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Upgrade allow more ram?


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#1
y0itsj0hn

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so my 2.13ghz intel imac, running tiger can support up to 3gb ram..

would upgrading to leopard / snow leopard allow me to use more ram?

#2
fleggyCakes

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Not likely, that 3gb limit is imposed by your chipset, not your OS

#3
Adrian Fogge

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FleggyCakes is right, no matter how much I truly wish that he was wrong and that Apple wouldn't have gone with a chipset with such idiotic artificial limitations and allow one to make use of however much memory you throw at the problem.

The whole idea of this 3GB limitation is idiotic and it really amounts to a design flaw on Intel's side that they decided to restrict rather than retool and remanufacture. Specifically, when you started to use more than 3.25 GB of memory using their chipset, it would start overlapping your memory assignments, thereby introducing *major* stability issues.

This is not a 32-bit limitation.

~Adrian

#4
xieqiao

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It has more to do with motherboard that must supports more than 3.25 GB rams. That said, 64-bit OSs including Vista 64-bit and Mac Leopard should support more than 3.25 GB rams.

#5
Adrian Fogge

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xieqiao, the chipset houses the memory controller... the memory controller is what determines the maximum amount of memory that is supported.

While it is *true* that the motherboard is an important piece in what determines how much memory can be physically installed, it is the chipset which determines how much memory can be physically addressed.

32-bit operating systems can *utilize* up to 4 gigabytes *IF* the memory is addressable.
64-bit operating systems can *utilize* up to 16 exabytes *IF* the memory is addressable.

~Adrian

#6
xieqiao

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You are right for Mac OS system and even Mac Tiger supports more than 4 GB memory. But for vista, it's a different story.

I have upgraded my OS to vista 64-bit, but it still shows 3.25 GB physical memory. Then I upgraded my 945PL mainboard to P43 Neo, and at last, it shows 4 GB physical memory.

http://www.appleinsi...pc_swindle.html

Note that this doesn't mean that MMIO "eats up" your RAM, it's just that the hardware maps that device-related memory over the top of physical memory, leaving fewer addresses available to the operating system to use for its system RAM. This problem is tied to 32-bit chipsets, which are independent from the CPU. There are 64-bit PCs with 32-bit chipsets.

That means that while they can execute 64-bit code and handle 64-bit virtual memory, they still can't address more than 4GB of physical RAM, minus roughly 0.75 GB of MMIO, for a grant total of 3.2GB usable RAM. If you install a full 4GB, the portion in conflict with the MMIO will simply not be used. For PC users installing a high end video card with 1GB of VRAM, the additional MMIO becomes an even greater problem: their usable system RAM shrinks by down to around 2.3GB.

#7
Adrian Fogge

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Um... I hope that you realize that by replacing your motherboard with a P43 Neo, you actually *changed* your chipset, thereby changing it's memory controller.

~Adrian





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