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
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