10 Apr
2026
10 Apr
'26
4:13 p.m.
Dave,
Johnny reminded me about a limitation of this FPEM, specifically it does not work with
tasks that have external headers. When you TKB your F77 program add the /-XH switch to
make a task that does not have an external header. RSX11M+ by default would have /XH on by
default.
As I recall (maybe wrongly), you don’t have to specify F77EIS when building the task,
as long as FPEM is running. Also, if you need FPEM to remove itself, I think you can
UNStop it and it will change the vectors back. I am interested in whether this will work
on RSX11M+ V4.6
Good Luck,
Mark
On Apr 10, 2026, at 7:47 AM, Dave McGuire
<mcguire(a)neurotica.com> wrote:
On 4/9/26 11:34, Mark Matlock wrote:
Since Fortran 77 is not much fun without
floating point, you may want to try the RSX Floating Point Emulator.
Glenn Everhart released this floating point emulator on the Fall 82 RSX SIG tape in
[312,315]. In 1984, my lab acquired a PDP-11/44 but it did not have a FPP. We used this
FPEM software to be able to use Fortran 77 floating point operations. At that time we were
running RSX11M+ V2.1 or maybe V3.0 It continued to be used until at least 1993 or so.
It works by putting a vector to its code which it partially locates in pool to trap
illegal instructions. If the instruction was a FP instruction then it does the work in
software and returns to the user code. It should be FIXed in memory, if it is checkpoint
or moved by a shuffle to a different location after it runs, it will crash RSX. I’d fix it
in memory early in STARTUP.CMD.
I did verify that the FPEM.MAC compiles & links clean on RSX11M+ V4.6, but I
didn’t have an easy way to test it. Below is a bit more info on it that is also in
FPEM.DOC
Thanks Mark! That would seem to be the perfect solution, lacking a functional FP11-C
board set. I was able to build and install it, but I wasn't able to get it to
actually work, so there may be a 4.6 compatibility issue. I'll be over there tomorrow
(or today if I can get there) to try again and take better notes. And then
it's...sysgen time!
I was able to get a non-FP program (just a "hello world") to run using F77EIS,
though, so that was a start.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
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