AIX for IBM system 370

On 2/1/16 8:11 PM, Eric Smith wrote: You have to remember that IBM called all of it's UNIX products AIX regardless of where they came from. IX/370 was prior to the AIX naming and if I recall, that was done by Interactive. AIX/370 and AIX PS/2 actually were the same code base (as opposed to AIX RT and AIX 3...RS/6000). Those code bases were from Locus Computer Corporation. The AIX in the quote was regarding AIX for the RS/6000. The kernel for AIX on the RS/6000 bore no real resemblance to any other Unix kernel. That was mainly due to the size of the virtual address space of the Power processors. At the time (32-bits) the Power CPU supported a 52-bit virtual address space and with 256MB segments, it was possible to map the 4GB address with 16 segment registers also because Power used "inverted page tables", there was no real notion of reloading the page tables. The page table described the full 52-bit address space. So to do an address space switch, you just needed to reload a significant set of the segment registers (actually quite fast). What the kernel did was to allocate each data structure as an array and pointed a segment register at it. Since at that point, virtual addresses were "free", it was just point a segment register at the array and away you go. Pretty much everything in the kernel was an index into an array. Which array, was determined by the segment register. Yes, it was alien (vs traditional Unix kernels) but it was simple and quite fast. TTFN - Guy