The KD11-Z CPU was the CPU of the PDP-11/44; the letter code 'Z' was a tip to the fact that it was the last native UNIBUS PDP-11 CPU, and the last to be made out of discrete chips, and not a microprocessor.
The KD11-Z used the Extended UNIBUS for its bus to main memory, allowing it to have up to 4 mega-bytes of main memory. All devices were attached to a semi-separate UNIBUS (it and the EUB shared data lines, but not address lines); DMA devices could gain access to the memory via a UNIBUS map which connected the two, and mapped UNIBUS addresses to main memory addresses.
Full PDP-11 Memory Management and a cache (the KK11-B) were standard on all KD11-Z's. It also supported the optional FP11-F floating point (full FP11 floating point) and/or the KE44-A Commercial Instruction Set Processor; these plugged into dedicated slots in the CPU backplane (it could work with either, or both).
The basic KD11-Z CPU consisted of five hex boards:
- M7094 Data Path module
- M7095 Control module
- M7096 Multifunction module
- M7097 KK11-B Cache module
- M7098 UNIBUS interface module
These were placed in a 14-slot CPU-specific backplane, along with the optional FP11-F and KE44-A, and all the main memory cards (the EUB was only present on the main backplane), leaving two slots (one MUD/SPC slot, and one SPC slot, which also contained the 'UNIBUS out').
Board locations are:
|1||M7090 CIM||M7091 CIS|
|3||M7093 Floating point|
|4||M7094 Data paths|
|8||M7098 UNIBUS interface|
|10||M8722 MS11-M (optional)|
|11||M8722 MS11-M (optional)|
|12||M8722 MS11-M (optional)|
The standard mounting box for the CPU was the BA11-A, which is unusual in that it does not use only the standard DEC power distribution connectors; it also provided special connections on bus bars in its power supply, and the KD11-Z backplane uses unique Flexprint cables for power, which go to the special connections (see image).
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