Format of realmode interrupt return on stack

smeezekitty · 04-10-2010, 11:47 AM

What is the realmode interrupt return on the stack.
Is it pop AX pop CS or vice versa?

Sergei Steshenko · 04-11-2010, 04:50 AM

Quote:

Originally Posted by smeezekitty

What is the realmode interrupt return on the stack.
Is it pop AX pop CS or vice versa?

Isn't it the programmer who decides on the order of of pushes, and thus the order of pops ?

theNbomr · 04-11-2010, 10:49 AM

Uhh, 'POP CS' is effectively performed by the 'IRET' instruction. Only a very cleverly crafted program can work without crashing on execution of 'POP CS'. Are you trying to play tricks with self-modifying code, or some such other unconventional methods?
--- rod.

smeezekitty · 04-11-2010, 01:14 PM

I am implementing multitasking.
What i need to know is, is CS at the top of the stack or IP on the top of the stack when in an iret format?

theNbomr · 04-11-2010, 01:43 PM

Okay. From Rector & Alexy, "The 8086 Book": The INT instruction (same behavior as a hardware interrupt) pushes the Flags register, pushes CS, and then pushes IP. Therefore, IP would be at top of stack. Not sure how this relates to AX or multitasking, but there you have it.
--- rod.