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Revision as of 22:14, October 12, 2007
The PDP-11 series of computers from Digital Equipment Corporation were popular 16-bit mini-computers from 1970 through the early 1980s. The first model was the PDP-11/20, released in 1970. The successor to the PDP-11 line was the VAX series.
DEC sold its PDP-11 hardware and software rights to Mentec in 1994.
Architecture
Data size = 16 bits
Address size = 24 bits
16-bit Registers: R0, R1, R2, R3, R4, R5, R6 (SP), R7 (PC), PSW
The 11/70 had two sets of registers R0-R5.
The instruction set varied somewhat between the different models. There was a basic instruction set possessed by all models. In addition, some models supported additional instructions, and/or floating-point (32-bit and 64-bit), and/or other extensions. The EIS (Extended Instruction Set) supported Kernel, Supervisor, and User modes as well as additional numeric support. The CIS (Commercial Instruction Set) included 10 different forms of string manipulation instructions. The PDP-11/70 with a Floating Point Processor and CIS supported all of the possible PDP-11 instructions.
All I/O was through memory-mapped devices as the CPUs did not support I/O instructions.
PDP 11/70 instruction set: ADC, ADCB, ADD, ASH, ASHC, ASL, ASLB, ASR, ASRB, BCC, BCS, BIC, BICB, BIS, BISB, BIT, BITB, BEQ, BGE, BGT, BHI, BHIS, BLE, BLO, BLOS, BLT, BMI, BNE, BPL, BPT, BR, BVC, BVS, CCC, CLC, CLN, CLR, CLRB, CLV, CLZ, CMP, CMPB, COM, COMB, DEC, DECB, DIV, EMT, HALT, INC, INCB, IOT, JMP, JSR, MARK, MFPD, MFPI, MOV, MOVB, MTPD, MTPI, MUL, NEG, NEGB, RESET, ROL, ROLB, ROR, RORB, RTI, RTS, RTT, SBC, SBCB, SCC, SEC, SEN, SEV, SEZ, SOB, SPL, SUB, SWAB, SXT, TST, TRAP, TSTB, WAIT, XOR.
Commercial Instruction Set: ADDN, ADDNI, ADDP, ADDPI, ASHN, ASHNI, ASHP, ASHPI, CMPC, CMPCI, CMPN, CMPNI, CMPP, CMPPI, CVTLN, CVTLNI, CVTLP, CVTLPI, CVTNL, CVTNLI, CVTNP, CVTNPI, CVTPL, CVTPLI, CVTPN, CVTPNI, DIVP, DIVPI, L2DR, L3DR, LOCC, LOCCI, MATC, MATCI, MOVC, MOVCI, MOVRC. MOVRCI, MOVTC. MOVTCI, MULP, MULPI, SCANC, SCANCI, SKPC, SKPCI, SPANC, SPANCI, SUBN, SUBNI, SUBP, SUBPI.
Floating Point Processor instruction set: ABSD, ABSF, ADDD, ADDF, CFCC, CLRD, CLRF, CMPD, CMPF, DIVD, DIVF, LCDF, LDCFD, LDCID, LDCIF, LDCLD, LDCLF, LDD, LDEXP, LDF, LDFPS, MODD, MODF, MULD, MULF, NEGD, NEGF, SETD, SETF, SETI, SETL, STCDF, STCDF, STCDI, STCDL, STCFI, STCFL, STD, STEXP, STF, STFPS, STST, SUBD, SUBF, TSTD, TSTF.
The 16-bit architecture meant that a program had to fit within 64 Kb of memory for both data and instructions, although some models supported separate Instruction and Data space, allowing 64 Kb for each, per program, if the operating system allowed it.
Models
The PDP-11/20 was the first PDP-11 that DEC released, in 1970. The PDP-11/r20 was a ruggedized version in a rack-mount form. Both models used core memory and the UNIBUS. They were available as desktop or rack-mount systems.
The PDP-11/45 used the UNIBUS and had an integral FP11-C FPP. It could be configured with Core, MOS, or Bipolar memory. The PDP-11/55 was identical to a PDP-11/45 with Bipolar memory. The CPUs supported dual Instruction/Data space allowing programs to reach 128 Kb in size.
The PDP-11/60 had a KD11-K CPU and optional FP11-E FPP. It had MOS memory and a writable control store.
The PDP-11/70 was the top-end minicomputer of the PDP-11 line. It was a rack-mount system. The CPU cabinet weighed 500 lbs. It used the UNIBUS, MASSBUS, and MOS memory. The CPU supported dual Instruction/Data space allowing programs to reach 128 Kb in size.
The Micro/T-11, Micro/J-11, Micro/F-11, PDP-11/83, and PDP-11/84 all had a PDP-11 microprocessor CPU. The rest of the line has single or multi-board CPUs.
The PDP-11/74 was a multiprocessor system consisting of 4 PDP-11/70 CPUs. The development of the system was terminated before it was commercially released.
Comparison
The following is a comparison of the systems in the PDP-11 series, performance is the maximum performance (with bipolar RAM) relative to a standardized rating of 1:
| System_Model | Performance | Max memory | System Bus | Aggregate I/O |
| Micro/T-11 | LSI-11 | |||
| PDP-11/10 | ||||
| PDP-11/15 | 64 Kb | UNIBUS | ||
| PDP-11/34a | 248 Kb | UNIBUS | ||
| PDP-11/44 | 4 Mb | UNIBUS | ||
| PDP-11/45 | 248 Kb (4 Mb) | UNIBUS, MASSBUS | ||
| PSP-11/55 | = 11/45 | 248 Kb | UNIBUS | |
| PDP-11/03 | .03 | 28 Kb | QBUS | |
| PDP-11/05 | .07 | 28 Kb | UNIBUS | |
| PDP-11/04 | .08 | 56 Kb | UNIBUS | |
| PDP-11/20 | .09 | 64 Kb | UNIBUS | |
| PDP-11/r20 | .09 | 64 Kb | UNIBUS | |
| PDP-11/40 | .1 | UNIBUS | ||
| PDP-11/23 | .12 | 4 Mb | ||
| Micro/F-11 | .13 | 2 Mb | LSI-11 | |
| PDP-11/34 | .13 | 248 Kb (4 Mb) | UNIBUS | |
| PDP-11/24 | .15 | 4 Mb | ||
| PDP-11/53 | .3 | 4 Mb | QBUS | 3.3 |
| PDP-11/53+ | .36 | 4 Mb | QBUS | 3.3 |
| PDP-11/44 | .39 | 4 Mb | UNIBUS | |
| PDP-11/73 | .42 | 4 Mb | QBUS | 3.3 |
| Micro/J-11 | .6 | 2 Mb | LSI-11 | |
| PDP-11/70 | .6 | 4 Mb | UNIBUS, MASSBUS | 5.8 |
| PDP-11/83 | .72 | 4 Mb | QBUS | 3.3 |
| PDP-11/84 | .72 | 4 Mb | UNIBUS | |
| PDP-11/60 | .75 | 248 Kb | UNIBUS | |
| PDP-11/93 | .84 | |||
| PDP-11/74 | 2.4 (est) |
Software
DEC wrote a number of software products for the PDP-11 line. The operating systems included RSX-11, RT-11, MUMPS-11, IAS, and RSTS. User and development applications were also provided by DEC and third party companies.
Emulators
- SimH software (freeware)
- Ersatz-11 software emulator (both freeware/hobbyist and commercial versions)
- CHARON-11 software emulators
- StrobeData's PDP-11-on-a-board for your PC
- WinSoft Cobra-11 hardware emulator for the PDP-11
References
- PDP-11 Micro/PDP-11 Handbook, DEC, 1983
- PDP11/04/34a/44/60/70 Processor Handbook, DEC, 1979
- PDP11/04/34/45/55/60 Processor Handbook, DEC, 1978
- PDP 11/60 Processor Handbook, DEC, 1977
- PDP 11/70 Processor Handbook, DEC, 1976
- PDP 11/45 Processor Handbook, DEC, 1973
- PDP 11/34 Processor Handbook, DEC, 1976
- PDP11/20/15/r20 Processor Handbook, DEC, 1971
- PDP-11 Relative Performance
- The PDP-11