> a 32-bit OS can only address 3.2 GB of RAM
I am wondering how these numbers stick together. I especially wonder why those extra 0.8 GB are unaccessible, when did that happen and who's the thief
I am wondering how these numbers stick together. I especially wonder why those extra 0.8 GB are unaccessible, when did that happen and who's the thief
3.2GB is an example figure - it could be 3.5GB, 3.6GB... - but reflects that RAM can't be mapped at all of lower 4GB. Memory controllers typically remap part of it to a range upper than 4GB boundary, so 32-bit PAE-capable or 64-bit OS can still use it.
OTOH using 64-bit OS is recommended with RAM >=1.5GB because if OS can't map all RAM _twice_ and all device memory to virtual address space, tricks with memory banking (frequent page remapping) are getting needed to deal with data move.
In researching this I learned that some 32bit hardware could utilize 128GB of ram using Physical Address Extensions. Each process is still limited to 4GB though.