6-30 Vol. 3A

INTERRUPT AND EXCEPTION HANDLING

Interrupt 9—Coprocessor Segment Overrun

Exception Class

Abort. (Intel reserved; do not use. Recent IA-32 processors do not generate this 

exception.)

Description

Indicates that an Intel386 CPU-based systems with an Intel 387 math coprocessor detected a page or segment 
violation while transferring the middle portion of an Intel 387 math coprocessor operand. The P6 family, Pentium, 
and Intel486 processors do not generate this exception; instead, this condition is detected with a general protec-
tion exception (#GP), interrupt 13.

Exception Error Code

None.

Saved Instruction Pointer

The saved contents of CS and EIP registers point to the instruction that generated the exception.

Program State Change

A program-state following

 a coprocessor segment-overrun ex

ception is undefined. The program or task cannot 

be resumed or restarted. The only available action of the exception handler is to save the instruction pointer and 
reinitialize the x87 FPU using the FNINIT instruction.