On Sun, 2 Jun 2024 21:38:11 +0000, Seymour J Metz wrote: > ... >I've seen two different versions of the history posted here. One version >claimed that IBM intended on having paging from the beginning, but delayed it >due to engineering problems. The other version is that IBM decided after the >fact to add paging. I suspect that this is in the realm of if I knew they'd >have to shoot me. > The legend I heard was that Gene Amdahl deemed the performance cost of DAT, etc. unacceptable.
Storage consistency was long based on effective address which vould be determined before DAT generated a physical address and no IBM product wold map the same physical page to two different virtual addresses. UNIX shared memory violates that and required redesign of the consistency logic. The cost of false positives when two different address spaces mapped the same effective address to different physical addresses was deemed less than the cost of deferring the test to physical address. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
