11/20, 11/15 born. Small Scale integration. 4 or 8k words mem, 28k max. (Some documentation referred to 32k max memory, but the top 4k was reserved for the I/O space. Machines with 28 KW core were rare, and most were shipped with 4 KW or 8 KW). Magnetic Core Memory. TTY ASR33 console. Papertape reader/punch typical I/O. Clock State cpu control. [All subsequent PDP-11 machines were to be microcoded]. The processor boards, all 15 of them (plus an optional line time clock, KW11-A), plugged into a 3 bank 4 x 6 slot backplane. Each 4 KW of memory occupied a further 4 x 6 slot backplane with some 12 modules. There was room in the 11" CPU drawer for three such additional backplanes. The MM11-E 4 KW memory module took 1.2us for a full memory cycle.
Q: Why does the 11/20 have 18 bit addresses on the UNIBUS but only a CPU capable of handling 16 address bits?
A: Because it was always intended to provide an MMU option to allow for extended addressing.
No matter what memory configurations, 16 bit, 18 bit or 22 bit were to be employed throughout the life of the PDP-11 family, the top 8 KB were always reserved for I/O addresses, registers, etc. In particular (initial list provided by Megan Gentry):
11/45. This was the first of the highspeed processors that begat 11/50, 11/55 and 11/70. 11/45 was microcoded, SSI/MSI, memory bus, core, MOS or bipolar memory. Max Memory 256 KB addressable via optional 18 bit Memory management unit. Optional Floating Point Unit. 11/55 had special bipolar high speed mem. Fast peripheral to memory slots Split I&D spaces. Introduced some extra instructions such as MUL, DIV, ASH, ASHC, SPL. The 11/45, /50 and /55 had the same CPU - the differences being in memory types, bus layouts, etc. The 11/70 was to have essentially the same cpu, with modifications to allow for Cache, 22-bit addressing and, for the first time, non-Unibus memory.
The PDP-11/45/50/55 had two Unibuses, normally joined by a single spaced jumper. The second Unibus has no arbitration, and was part of dual-ported fastbus memory. If you had fastbus memory (which made a 45 a 50 or 55), a second processor could access the memory. The only problem was that with the Unibus A and B split, DMA devices on Unibus A could not see the fastbus memory. I [not MMcC] had a PDP11/50 and PDP11/20 set up in such a fashion, with the PDP11/20 doing high speed A/D sampling and signal averaging using shared memory with the PDP11/50.
The fastbus memory is an independent high speed data bus internal to the 11/45 xx processors, with up to two solid state memory controllers and had each controller had two ports one for the CPU and the other available for a second Unibus where concievably a high speed DMA device could directly write to the memory. The DMA device on the `second' bus had to have a Unibus priority arbitration system, so you could in fact connect another CPU to it a bit like the DTS07's in concept. Note that, just to confuse the issue, this is not the same as the product/feature later marketed as FASTBUS.
KB-11 was the original /45 cpu, and used the FP-11 asynchronous FPP. Later machines under the /45 label were core memory /55s.
11/40, 11/35. Price same as 11/20, higher performance. (See tables and chart below for relative performance of the various PDP-11 processors) Small- and Medium-Scale Integration. Architecture of CPU like 11/45 without the raw power. Memory Management Unit, EIS/FIS Extended and Floating instruction sets as options. Introduced with Core memory, and later with MOS. Microcoded. Max Memory 256 KB. Extra instructions such as SOB XOR MARK SXT and RTT introduced. MUL, DIV etc implemented in the EIS option.
11/05, 11/10. Performance same as 11/20, lower price. Microcoded. 2-board processor. New 8 KW 3-board core memories were introduced with the /05 and /40. Later on, 16 KW memories were used before core got supplanted my MOS Memory. I remember these memories spec'd for a 980ns read/write cycle. I also remember the 11/05 CPU boards having the most green ECO wires I had ever seen on a machine. The cost of adding those wires manually must have, on reflection, added significantly to the cost of manufacture of the 11/05. Later board revisions eliminated these almost completely. It is interesting to consider that modern design, simulation and testing tools has virtually eliminated the ECO wire practice - a practice that we took for granted during the '70s and early '80s.
The /05 front panel has the following control switches:
LOAD ADRS EXAM CONT ENABLE/ START DEP HALT
When HALTed, the CONTinue key performed a single instruction per key depression (as do all the other 11's with front panels.)
There is a single 16 bit ADDR/DATA multiplexed display and a single RUN status light. The power switch has the following positions : OFF / POWER / PANEL LOCK.
11/70. CPU very similar to 11/45 in raw performance. Machine introduced with had core initially and MOS later. These machines introduced Cache, 22-bit Memory management of up to 4 MB. Optional Floating point processors. Massbus periperal controllers which had a direct path to memory first appeared on this machine. Note that MASSBUS (RH70's) adapters attached directly to memory were unique to the 11/70 -- MBAs only otherwise appeared on different series (PDP-10, VAX etc). Unibus systems could use MASSBUS peripherals, but the controllers (RH11's) spoke over the Unibus and lost most of the speed advantage. While this machine was not the fastest -11 (that title belongs to the bipolar memory equipped 11/55), no other -11 could approach the 11/70 in terms of I/O throughput over its multiple massbus/memory bus architecture.
The KB-11B was the original 70 cpu. Similar to the KB11 based 11/45, plus unbus map, 22-bit, MBCs etc. The 11/70 had the `feature' of the slowest bus of ANY -11. And when a UNIBUS peripheral did DMA, EVERYTHING stopped! This is one of the reasons the Seti upgrades are so good. They enable the RHs, CPU, and UNIBUS to all operate in parellel.
KB-11C: The FP-11 proved `featureful' in practice, and was replaced with a faster synchronous FP-11C. This required the `FP-11C compatible KB-11.'
The 11/70 was a 18 month overnight wonder to fill the gap left by the late development of the 32-bit wonder box! :-)
The C/D cpus used the FP-11C FPP. In fact, the KB-11C is referred to as the `FP-11C compatible KB-11' in some manuals.
LSI-11, first of the microprocessor -11s, implemented on 4 chips. It was sold by Western Digital as the WDC-16. First of the Q-bus machines (All others above were UNIBUS). Implemented on a single quad height board. Performance approximately equalled that of the 11/05. Minimal size. Aimed at OEM embedded controllers, etc.
11/03 Same microprocessor as 11/2. Performance the same as the 11/05, but priced much less. Qbus. More expandable than LSI-11/2. Aimed at low end of 11/05 market.
11/04. UNIBUS. There are conflicting reports about this model. One is that it was a replacement for the 11/05, with the same performance, but priced much less. Standard TTL and STTL logic. It only used one cpu board instead of the 11/05's two. The other version is that it was a "reduced" version of the 11/34, with 16-bit addressing, no cache, no FPP option, etc. It was designed by the same person as the /34, and it fitted on one UNIBUS board. Apparently introduced in 1978?
11/34. Follow-on to 11/40 with same performance at lower cost. Two board cpu in SSI/MSI TTL. Initially had a two-switch KY11-LA front panel (Halt&Boot). Optional calculator-style Octal KY11-LB front panel later, although most customers opted to have this as time progressed. The KY11-LB could be used to singlestep or microstep a program for diagnostic use. The /34 style memory managment was 18 bit and the memory management was standard.
KB-11D The 18 bit version of the C. used in /55s and very late /45s. I think all /50s were KB-11 cpu's. (PaulR)
The big difference between a /50 and a /55 is the /55 is a KB-11D, not a KB-11 cpu:
LSI-11/2 (11/21?) KD11-HA. Double height module follow-on to LSI-11. Performance of an 11/05, but priced much less. Qbus. Lacks onboard memory and WCS chip socket. Basically the same chipset. Both used in PDP-11/03 systems. LSI-11 sucks more power than the LSI-11/2.
The LSI-11/2 chipset was simply "the LSI-11 chipset," manufactured by WDC for DEC. FIS/EIS upgrade microms (MICrocode ROMS) were available for the LSI-11, and at least on the PDT-11s there was a special 2-in-1 version of the regular CPU microms that would free up a socket for the FIS/EIS microm.
11/60. Intended follow-on to 11/40 at the high end/same price. Higher performance. Writable control store for custom instructions. Cache and ECC MOS memory. Too costly, too late. Memory management was 18 bit and standard. Floating point instructions were standard - but implemented by the CPU microcode. There was a floating point coprocessor option. The 60 was to have been a 22 bitter originally.
11/34a, 11/34c. The /34a with the "right cache" presented a higher level of performance than the then "hot machine" of the time - I believe it was the /60 - in the eyes of -11 engineering / central engineering. The "c" upgrade was the re-establishment of the original cache. Thus, the /34c was an internal mythical model to allow FS to keep track of what systems had the upgrade - much like the /35 vs /40 clock mod that made the /35 faster.
PDT family. PDT 11/110, 11/130, 11/150. The PDT-11/110 and -11/130 were built into the cardcage of a VT100 (along with the terminal). The 11/110 simply had code to allow down-loading of the PDP-11. It had no peripherals. The 11/130 had two TU58's mounted just under the monitor. The PDT-11/150 was built into a table-top unit which also had two RX01 equivalent drives, and the cpu board was built into the the Floppy box. The PDT-150 had separate VT100 and systems box. The system box for the single disk unit: 51.0 cm (20.08 in) length X 33.02 cm (13.0) width X 20.9 cm (8.23 in) height and 33 pounds. Dual disk unit: same, but 34.8 cm (13.42 in) height and 46 pounds. The box slopes to the front and has a small front panel that reads `digital PDT-11' and has four LEDs ("1", "2", "RUN", "POWER"). LED 1 Lights to indicate a system error when in the self-test mode. LED 2 lights to indicate that the system is waiting for an autobaud response from the console terminal. Otherwise both can be controlled by a user program. The top of the case is plastic and is held fast by two screws; undoing these allows access to the CPU and logic. Two RX01 drives (8.5" floppies) are mounted in the bottom 75% of the cabinet. There are three terminal ports, one console port, one printer port, and one modem port. The 3 terminal ports are optional. All of the connectors, save for the modem port, are female DB25 connectors, which I have been told is rare. Depending upon the version of RT-11 being used, the machine expects either VT52 or VT100 console/terminal input -- I believe that versions prior to 4.0 default to VT52. The stock memory appears to be about 30K words (not including the I/O page). It is also noteworthy that the RX01 firmware is suspected of not being strictly "real" RX01. The PDT will write fresh single-density formatting every time it writes to the disk. It's also interesting to note that the physical device name for the drives is PD: instead of DX: The documentation calls the drive controller an RXT-11. It also claims that a PDP11/V03 with RXV11 is compatible with the PDT11/150. The print set shows 27 sectors/track for the PDT. The RX02 User's Guide shows 26 sec./trk.
All three PDT's had the equivalent of an 11/2 (same chip set, in fact) and 60 KB addressable (rather than 56 KB, since it had only a 4 KB I/O page) These machines, running RT11, could be viewed as being the forerunners of today's PCs. They were never marketed as such, and thus faded into obscurity. Although there is no I/O bus, per se, the print set gives the controller card equivalent for the on-board circuits:
A useful table from the PDT-11/150 User Guide:
PDT-11/15x-yz x is console terminal: 0 NONE 1 VT100-AA, VT100-AB 2 LA120-AA, LA120-BA, LA120-DA 3 LA34-DA, LA34-HA 4 LS210-HE, LS210-HJ 5 LA36-HE, LA36-HJ
11/44. Successful follow-on to 11/40 high end/11/70 low end. Almost 11/70 power at 11/40 price. UNIBUS. Also, it could have the CIS option. The front-end processor on this system was built around the Intel 8085. Lacked the dual register set of the 11/70.
11/23. Successful follow-on to 11/03. Single F(onz)-11 chip. 11/34-ish performance at lower cost. Qbus. F11 chip does 22 bit addressing, but only 18 address lines brought out in earliest versions; all 22 brought out on later revs of the KDF11-A.
11/24. successful follow-on to 11/04, 11/34. F-11 (Fonz) chip. Price of 11/04, performance of 11/34. The 11/23 and /24 had the 11/34 style memory management. They both had 22 bit addressing, but for the /24, the UNIBUS map (to map 18-bit UNIBUS DMA addresses onto the 22 bit memory address) was a (rather rare) option called, I believe, a KT24.
The T-11 (Tiny) is a similar architecture to the LSI-11 on a single 40-pin DIP that was primarily intended for the embedded market. It was used only in the Falcon SBC-11/21 and a few controllers (e.g. RQDX3, DEUNA, LA-120). The T-11 was also used in the KXT11-CA Quad width `communications processors' that allowed you to have multiple CPU's on the Qbus. One cancelled DEC project used it as a cpu/controller inside a telephone (with keyboard, video, etc).
PRO-350, PRO-325. This machine was released as one of a triumvirate of PCs by DEC. The PCs consisted of the DECmate-II PDP-8/WPS based dedicated word processor; the 8080/8086 based Rainbow, and the F-11 based PRO-325/350. Although the machines were well engineered, they were not successful in the marketplace for a number of reasons. First, the customer base was confused by being offered three totally separate, incompatible offerings. Second, the Rainbow, although able to run both CP/M and MS/DOS, was incompatible in both hardware and software with the IBM PC that was establishing the defacto standards for the industry. And third, the PRO-350 was based on a bounded, restricted version of RSX11, and was viewed as an oddity in the marketplace.
The PRO-325 was the same as a PRO-350, but it only had the RX50's in it; the PRO-350 also had an RD-series hard drive (originally an RD50, but with newer controllers you could have up to an RD52). The PRO-380 was the same as the PRO-350 with respect to devices. All three had a bitmap display. The PRO-325/350 was based on the F-11 (11/23) chip set. The PRO-380 was based on the J-11 (Jaws, 11/73) chip. They all were desktop units, though an option allowed them to be mounted in a tower configuration.
Note on the Pro 380: one reason for its failure was its bad performance. It ran the J-11 at only 10 MHz. Reason was a design mistake: the entire system has only one clock, 20 MHz, for everything from CPU to video to UART baud rates. J-11 was planned to do 20 MHz, fab only got it to 18, but the design didn't allow for a separate CPU clock so the Pro had to go all the way down to 10.
PRO-380. This was an upgrade to the PRO-350, using the J-11 chipset. The market opportunity was closed to it at this time, and they only had limited success. The PRO-350/380 probably saw most use as console devices/frontends for a number of the VAX8000 series machines.
In the following sections, quotes marked [-PSH] are extracts from the 1987 "PDP-11 Systems Handbook"
11/73, Follow-on to 11/23, 11/24. J(aws)-11 chip. Similar cost, higher performance. Replacement for 11/44.
The MicroPDP-11/73 computer provides one-third more compute power than the MicroPDP-11/53, ... 15-megahertz J-11 chip ... Memory is expandable in 1- and 2-Mbyte increments .... [-PSH]
11/73 is the KDJ11-A or KDJ11-B. (The -B just puts things like the console SLU and boot roms onto one board; some revs also have PMI memory ... the boundary between the 11/73 and 11/83 is a bit fuzzy...). There was never a UNIBUS equivalent of the /73. The /73 didn't replace either the /44 or the /70. (Nothing replaced the 11/70! Nothing else had the I/O throughput, and the CPU was only just outrun by the 11/83 / 11/84.)
11/83, 11/84 Higher performance versions of 11/73.
The computing power of the MicroPDP-11/83 has twice the performance of the MicroPDP-11/73 .... The MicroPDP-11/83, by combining an 18-megahertz J-11 chip and a companion floating-point accelerator chip with a new private memory interconnect on one module, .... [-PSH].
The MicroPDP-11s (11/23+, /73 and /83) were in a tower configuration which could be configured for desktop use, or the innards removed and rack-mounted. (The differences between the /73 and the /83 were simply:
The 11/8x can't go much above 18 MHz. While the original design called for 20 MHz, neither the J11's nor the gate arrays were up to it. They use Private Memory Interconnect (PMI) much like the 11/70 did years earlier. The memory (for the /83) lives in the usual PMI slots, and then a bus adapter brings the bus out to the UNIBUS. DEC realized that they had a lot of customers with UNIBUS peripherals, but they didn't want to build another UNIBUS processor (the previous one being the 11/24), so they expanded on the 11/24 + KT-24 concept and came up with the 11/84. It was mostly UNIBUS, but the first slots were QBUS (so it could use the KDJ11-B boards used in the 11/83), followed by a QBUS-UNIBUS adaptor. Considering that at that time, all DEC had on the Qbus was the RD-series and the KDA50 which started out as a real power pig, UNIBUS was the way to go if you wanted a system with big (but genuine DEC) disks and high-end tapes.
An alternate viewpoint from Don Stokes:
I'm not sure I agree re the peripherals for the 11/8x and onward. The KDA50 was a pig, but so was the UDA50, and by then DEC weren't selling anything but RAxx drives as "big" disks. Tapes were always a problem, but the TU81 was available by the mid 80s, and the TS05 was also available. I got the distinct feeling that the 11/84 was aimed at upgrades and additions for sites with a heavy UNIBUS investment rather than for new systems/sites. After all, burst mode made the Qbus faster than the UNIBUS, the boxes were smaller and much less power hungry. (KDA50 notwithstanding -- KDA50s inevitably got put in an expansion chassis because of the power. But at least the expansion box could hold 5.25" drives as well.) I never could understand why DEC abandoned dedicated peripheral controllers in favour of the UDA50. We used to get much more throughput (commercial loads) out of 11/70s with RP06s and RM05s than we ever could with RA81/UDA50 equipped 11/750s running the same applications. 11/44s seemed similarly handicapped.
11/53. Essentially a stripped down /73. KDJ11-D I think -- J11 chip, 15MHz, lacked cache or FPA options, has (slowish) onboard memory. There wasn't a /54.
The heart of the MicroPDP-11/53 is a 15-megahertz, J-11 single board computer with 0.5 Mbytes of onboard memory ... The MicroPDP-11/53 PLUS supermicrosystem ... has an additional 1 Mbyte of memory for a total of 1.5 Mbytes of onboard memory. [-PSH]
11/93, 11/94 Possibly the last PDP, they're just the 83/84 CPU board with a higher clock speed. The 11/93 and /94 are a new design which uses the J11 CPU. Instead of cache, the entire main memory (2 or 4 MB) is on-board w/ 70 ns parts. A new memory controller gate array lets the CPU at the memory during NPR transfers (even during block mode). A Z80 CPU controls 8 emulated DL ports (this subsystem is called a DLV22) with buffering, etc. The board uses the same 18 MHz DCJ11-AE as the 11/8x - all the speed improvements are from a more modern board design. The 11/9x will go above 18 MHz.
DEC marketing material:
The PDP-11/94 is the newest and most powerful member of the PDP-11 family of multiuser systems. The PDP-11/94 features a new, performance-enhanced processor that combines the DCJ11/FPJ11 chip sets with 2 Mbyte or 4 Mbyte of high-speed onboard memory, eight buffered, programmable asynchronous serial lines and a time of year clock. The single-board implementation of the processor effectively complements the configuration flexibility and expansion capacity of enhanced UNIBUS systems packaging.
- A new performance-enhanced single-board CPU features Digital's C-MOS 18 MHz J-11 chipset, FPJ-11 coprocessor, parity memory, and eight buffered serial lines
- The full PDP-11 instruction set including floating-point and EIS instructions, plus an integral floating-point coprocessor
- Sophisticated 22-bit memory management, dual register set, separate instruction and data space, and three system modes: kernel, supervisor, and user
- 2 or 4 Mbyte of onboard high-density parity memory
- Private Memory Interconnect (PMI) architecture for high-speed data transfers and enhanced system performance
- 64 Kbyte bootstrap/diagnostic ROM facility and 8-Kbyte EEPROM (100% diagnostic coverage)
- Program-controlled line-frequency clock
- Eight-line buffered programmable EIA/CCITT serial-line asynchronous interface
- ASCII console logic for system control and debugging
- Time of year clock
- Full battery backup support available
- Concurrent processing that allows the simultaneous execution of instructions and DMA transfers
- New compact design that requires less power and offers more expansion capacity and configuration flexibility
- Consistent UNIBUS systems packaging: standard 10.5 inch by 19 inch rackmount design center, H9642- and H9645-based systems cabinets
- Board-Level upgrade packages for installed PDP-11/84s