PDP-11/34

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PDP-11/34
Manufacturer: Digital Equipment Corporation
Architecture: PDP-11


A PDP-11/34 partially disassembled; the board on the left is for the KY11-LB Programmer's Console

The PDP-11/34 was DEC's lower-cost replacement to the PDP-11/40 as the low-end PDP-11 system capable of running time-sharing, using memory management; it had the limited memory management capabilities of the PDP-11/40, though. It was a UNIBUS machine; as such, it was normally limited to 248KB of main memory.

The CPU came in two variants: the KD11-E (M7265 and M7266), and the plug-compatible replacement KD11-EA (M8265 and M8266).

The latter had provision for the FP11-A floating point unit, and the KK11-A cache (the system could use either, or both).

Both could be provided with either the KY11-LA Operator's Console (a limited functionality console with only halt and boot functionality), or the KY11-LB Programmer's Console.

Apparently it was cloned in the Soviet Union as the SM 1420.

Register access

Like its predecessor PDP-11/05, the general registers (R0-R5, SP and PC) have addresses assigned to them; they are also accessible from the UNIBUS, and therefore from the KY11-LB Programmer's Console, when the machine is halted. Their addresses are:

Address Register
777700 R0
...
777705 R5
777706 SP
777707 PC

Note that the registers are word-accessible at odd addresses on the UNIBUS (unlike any other device); and their addresses, like those on the -11/05, increment by 1, not by 2, as is usual for word-sized items.

In addition, some internal CPU registers are available at addresses 777710 -777717.