12 Nov
2021
12 Nov
'21
7:17 p.m.
On 2021-11-12 19:06, Paul Koning wrote:
Yes. That was what I was thinking of/referring to.
On Nov 12, 2021, at 10:57 AM, Johnny Billquist
<bqt at softjar.se> wrote:
On 2021-11-12 15:24, Paul Koning wrote:
Same with -11M. But it's only used for the kernel.
However, in TOPS-20 as well as some other DEC OSes, this is a common pattern for all
programs.
In the sense that an executable program is basically a memory image? Yes, RT-11 SAV
files are a good example. On Nov
11, 2021, at 6:22 PM, Johnny Billquist <bqt at softjar.se> wrote:
I must admit that I hadn't considered the possibility of just saving the core. Which
of course can accomplish the same thing in a neat way.
That's a bit like how
RSX-11/D and IAS boot -- by reloading the image of memory when you issued the SAV command.
Pretty clever: you set things up the way you want them to be, and then you make that
state persistent. But the RSX-11/D and IAS case is a whole-system image,
not kernel or a single program. You boot the OS, load all the applications you want to be
active in their various partitions, and type SAV. When the system boots, that whole
memory image is loaded, and made active by delivering power-fail ASTs to each task. For
example, SAV also handles the boot-time setup, for example prompting for the current date
and time. (Or perhaps it doesn't do that in the stock version; I remember adding it
to SAV in 1978, as part of Typeset-11 work.)
Sorry, my comment about -11M was sloppy. It's the exact same story as
with IAS and -11D.
And no, it don't set things like date. I guess it could be done, but in
general it's not. SAV is responsible for saving all of memory into the
system image. At boot, SAV is resuming more or less where it stopped
during the saving. At that point it sets up a few basic things to
reflect which disk it booted from, and then kicks of
LB:[1,2]STARTUP.CMD, which can then do whatever else you want to do at
boot. And in there is where you normally find the setting of date/time.
In addition to SAV, there is also VMR, which is sortof like your normal
command line interpreter, but the commands does not affect the running
system, but instead manipulates the saved system image.
This way you can replace tasks, change all kind of stuff, change device
drivers and so on, on your system image without any other effects you
might have if you were to boot the system up, change, and run SAV.
And when you involve DECnet, there is also VNP, which again manipulates
the saved system image, but with all kind of things related to DECnet.
It is nice, in that it means you can in the end boot very fast up to a
running system, since most things can be pre-done in the saved system image.
And for something like RSX-11S, this is essential, since it is a memory
only system, with no local storage. (It can however run things loaded
via DECnet.)
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