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INSTRUCTION SET REFERENCE
PUSHA/PUSHADPush All General-Purpose Registers
Description
These instructions push the contents of the general-purpose registers onto the stack. The regis-
ters are stored on the stack in the following order: EAX, ECX, EDX, EBX, EBP, ESP (original
value), EBP, ESI, and EDI (if the current operand-size attribute is 32) and AX, CX, DX, BX, SP
(original value), BP, SI, and DI (if the operand-size attribute is 16). These instructions perform
the reverse operation of the POPA/POPAD instructions. The value pushed for the ESP or SP
register is its value before prior to pushing the first register (refer to the Operation section
below).
The PUSHA (push all) and PUSHAD (push all double) mnemonics reference the same opcode.
The PUSHA instruction is intended for use when the operand-size attribute is 16 and the
PUSHAD instruction for when the operand-size attribute is 32. Some assemblers may force the
operand size to 16 when PUSHA is used and to 32 when PUSHAD is used. Others may treat
these mnemonics as synonyms (PUSHA/PUSHAD) and use the current setting of the operand-
size attribute to determine the size of values to be pushed from the stack, regardless of the
mnemonic used.
In the real-address mode, if the ESP or SP register is 1, 3, or 5 when the PUSHA/PUSHAD
instruction is executed, the processor shuts down due to a lack of stack space. No exception is
generated to indicate this condition.
OpcodeInstruction
Description
60
PUSHA
Push AX, CX, DX, BX, original SP, BP, SI, and DI
60
PUSHAD
Push EAX, ECX, EDX, EBX, original ESP, EBP, ESI, and EDI
