On Tue, 11 Jun 2013 10:51:07 -0500, John McKown wrote: >Also, there is the SAM instruction to change AMODE as needed without >branching (well except for the horrible case where you are RMODE(31) and >switch to AMODE(24) causing a really nasty "branch" to occur).
Nope. That causes a specification exception. <quote from the POO> The instruction is completed only if the new addressing mode and the unupdated instruction address in the PSW are a valid combination. When the new addressing mode is to be the 24-bit mode, bits 64-103 of the unupdated PSW must be all zeros, or, when the new addressing mode is to be the 31-bit mode, bits 64-96 of the unupdated PSW must be all zeros; otherwise, a specification exception is recognized. </quote> -- Tom Marchant
