[Simh] B5500 idle detection

[David Wijnants]

I have just started using the new Burroughs B5500 emulator with MCP XIII.
Thanks to Paul Kimpel's and Richard Cornwell's sites, the PDFs at
bitsavers.org, and considerable head scratching, I now have it running the
timesharing MCP, and CANDE listening on port 2000. It's wonderful to be
able to play with this classic architecture and an OS that was written
entirely in ALGOL nearly ten years before UNIX. Before Multics, even.

Anyway. The only problem is that my laptop's CPU fan is constantly
spinning at eleven. I have "set cpu idle" in my initialisation file, and
"show cpu" reports "idle enabled", but CPU usage is constantly at 100%.

Have I missed some undocumented "set" option?

David Wijnants.

[Richard Cornwell]

Hi Dave,

Post by David Wijnants
I have just started using the new Burroughs B5500 emulator with MCP
XIII. Thanks to Paul Kimpel's and Richard Cornwell's sites, the PDFs
at bitsavers.org, and considerable head scratching, I now have it
running the timesharing MCP, and CANDE listening on port 2000. It's
wonderful to be able to play with this classic architecture and an OS
that was written entirely in ALGOL nearly ten years before UNIX.
Before Multics, even.
Anyway. The only problem is that my laptop's CPU fan is constantly
spinning at eleven. I have "set cpu idle" in my initialisation file,
and "show cpu" reports "idle enabled", but CPU usage is constantly at
100%.
Have I missed some undocumented "set" option?

Idle detection should be working. Unless something has changed in SCP
since I released the simulator. Idle detection is based on detecting
the following tight loop that MCP uses when it has nothing to do.

ITI
TUS
OPDC ...
LOR
OPDC ...
NEQ
LITC 10 or LITC 1
BBC or LBC

Once it finds this loop it sees if the CPU executes a TUS at that
address.

I verified that it is detecting the IDLE loop, however it does not
seem to be entering idle state. Perhaps something changed in SCP.

Rich

[Richard Cornwell]

Hi David,

Post by David Wijnants
I have just started using the new Burroughs B5500 emulator with MCP
XIII. Thanks to Paul Kimpel's and Richard Cornwell's sites, the PDFs
at bitsavers.org, and considerable head scratching, I now have it
running the timesharing MCP, and CANDE listening on port 2000. It's
wonderful to be able to play with this classic architecture and an OS
that was written entirely in ALGOL nearly ten years before UNIX.
Before Multics, even.
Anyway. The only problem is that my laptop's CPU fan is constantly
spinning at eleven. I have "set cpu idle" in my initialisation file,
and "show cpu" reports "idle enabled", but CPU usage is constantly at
100%.
Have I missed some undocumented "set" option?

I have fixed this bug and it is now part of the main simh repo.

This was caused by my not calling the correct routines for the
inquiry console.

Rich