Category : Pascal Source Code
Archive   : INFOS155.ZIP
Filename : PAGE_19.INF

This page displays programs that use the Alternate Multiplex Interrupt.

The Alternate Multiplex Interrupt is a standard created by Ralf Brown as
an alternative to the older Int 2Fh Multiplex. The AMI uses Int 2Dh
instead.

Programs chain into the interrupt looking for a 'signature' byte to be
passed in one or more CPU registers. If they are correct, a resident
program can act on it. If not, it's supposed to continue and call the
program that was previously in the chain. Unfortunately, no real standard
was set up, and with only 255 values possible, conflicts often happen.
Even worse, with more and more programs hooking into the interrupt,
execution speed could be seriously affected.

Ralf Brown (who oversees the Interrupt Listing, and is the author of
several PD/shareware programs) created this alternate format with strict
controls in mind. Programs are required to search for a free signature
byte, and some commands are standardized. Also, some data structures are
standardized to make detection and information gathering easier.

Some programs now use the Multiplex interrupt only for detection, and
return an address to call to actually do anything. The AMI also
standardizes this.

There aren't too many programs using the AMI yet. Most are currently
PD/Shareware programs.