[HECnet] DECnet Implementation and Productization of RSX-11M, 11S, 11D and IAS (was Re: Anonymous FAL (Tops-20))

On 2019-07-15 17:36, John Forecast wrote: Not only that. Device drivers were expected to manipulate event flags of other tasks directly, and then inform the OS that a significant even happened, which could force rescheduling of tasks. And it seems every driver had the code to do this work inline in the driver. So all kind of I/O completion becomes sortof messy. I think the driver is still expected to switch to kernel mode before doing this work, and also copy the IOSB data to the requesting task. Not sure exactly how a think like a swapped out process was handled in this case, but maybe the task was always locked in memory if I/O was active. Right. And I/O completion is normally handled by a couple of routines in the kernel, so the driver itself can be pretty minimal. Nah. 11M+ is really very similar to 11M. They pretty much share the same codebase, but M+ extends some data structures with a bit more information, and also adds a couple of more structures to make the system more flexible. The splitting of I/D space, as well as supervisor mode actually have very little impact on the kernel. There is obviously a bit more work at a context switch, and there are a couple of details around ASTs, which can switch between user and supervisor, but much of the rest don't know or care. And drivers can pretty much be moved straight over, although you normally would want to modify them to take advantage of some nifty additional capabilities provided by M+. No. Last/latest release was in 1998/1999 (depends on whether you look at 11M or 11M+). But it was still all just phase IV. Latest 11M is V4.8, and latest 11M+ is V4.6. I think they are even available to trailing-edge... Johnny -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt at softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol