>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 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. >We were still struggling with VSCR long after MVS/XA was GA. One problem was the inability of applications to exploit 31-bit, so VSCR continued far longer than it needed to. This isn't the case in z/OS. Despite the caveat of claiming that we'll never need that much storage, the reality is that 2GB is a phenomenally large amount of storage for executable code. So, other than consuming it in memory residency requirements, it is not something there is a pressing need to change. Adam ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
