The document outlines the process of task switching using the 80486 processor's task state segment (TSS). Each task is assigned a TSS that includes register contents, task selector, and a link to the previously executing task. It details both direct and indirect methods of task switching, highlighting the steps involved in loading TSS and copying register values for the new task.

1. Task Switching
80486

2. Invisible Registers

3. Task State Segment ( TSS )
• Each task is assigned a Task State segment
• TSS contains-
 Registers and flag contents
 Selector for tasks LDT
 Link to TSS of prviously executing task ( Call / INT )

4. TSS

7. Task Switch
• Call / Jump
 Directly Point
 Indirectly Point via Task Gate
• INT
 Indirect via Task Gate
• IRET

8. Task Switch using TSS- direct
1. CALL / JMP - FAR
Segment --- Selector
2. CPL & RPL <= DP[L
if no --- exception
3. Check if TSS is in memory
if no loaded into memory by exception ISR
4. Copied Current Task's Register content to Current Tasks TSS
5. Load TR with selector & descriptor of new task TSS
6. Registeer values copied from TSS into registers
7.New task Begins.

10. Task Switch using TSS- indirect- Task Gate
1. CALL / JMP - FAR
Segment --- Selector
2. CPL & RPL <= DP[L
if no --- exception
3. Task Gate
Selector --- Descriptor
4. Check if TSS is in memory
if no loaded into memory by exception ISR
5. Copies Current Task's Register content to Current Tasks TSS
6. Load TR with selector & descriptor of new task TSS
7. Registeer values copied from TSS into registers
8.New task Begins.