Why is Maximum RAM Memory Limited to 4 GB with a 32-bit Address Bus?

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Discussion Overview

The discussion centers around the limitations of maximum RAM memory in relation to a 32-bit address bus, exploring the implications of addressable memory space and the potential for extensions through modern technology.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant states that a 32-bit address bus can address a maximum of 4 GB of RAM, equating this to 2^32 bytes.
  • Another participant notes that 64-bit systems can address significantly more memory, specifically 2^64 bytes.
  • A different participant introduces the concept of Physical Address Extension (PAE), explaining that it allows for extending the address bus from 32 bits to 36 bits, potentially increasing RAM capacity from 4 GB to 64 GB while maintaining compatibility with 32-bit applications.
  • One participant reiterates the relationship between bits and memory sectors, suggesting that each bit corresponds to a sector in physical memory.

Areas of Agreement / Disagreement

Participants generally agree on the basic calculations regarding memory limits imposed by a 32-bit address bus, but there are differing views on the implications of Physical Address Extension and its effectiveness in increasing RAM capacity.

Contextual Notes

The discussion does not resolve the effectiveness or limitations of Physical Address Extension, nor does it clarify the specific conditions under which it operates. There is also no consensus on the practical implications of these memory addressing schemes.

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Why, with a 32-bit address bus , we can only have a maximum of 4 GB RAM memory?
 
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4GB = 2^32 bytes.

64-bit can address 2^64 bytes.
 
Thank you!
 
but remember that most CPU's in todays market support Physical Address extension along with many Operating systems. All it does is extend the address bus from 32 bits to 36 bits but is still compatible with 32 bit applications and stuff. But if needed this can extend the amount of RAM from 4GB to 64GB. Thats quite the difference.
 
rty640 said:
4GB = 2^32 bytes.

64-bit can address 2^64 bytes.

Yeah, I believe that every bit represents a sector (usually a byte) in physical memory.
 

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