KT24 UNIBUS map option

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KT24 board

The KT24 UNIBUS map option is an option for the PDP-11/24 which provided a full path between its UNIBUS and Extended UNIBUS (EUB) via a UNIBUS map. It also provided a number of other facilities, including chip sockets for a bootstrap PROM set (compatible with those of the M9312), and a power supply voltage monitor for the system. The KT24 was implemented as a single hex printed circuit board, the M7134.

UNIBUS map details

The KT24 had standard UNIBUS map functionality; a set of 31 mapping register pairs in the KT24 mapped 8 Kbyte blocks of UNIBUS address space to any location within the 4 Mbyte main memory address space. A pair of jumper sets could limit the range of UNIBUS address space which was mapped; a control bit in the KT24's Last Mapped Address register causes the jumpers to be ignored, for diagnostic purposes.

If no KT24 was present, the CPU detected its absence, and turned on a set of drivers on the CPU card which gated the address from the UNIBUS through to the EUB. (Pin FE1 of the CPU slot, "UB to MA VIA UBMAP", is connected to a pull-up on the CPU board, and also runs to the slot where the KT24 is plugged in, where it is grounded if a KT24 is plugged in; that signal is used to generate "UB to MA", which is the cross-connection enable signal.)