 As the chain of ISRs is singly linked, there is no provision for discovering the previous handler's address (other than attempting to trace back the interrupt chain), or to inform its predecessor that it needs to update its "next address to which to jump" not to point to the TSR which desires to remove itself, so that in order to safely unload TSRs in the middle of a chain, stubs have to be left in memory in most cases, thereby causing memory fragmentation.This gave rise to TSR cooperation frameworks such as TesSeRact and AMIS.To manage problems with many TSR programs sharing the same interrupt, a method called "Alternate Multiplex Interrupt Specification" (AMIS) was proposed by Ralf D. Brown as an improvement over previously used services offered via INT 2Fh.