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In a Computer architecture book, I studied that Pentium IV has 64 bits bus width and addressable memory of 64 gigabytes. Does it mean that a computer running Pentium IV can support 64GB RAM, if supported by the OS?

Vibhav
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  • https://stackoverflow.com/questions/8869563/how-much-memory-can-be-accessed-by-a-32-bit-machine – 9dan Dec 25 '17 at 15:55
  • Money rules also in the chip manufacturing business. Packages and pins of chips cost money. So, while internally a CPU/North - South bridge design might be able to address the full range, ever so often, not all address lines are bonded to a pin of the chip. What point would it make to make available the full range at an extra cost if at that time, the majority of systems were hosting 1-4GB of RAM? Even today you will not often find CPU/motherboards which support the full theoretical range. – BitTickler Dec 25 '17 at 18:31

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This is so-called Physical Address Extension, which was supported by both Intel and AMD processors. Yes, with proper OS support 64Gb of RAM could be addressed. PLease read https://en.wikipedia.org/wiki/Physical_Address_Extension for more information

Severin Pappadeux
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