[Simh] KL8-JA

[Bob Supnik]

Yeah, sorry.  It is a single line. The simulator treats all of them as a 
single device.

The limit of 4 lines comes from the (current) limit of 8 device 
addresses per device (in pdp8_defs.h). Further, the simulator assumes 
that the device addresses within a device are contiguous, and the 
additional serial lines use contiguous device addresses. It maps device 
# to line # as follows:

line # = (device # - base) / 2

This algorithm dates back to the PDP8/I and is documented in the 1970 
Small Computer Handbook.

According to the TSS documentation, up to 32 lines were supported. 
Clearly, they could not all be PT08s/KL8s, because that would use up 
every IO device number in the PDP8. According to the TSS/8 source I 
have, provision was made for 16 PT08/KL8s, with device number 
assignments as follows:

IFZERO DC08A <
     KSKIP+400        /K01    /KEYBOARD SKIP IOTS FOR PT08 AND KL8E
     KSKIP+420        /K02
     KSKIP+440        /K03
     KSKIP+460    >    /K04
     KSKIP+340        /K05; K01 IF DC08A WITH PT08'S
     KSKIP+110        /K06; K02 IF DC08A WITH PT08'S
IFNZRO CPU-1 <
     KSKIP+300    >    /K07; K03 IF DC08A WITH PT08'S
     KSKIP+320        /K10; K04 IF DC08A WITH PT08'S
     KSKIP+500        /K11; K05 IF DC08A WITH PT08'S
     KSKIP+520        /K12; K06 IF DC08A WITH PT08'S
     KSKIP+540        /K13; K07 IF DC08A WITH PT08'S
     KSKIP+560        /K14; K10 IF DC08A WITH PT08'S
     KSKIP+700        /K15
     KSKIP+360        /K16
     KSKIP+720        /K17
     KSKIP+060        /K20
     KSKIP+140        /K21
     KSKIP+160        /K22
     KSKIP+050        /K23

IFZERO DC08A <
     TSKIP+410        /K01    /TELEPRINTER SKIP IOTS FOR PT08 AND KL8E
     TSKIP+430        /K02
     TSKIP+450        /K03
     TSKIP+470    >    /K04
     TSKIP+350        /K05; K01 IF DC08A WITH PT08'S
     TSKIP+120        /K06; K02 IF DC08A WITH PT08'S
IFNZRO CPU-1 <
     TSKIP+310    >    /K07; K03 IF DC08A WITH PT08'S
     TSKIP+330        /K10; K04 IF DC08A WITH PT08'S
     TSKIP+510        /K11; K05 IF DC08A WITH PT08'S
     TSKIP+530        /K12; K06 IF DC08A WITH PT08'S
     TSKIP+550        /K13; K07 IF DC08A WITH PT08'S
     TSKIP+570        /K14; K10 IF DC08A WITH PT08'S
     TSKIP+710        /K15
     TSKIP+370        /K16
     TSKIP+730        /K17
     TSKIP+070        /K20
     TSKIP+150        /K21
     TSKIP+170        /K22
     TSKIP+650        /K23

The device number conflicts in this table are at least the following:

cassette/magtape (70)
TSC timesharing option (36)
floating point processor (55)

None of these are supported in TSS/8.

Bottom line: with some very significant surgery on the PDP8 simulator's 
core structures (DIB definition and IO device allocation) and a much 
more flexible device # -> line # algorithm in the KL8 simulator, it 
would be possible to extend the PDP8 to 16 additional lines. I don't see 
the point, but that's just my view.

/Bob