On Tue, 30 Apr 2013 12:52:36 +0800, Timothy Sipples wrote: > >1. AMODE64. In certain languages on certain machines on certain releases of >z/OS a 2GB executable program code limit is enforced while there is no >corresponding restriction on data. That is, with such >languages/machines/releases code must reside below the bar while data can >reside anywhere within a 64-bit address space. (Note that IBM started >supporting above-the-bar code execution particularly in z/OS 1.13 and >particularly with Java, so the AMODE64 code/data distinction is getting >less relevant over time.) > My understanding is that this is entirely a software limitation of older releases of z/OS. As long as 64-bit addressing existed, if one could disable _all_ interrupts one could branch to code above 2GB; execute it, and branch back and re-enable. Linux, for example suffered no 31-bit limitation running on the same hardware.
I believe the current release of z/OS will even tolerate interupts from above the bar, but very few system services are available from there. I don't know how it keeps a 128-bit PSW. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
