Bulletin number:  342
Products affected: D705B
Description: iconf problems
Component: iconf
Date: Fri Sep 7 11:25:43 BST 1990
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Some more work has been done on the iconf problems mentioned in
Bulletins 0054 and 0028 to produce what is thought to be a definitive
workaround. Anyone coming across exceptions to the following should
send the details with the smallest source possible to UK support who
will then consolidate and distribute the info.

Following the rules below when writing .pgm files should produce
bootable and debuggable .btl files. Deviation from these rules produces
unpredicatable results; sometimes unbootable .btl files, other times
files which boot but confuse the debugger. And even files which work
perfectly. So at least follow them in the first instance and then
modify if you need to once you have a working program:

1/	#USE all SCs called from configuration level before #USEing any
	SCs not called from configuration level (See Bulletin 0054).

2/	Put all #USE statements at the beggining of the .pgm file.

3/	When using constructs of the following form in .pgm files:

	PLACED PAR i=2 FOR num.of.procs
	  PROCESSOR i Txxx	<-- T8xx & T4xx
            func(a,b)
	
	PLACE an array of fifty bytes in WORKSPACE. Fifty bytes is the
	minimum necessary to avoid the error message:

	Booting root transputer...
	Error - iserver - unable to write byte xxxx to the boot link.

	when attempting to boot the .btl file in all the cases we have been
	able to test.

4/	When placing small processes on Transputers even if no replicated PAR
 	is used, also PLACE a fifty byte array in workspace as in 3 above.

With larger pieces of code per processor the array size can be  reduced
on a trial and error basis if memory is really tight. In  cases with a
large amount of code per processor  the array PLACEment becomes
unnecessary.
	
Below is an example .pgm file the layout of which works for everything
we have tried.
	
#INCLUDE "hostio.inc"
#INCLUDE "linkaddr.inc"

#USE "main.c4h"
#USE "func.c4h"
#USE "funclast.cah"

VAL num.of.procs IS 4:

CHAN OF SP fs,ts:
[num.of.procs]CHAN OF BYTE up:

PLACED PAR
  PROCESSOR 0 T800
    PLACE ts AT link0.out:
    PLACE fs AT link0.in:
    PLACE up[0] AT link2.in:
    main(fs,ts,up[0])

  PLACED PAR i = 1 FOR (num.of.procs - 2)
    PROCESSOR i T414
      PLACE up[i-1] AT link1.out:
      PLACE up[i] AT link2.in:
      [50]BYTE array:
      PLACE array IN WORKSPACE:
      func(up[i],up[i-1])

  PROCESSOR (num.of.procs - 1) T414
    PLACE up[num.of.procs - 2] AT link1.out:
    funclast(up[num.of.procs - 2])