Re: Address bits again, Article on new mainframe use

Lawrence D'Oliveiro wrote:

On Mon, 2 Sep 2024 10:11:48 -0000 (UTC), John Levine wrote:

The IBM mainframe linkers had complicated ways to build
overlays and squeeze programs into 64K or whatever.

 So did DEC. They even introduced an additional version of their “Task
Builder” (“TKB”, the RSX-11 linker, which also ran on RSTS/E) that could
build larger programs than the regular one: it was called the “Slow Task
Builder” (“SLOTKB”).
 I never quite learned how to build overlaid programs. I tried to help a
friend with this once, by going over the documentation with him to try
clarify how to construct his .ODL (“Overlay Description Language”) file,
but I don’t think he got as far as doing an actual build before the
problem went away.

Turbo Pascal had overlay support for a while, I did try it once. Afair it used a base layer thunking system where all cross-module calls passed through these thunks which would check that the correct overlay was currently loaded, swapping it in if needed. This was OK for making a bunch of calls from the base to a single overlay, but trashed horribly if/when you had calls between two different overlays.
Terje
--
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"