starnakin/42_KFS
1
2
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

add: documentation: memory

Browse Source
This commit is contained in:
Starnakin
2024-10-30 19:05:58 +01:00
parent 5fba376e2f
commit 04211e2773
9 changed files with 134 additions and 65 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
documentation/memory/mmu.md Normal file
View File

@ -0,0 +1,19 @@
# Memory Management Unit (MMU)
The MMU is a chip which translate virtual memory to physical memory. When you try to access to an address (/!\ only when you try to access) the MMU will get the physical address from the [pd](./page_directory.md).
## How translate an address ?
The address will be divid in 3 parts:
- Page Directory index (10bit (cause 1024))
- Page Table index (10bit (cause 1024 too))
- offset (12bit cause page size = 4096)
### Example
**address**: 0b000100000011101011111011101101
| Base | PD index | PT index | offset |
|--------|----------|------------|--------------|
| Binary | 00010000 | 0011101011 | 111011101101 |
| Decimal| 16 | 235 | 3821 |
So to translate this address the MMU will get the 20 first bit of the value store at the 235th PTE of the 16th PDE and will replace the 20 first bit of the virtually address.