...

You should never expect x86/CISC results from PowerPC/RISC architectures of any form. I'm sure you don't expect an apple to taste like an orange right? :)
 
I'm fairly certain that although the machine would recognize that much RAM, but I don't think that Leopard would be able to address that much RAM since I seem to recall there being limitations of some sort since it's still a 32-bit kernel.

In any case, it looks like it would cost about $1200 to figure it out for sure. Anyone up for that? I'm going to go out on a limb and say that this is nothing more than a matter of intellectual curiosity.
 
Joshuarocks said:
I was thinking of the 2009/2010 mac pros when one goes beyond 32GB, they can then enter 64-bit mode fully - meaning, the computer would then run in 64-bit mode.. something like that.
Click to expand...

ALL 2009/2010 Mac Pros support a 64bit Kernel (the 2010 already comes with 64bit enabled), the OS, however is always 64bit, no matter whether you run a 32 or 64bit Kernel. (In fact the 32bit Kernel is a 36bit one (PAE)).

Anyhow, everything beyond 32GB RAM requires a 64bit kernel (due to the limitation of the 32 + 4 Kernel (36bit), which happens to be 32GB in Apples machines).

Since the Powermac doesn't have a 64bit Kernel, the machine would theoretically be limited to 32GB (which is also usable by Leopard).
 
Transporteur said:
(In fact the 32bit Kernel is a 36bit one (PAE)).
Click to expand...

True for Intel versions of 10.5 and OFC 10.6. But how it is with PPC? AFAIK PAE isn't supported in PPC 10.5 kernel because it's x86 feature.

BTW, thread becomes more and more interesting :)

I've found something what confused me a little:

http://discussions.info.apple.com/thread.jspa?messageID=11230112&#11230112

Since Leopard is 32-bit it can address up to 4 GBs per processor. For Core 2 Duo machines the maximum is, therefore, 8 GBs. For 4-core machines it's 16 GBs, and for 8-core machines it's 32 GBs.
Click to expand...

Could someone shed some light on this statement? Is it wrong or right?
What about 32GB in MP 1.1 then? (it works, as all of you know, but according to above quotation it shouldn't).
 
666sheep said:
True for Intel versions of 10.5 and OFC 10.6. But how it is with PPC? AFAIK PAE isn't supported in PPC 10.5 kernel because it's x86 feature.
Click to expand...

Has to be. A 32bit Kernel would limit the RAM to 4GB, yet the PowerMac G5 is advertised to work with up to 16GB of RAM (which it does).

I don't know of any other technology that would make a 32bit Kernel address more than 4GB.
 
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666sheep said:
"Since Leopard is 32-bit it can address up to 4 GBs per processor. For Core 2 Duo machines the maximum is, therefore, 8 GBs. For 4-core machines it's 16 GBs, and for 8-core machines it's 32 GBs."

Could someone shed some light on this statement? Is it wrong or right?
What about 32GB in MP 1.1 then? (it works, as all of you know, but according to above quotation it shouldn't).
Click to expand...

This page has some very good and clear info on exactly what bit which architectures run at under 10.5

Based on what it says Leo IS true 64 bit all the way through on x86 and PowerPC. Tiger was even 64 bit at the Darwin level.
 
zen.state said:
This page has some very good and clear info on exactly what bit which architectures run at under 10.5

Based on what it says Leo IS true 64 bit all the way through on x86 and PowerPC. Tiger was even 64 bit at the Darwin level.
Click to expand...

That was the link I was looking for but couldn't find. This confirms some of what I thought, but not all of it. I'm still curious as to whether or not the RAM address in Leopard would be big enough for the kernel to address more than 16GB of RAM, which I believe is the limit of the 48-bit(?) addressing scheme that OS X used with the 32 bit kernel, IIRC. I knew better once upon a time, but in 2004-5, it didn't seem like it would ever matter before those machines went belly up.
 
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