PDP-15
| PDP-15 | |
| Manufacturer: | Digital Equipment Corporation |
|---|---|
| Year First Shipped: | February, 1970 |
| Form Factor: | minicomputer |
| Word Size: | 18 bits |
| Logic Type: | TTL ICs |
| Clock Speed: | 1.6 μsec (basic instructions) |
| Memory Speed: | 0.8 μsec |
| Physical Address Size: | 17 bits (128K words) |
| Virtual Address Size: | 12 bits (direct), 15 bits (indirect), 17 bits (indexed) |
| Memory Management: | bounds register; base and bounds pair (both optional) |
| Operating System: | DECsys, Keyboard Monitor System, Foreground/Background System, DOS-15, XVM/DOS, XVM/RSX, XVM/MUMPS, Advanced Monitor System |
| Predecessor(s): | PDP-9 |
| Successor(s): | None |
The PDP-15 was DEC's last 18-bit computer, and the only one implemented using integrated circuits. Its principal intended use was for real-time systems. A variety of models were offered, from the PDP-15/10 (with 4K words of main memory, to the PDP-15/40 (with 24K words, and two disks).
Instructions had a 4-bit opcode, one bit of indirect, and one of indexing. It was a load-store architecture, with a single accumulator. There were several other specialized registers, including an 'Index Register', and a 'Limit Register' for loop control.
Both multiply and floating point support were hardware options (the former being standard on all but the lowest model). The floating point unit, the FP15, was a complete separate processor, but shared the instruction set space with the basic CPU.
KM15 memory management included a boundary register to set the boundary between protected and un-protected memory, and two modes for the CPU. A memory relocation option, the KT15, with a base and bounds register pair, was also available.
Further Reading
- "PDP-15 Systems Reference Manual"
