On Thu, 11 Feb 2016 13:36:10 +0530, Jake Anderson wrote: >Recently I saw an article about IPLING with 31 bit will no more exist after >z13 hardware. So what is the difference between IPLING with 31 bit and 64 >bit ? How is it going to make a difference ?
First, a pedantic terminology correction. It is not 31-bit vs. 64-bit. It is ESA/390 mode vs. z/Architecture mode. There are many differences between ESA/390 architecture and z/Architecture. These are described in some detail in the beginning of the z/Architecture Principles of Operation. For example, z/Architecture uses 64-bit addresses, so all of those places where an address is defined are 64 bits wide. PSW address is an obvious one. Also, the locations for the old and new PSW for SVC, I/O, External, Restart, Machine Check, and Program interruptions now require 16 bytes. Dynamic Address Translation tables (page and segment tables, etc.) require 64 bits for addresses. Likewise for Control registers. How is it going to make a difference? It likely simplifies the operating system somewhat. To an application program, it won't make any difference. Since release 1.5, z/OS can only run on z/Architecture hardware. Early in the IPL, it tells the hardware to switch into z/Architecture mode, and it stays that way. So all of your programs are already running in z/Architecture mode. They can use 24-bit, 31-bit or 64-bit addressing. -- Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
