Does OSX leopard 10.5 have a 4GB limit?

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Level 1

21 points

Does OSX leopard 10.5 have a 4GB limit?

I have seen and read various things about OSX Leopard 10.5 only using 4GB and nothing above?

I'm still on Leopard 10.5.8 as my PT and plug ins all work ok..

I mainly use Logic, PT and Ableton with plugs like NI Kontakt 3 and East West Libraries etc

However when I bought my Mac Pro (early 2009) I was told to put as much RAM as I could (like most PC and Mac's) so I have 10Gb available

But if Leopard is limiting the RAM, surely 6GB of it is always sitting unused? Or is the 10Gb distributed evenly, like 4Gb for Ableton, and more (extra) memory for large plug ins? eventually using up the 10Gb til it falls over?

Will all my 10Gb be used or is 6GB of that just a waste in 10.5?

Mac Pro 10Gb * Macbook Pro 2Gb (late 2008), Mac OS X (10.5.5)

Posted on Mar 16, 2010 10:37 AM

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Answer 1

Mar 16, 2010 11:23 AM in response to pitchfork

Applications in OSX use the amount of RAM they need, up to a maximum of 4GB +for each application+ (assuming you have enough overall RAM): it's not like OS9 ad earlier where you could increase the amount of RAM used by a specific application. If you manage to use up all your overall RAM by opening a lot of RAM-hungry applications then it won't fall over, but as by then it will be using 'virtual memory' (transferring currently unused RAM to disk) you may see a slowdown.

I believe the maximimum total amount of RAM which can be addressed in Leopard is 32GB: I've seen it claimed that in Snow Leopard this is 16 terabytes, so start saving now...

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Answer 2

Kappy

Level 10

361,741 points

Mar 16, 2010 11:30 AM in response to Roger Wilmut1

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. Of course SL is 64-bit so the maximum is much greater. But from a purely practical point of view the limit is determined by the largest compatible RAM module and the number of RAM slots in the machine. The 8-core Mac Pros have 8 slots. The largest compatible module is currently 4 GBs, so those machines can install up to 32 GBs.

32-bit applications, however, are limited to addressing 4 GBs.

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Answer 3

Mar 16, 2010 3:55 PM in response to Kappy

Thanks for that, it's interesting to have the technical background.

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