Segmentation memory

anon19287473 · Post by **anon19287473** » Fri Mar 30, 2007 1:48 pm

How much memory can you access with segmentation (32-bit) and

how much w/ paging?

From only this perseptive (ignoring other pro's and con's), would segmentation be a good choice for a small OS I'm writing (mostly for practice, to "learn the ropes")?

Can you have memory protection with paging?

How can I detect the amount of RAM on a system, and adjust the GDT (if I need too)?

muisei · Post by **muisei** » Fri Mar 30, 2007 2:03 pm

With segmentation in protected mode you canaccess max 4GB.
With paging you can access max 64GB
The page can give you very robust protection mechanismPage and segment protection can be combined.

Read the "Intel Architecture Software Developer's Manual Volume 3:System Programming".Chapters 3 and 4 will answer your questions completely.

anon19287473 · Post by **anon19287473** » Fri Mar 30, 2007 2:04 pm

I read 4GB per segment, is that wrong?

frank · Post by **frank** » Fri Mar 30, 2007 4:00 pm

I read 4GB per segment, is that wrong?

No an X86 processor can only access up to 4GB at a time though one segment descriptor.