OK, but I could argument that a specification exception definitely causes a nasty "branch" to occur. <grin/>
On Tue, Jun 11, 2013 at 1:39 PM, Tom Marchant <[email protected]>wrote: > 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 > -- This is a test of the Emergency Broadcast System. If this had been an actual emergency, do you really think we'd stick around to tell you? Maranatha! <>< John McKown
