This has never been clear for me. Modern CPUs have the addressable space of 64 bits. The most expensive part of adding more memory is obviously the memory hardware itself, chips on them, etc. But why do motherboards also always impose the limitation? Is there a downside in supporting all 64 bits to pass the signal between CPU/controller/physical memory?
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Also: Why do 64 bit systems have only a 48 bit address space?– Mokubai ♦Aug 20, 2016 at 20:39
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Motherboards have the limit the chipset they implement have. The chipset is designed by AMD and Intel.– RamhoundAug 20, 2016 at 21:04
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48-bit is ~280TB. 8GB is only 33 bits. So in the case of 8GB the address space is only expanded by 1 bit over the 32-bit space. Does every bit supported by the chipset really come at such a great expense that this has to translate to the limit on the physical memory?– Grammar AddictAug 20, 2016 at 22:56
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