
			NOTES on Geotronics Corp. UNIX

1) LIGHT REGISTER.  Setting `.lights' in "m40.s" before assembly causes
the *switches=>lights feature to be included.  This code samples the
memory word addressed by switches 15..1 each clock tick and displays
the contents of the addressed word in the lights.  If switch 0 is ON,
User space is used; otherwise Kernel space is used.  If a non-existent
address is supplied, all lights are turned on and sampling is delayed
for 2 seconds (to avoid repeated bus error traps).  WARNING: sampling
a device register (e.g., 177562) may cause unexpected side-effects.
DO NOT set `.lights' if there are not both switch and display registers.
(Note that PDP-11/34s and PDP-11/40s have no display register; some
PDP-11/34s don't even have a switch register, although this is not
supposed to be a supported configuration for a machine with over 28Kw
of memory.  G.C. supplies a switches & lights option for LSI-11/23s.)

2) MTPS/MFPS SUPPORT.  Setting `.cpu34' or `.cpu23' in "m40.s" before
assembly uses the MTPS & MFPS instructions to speed up processor
priority changes.  `.cpu34' also changes the segmentation-fault
instruction restart code for address mode 2.

3) FP11 SUPPORT.  Setting `.fp11' in "m40.s" before assembly includes
support for the FP11 floating-point processor (all flavors).  DO NOT
set `.fp11' if there is no FP11.

3) TERMINAL HANDLER.  Ctrl/S and Ctrl/Q are currently reserved for use
in terminal transmission synchronization (required for Diablo, VT100,
etc.).  These characters cannot be read from the keyboard even in "raw"
mode.

4) CLOCK REGISTER.  If a clock register is present, it is used; the LSI
"BEVENTL" clock will also work.  The "idle" routine re-enables
interrupts on the clock register (if present) and on the console
interface, to guard against loss of "interrupt enable" (which happens
fairly frequently with DL11-Ws, rumored to be due to static discharge).

5) BOOTSTRAP.  Ctrl/H (backspace) and Ctrl/U work properly during entry
of the boot file pathname.  The booted program can RTS PC to re-enter
the bootstrap, if it hasn't been overwritten.

6) RANDOM INTERRUPTS.  Interrupts with unexpected vector addresses
vector to "trap", which prints a message then resumes.

7) SYSGEN.  The "mkconf" utility has been upgraded to support these new
devices:
	dup     DUP11-DA        synchronous communications interface
	dz      DZ11            asynchronous terminal multiplexer
	dr      DR11-C          control interface for A/D system
	ad      DR11-C          A/D system interface (MTDR2)
	mp      MTX-512         Matrox bit-map display interface
	cr      CR11            card reader controller
	xy      XY11            pen plotter controller
	cs      CSS-1           Winchester disk and cartridge tape unit
	ct      TC-640          WPC controller for cartridge tape unit
The following devices are now UNSUPPORTED:
	pc      dc      dj      dp      hs

8) The "empty" system call has been added (sys 63.), as well as "access"
and "tell".

9) Other kernel changes have been made for various reasons; these are
transparent to applications programs and device drivers.
