Dobin 0x10_IntelArchitecture.pdf
Dobin 0x10_IntelArchitecture.pdf
Dobin 0x10_IntelArchitecture.pdf
Fichier Détails
| Cartes-fiches | 11 |
|---|---|
| Langue | English |
| Catégorie | Informatique |
| Niveau | Université |
| Crée / Actualisé | 21.06.2019 / 27.06.2020 |
| Lien de web |
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What are registers?
Registers are the "variables" on the CPU
Immnediate acces for the CPU
Cannot write Memory -> Memory
- Aways: Memory -> Register -> Memory
What can be held in registers?
Register can hold:
- Data (numbers)
- Addresses (also numbers, but with a different meaning)
What can registers be used for?
Registers can be used to:
- Perform computations
- Read / Write memory
- Execute instructions
Name some registers in a 32 bit system and their function.
- EAX -> Adding stuff
- EBX -> Referencing stuff
- ECX -> Counting stuff
- EDX -> Data stuff
- ESI -> Points to a source
- EDI -> Points to a destination
Name the 3 registars that contain instruction pointer, stack pointer and base Pointer. (32 bit)
- EIP -> Instruction Pointer -> Next instruction to be executed
- ESP -> Stack Pointer -> Top of Stack
- EBP -> Base Pointer -> Current Stack Frame (Bottom)
How does a CPU interpret instructions?
A CPU looks at bytes, and then decides what to execute based on them.
What is the difference between big and little endian?
Big endian: The most significant byte of the data is placed at the byte with the lowest address.
Little endian: The least significant byte of the data is placed at the byte with the lowest address.
What are the 2 most important rings in the ring modle and what are their characteristics?
Ring 0: Kernel (Kernelspace)
- Can be intercated with by using "syscalls"
Ring 3: Userspace
- Where all programs run
How to transit from userspace to kernelspace?
- System Calls (syscall)
Why can 32 bit processes only utilize 4GB of memory?
- 32 bit register size in Intel CPU
- Registers are used to address memory
- 2^32 = 4 billion = 4 gigabyte
There is only one CPU, how can:
- Mutliple programs run at the same time?
- The OS and the programs run at the same time?
Solution: Interrupts
- Timer interrupts
- In terrupts are handled by the kernel
- Time / clock
- Network interface
- USB devices
- Kernel schedules the different processes
What are the pros and cons of 64 bit systems?
64 bit pros:
- Can address more than 4 gb of memory per computer
- up to 4 Petabytes of ram
- 64 bit calculations are maybe a bit faster
64 bit cons:
- Programs use more space
- Because pointers and data-types (integer) are twice as big
- On disk, memory and most importantly: cache
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