On Wed, 1 Dec 2010 12:13:46 -0800, Gerhard Adam wrote: >>Huh? We're discussing how to get around that restriction. > >The point is that there is nothing to "get around". Executable code isn't >supported about 2GB for numerous reasons already mentioned. Therefore the >middle 64-bits of the z/architecture PSW only contain zeros. Compressing >the PSW doesn't incur the loss of any data. Data loss would occur only if a >64-bit instruction address had to be preserved, but since that isn't valid, >there is nothing lost. > >If you attempted it, then you would experience instruction address >truncation of the high order bits. > >Once again, there's nothing to "get around", since it simply isn't allowed.
The discussion has been about what IBM would have to do to allow code to run above the bar. One of the big issues is that PSWs are stored in control blocks in 64-bit form. Ed was suggesting a method that IBM could use to get around the problem of some programs that alter the PSW in, for example, an RB. Perhaps you believe that IBM will *never* support code above the line. I don't happen to think that they are that short-sighted. We have already seen that thee loader can load data-only CSECTs above the bar. I suspect that there is more to come. -- Tom Marchant ---------------------------------------------------------------------- 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
