Hardware architecture: Peripheral Processors

6000 series memory block (4096 words,12bits) A Peripheral Processor or PP was logically a processor on its own with its own PP instruction set and programs. The main task of PP programs was input and output and housekeeping.

Each PP had 4096 words of 12 bits memory (see photo). This PP memory was equivalent to one (1) core memory block. Later 800-series systems had 8K words of 16 bit SECDED memory. The limited instruction set allowed internal processing, read/write to Central Memory, read/write to I/O channels and exchanging the CPU.
There was only one accumulator and there were direct cells (like in the PDP8) that allowed efficient and compact 12 bit instructions.

PP barrel concept

PP's were organized in groups of ten (in the 800-series systems in groups of 5) or barrels. As said before, each PP was perceived as a single, separate processor in the system. In reality, only one hardware processor serviced a complete barrel of PP's. Using shift-registers, PP instructions were processed in either one, two or 5 minor (memory read/write) cycles. For the CYBER 840 system that meant that each PP register moved through the barrel at a 20 MHz rate, causing each PP tio run at four MHz.
Each PP barrel had a:

At a deadstart, all PP's were forced to do a loop for input available on their "own" channel. As the first bytes from the deadstart panel were forced into PP0, PP0 (MTR) was responsible to output the Standard Library (STL) to each PP on its own channel during the start-up phase of the system. Deadstarts could be initiated by using a hardware button between the two console "eyes" or under the single console screen in later systems. Another way was using the deadstart switch adjacent to the deadstart panel. After some time, system programmers and operators were very experienced in "toggling in" the deadstart program in the 16 or 20 rows with switches. It was always amazing that one could (warm)start from a deadstart tape (later a disk) using only seven to 12 PP words located in the deadstart panel.

       01 1402        LDN  2         load 2

       02 73ch        OAM  out,ch    output 2 words from 17B on ch

       03 0017

       04 754ch       DCN  ch        disconnect channel ch

       05 77ch        FNC  120B,ch   function 120B on ch

       06 0120

       07 74ch        ACN  ch        activate ch

       10 71ch        IAM  7301B,ch  read (A) words from ch to 7301

       11 7301

       12 0710        MJN  hang

       17 0000   out  0000

       20 7112        7112

       21 0000   hang

Sample deadstart panel program


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