On Wed, 1 Dec 2010 06:53:55 -0800, Gerhard Adam wrote: >>The same thing happened with 370 to XA, and probably with revolutions in >previous versions (I wasn't there for them). > >Actually it wasn't the same, since the size of the registers/PSW didn't >change during that entire period. Therefore, while their usage changed, >there were no
Were there 7 uncommitted bits in the PSW to save the corresponding bits in the instruction address, or was additional information moved to Control Registers which then needed to be stored? >Issues related to storing such values. Changing the displacements and >layout of control blocks is a major departure and seems virtually impossible >to maintain any kind of downward compatibility once such a change is made. > Much (most?) of that work must already have been done. 64-bit registers must be saved and restored across interrupts, else 64-bit operations would be impossible for problem programs. Is the only unfinished work the PSW? Is the PSW present in far more control blocks than the registers? -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
