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80386 Programmer's Reference Manual -- Opcode PUSHA

PUSHA/PUSHAD -- Push all General Registers

Opcode	Instruction	Clocks	Description	Example
60	pusha	18	Push AX, CX, DX, BX, original SP, BP, SI, and DI	`pusha`
60	pushal	18	Push EAX, ECX, EDX, EBX, original ESP, EBP, ESI, and EDI	`pushal`

Operation




IF OperandSize = 16 (* PUSHA instruction *)
THEN
   Temp := (SP);
   Push(AX);
   Push(CX);
   Push(DX);
   Push(BX);
   Push(Temp);
   Push(BP);
   Push(SI);
   Push(DI);
ELSE (* OperandSize = 32, PUSHAD instruction *)
   Temp := (ESP);
   Push(EAX);
   Push(ECX);
   Push(EDX);
   Push(EBX);
   Push(Temp);
   Push(EBP);
   Push(ESI);
   Push(EDI);
FI;

Description

PUSHA and PUSHAD save the 16-bit or 32-bit general registers, respectively, on the 80386 stack. PUSHA decrements the stack pointer (SP) by 16 to hold the eight word values. PUSHAD decrements the stack pointer (ESP) by 32 to hold the eight doubleword values. Because the registers are pushed onto the stack in the order in which they were given, they appear in the 16 or 32 new stack bytes in reverse order. The last register pushed is DI or EDI.

Flags Affected

None

Protected Mode Exceptions

#SS(0) if the starting or ending stack address is outside the stack segment limit; #PF(fault-code) for a page fault

Real Address Mode Exceptions

Before executing PUSHA or PUSHAD, the 80386 shuts down if SP or ESP equals 1, 3, or 5; if SP or ESP equals 7, 9, 11, 13, or 15, exception 13 occurs

Virtual 8086 Mode Exceptions

Same exceptions as in real-address mode; #PF(fault-code) for a page fault

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