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PDP-10 KI10 Processor Simulator User's Guide

Revision of 22-Oct-2022

Copyright Notice

The SIMH source code and documentation is made available under a X11-style open source license; the precise terms are available at:

https://github.com/open-simh/simh/blob/master/LICENSE.txt

The DEC PDP-10/KI10 simulator was written by Richard Cornwell.

Table of Contents

1. Introduction

2. Simulator Files

3. KI10 Features

3.1 CPU

3.1.1 DDC10 Drum controller for TENEX

3.2 Unit record I/O Devices

3.2.1 Console Teletype (CTY) (Device 120)

3.2.2 Paper Tape Reader (PTR) (Device 104)

3.2.3 Paper Tape Punch (PTP) (Device 100)

3.2.4 Card Reader (CR) (Device 150)

3.2.5 Card Punch (CP) (Device 110)

3.2.6 Line Printer (LPT) (Device 124)

3.2.7 Type 340 Graphics display (DPY) (Device 130)

3.2.8 DK10 Timer Module (DK) (Device 070)

3.2.9 TM10 Magnetic Tape (MTA) (Device 340,344)

3.2.10 TD10 DECtape (DT) (Device 320,324)

3.3 Disk I/O Devices

3.3.1 FHA Disk Controller (Device 170)

3.3.2 DPA/DPB Disk Controller (Device 250/254)

3.3.3 DDC10 Drum controller for TENEX

3.4 Massbus Devices

3.4.1 RP Disk drives

3.4.2 RS Disk drives

3.4.3 TU Tape drives.

3.4.4 DC10E Terminal Controller (Device 240)

3.5 Network Devices

3.5.1 IMP Interface Message Processor (Device 460)

4. Symbolic Display and Input

Introduction

Originally the DEC PDP-10 computer started as the PDP-6. This was a 36 bit computer that was designed for timesharing, which was introduced in 1964. The original goal of the machine was to allow for processing of many 6 bit characters at a time. 36 bits were also common in machines like the IBM 7090, GE 645, and Univac 11xx lines. Several influences shaped the design of the PDP-6, including CTSS, Lisp, and support for larger memory.

The PDP-6 was canceled by DEC due to production problems. The engineers designed a smaller replacement, which happened to be a 36 bit computer that looked very much like the PDP-6. This was called the PDP-10, later renamed to "DECSystem-10". The system supported up to 256K 36-bit words of memory.

The first PDP-10 was labeled KA10, and added a few instructions to the PDP-6. Both the PDP-6 and PDP-10 used a base and limit relocation scheme. The KA10 generally offered two registers, one for user data and the second for user shared code. These were referred to as the Low-Segment and High-Segment. The High-Segment could be shared with several jobs.

The next version was called KI10 for Integrated. This added support for paging and double precision floating point instructions. It also added 4 sets of registers to improve context switching time. It could also support up to 4 megawords of memory.

Following the KI10 was the KL10 (for Low-Cost). The KL10 added double precision integer instructions and instructions to improve COBOL performance. This was the first version which was microcoded. The KL10 was extended to support user programs larger than 256K.

The final version to make it to market was the KS10 (for Small). This was a bit-slice version of the PDP-10 which used Unibus devices which were cheaper than the KL10 devices.

The original operating system for the PDP-6/PDP-10 was just called "Monitor". It was designed to fit into 6K words. Around the third release swapping was added. The sixth release saw the addition of virtual memory. Around the fourth release it was given the name "TOPS-10". Around this time BBN was working on a paging system and implemented it on the PDP-10. This was called "TENEX". This was later adopted by DEC and became "TOPS-20".

During the mid 1960s a group at MIT, who were not happy with how Multics was being developed, decided to create their own operating system, which they called Incompatible Timesharing System, or "ITS". The name was a play on an earlier project called the Compatible Timesharing System, or "CTSS". CTSS was implemented by MIT on their IBM 7090 as an experimental system that allowed multiple time sharing users to co-exist on the same machine running batch processing, hence the term "Compatible".

Also during the mid 1960s a group at Stanford Artificial Intelligence Laboratory (SAIL), started with a version of TOPS-10 and heavily modified it to become WAITS.

During the 1970s, Tymshare modified TOPS-10 to support random access files, paging with working sets, and spawnable processes. This ran on the KI10, KL10, and KS10.

The PDP-10 was ultimately replaced by the VAX.

Simulator Files

To compile the DEC PDP-10/KI10 simulator, you must define USE_INT64 as part of the compilation command line.

Subdirectory File Contains
PDP10/
kx10_defs.h KA10 simulator definitions
kx10_cpu.c KI10 CPU.
kx10_df.c DF10/C controller.
kx10_rh.c RH10 controller.
kx10_disk.h Disk formatter definitions
kx10_disk.c Disk formatter routine.
kx10_sys.c KI10 System interface
kx10_cty.c Console Terminal Interface.
kx10_pt.c Paper Tape Reader and Punch
kx10_rc.c RC10 Disk controller, RD10 and RM10 Disks
kx10_dp.c RP10 Disk controller, RP01/2/3 Disks.
kx10_rp.c RH10 Disk controller, RP04/5/6 Disks.
kx10_rs.c RH10 Disk controller RS04 Fixed head Disks.
kx10_dt.c TD10 DECtape controller.
kx10_mt.c TM10A/B Magnetic tape controller.
kx10_tu.c RH10/TM03 Magnetic tape controller.
kx10_lp.c Line printer.
kx10_cr.c Punch card reader.
kx10_cp.c Punch card punch.
kx10_dk.c DK10 interval timer.
kx10_dc.c DC10 communications controller.
kx10_ddc.c DDC-10 Drum controller
kx10_lights.c Front panel interface.
kx10_imp.c IMP10 interface to ethernet.

KI10 Features

The KI10 simulator is configured as follows:

Device Name(s) Simulates
CPU KI10 CPU with 256KW of memory
CTY Console TTY.
PTP Paper tape punch
PTR Paper tape reader.
LPT LP10 Line Printer
CR CR10 Card reader.
CP CP10 Card punch
MTA TM10A/B Tape controller.
DPA,DPB RP10 Disk controller
FSA RS04 Disk controller via RH10
RPA,RPB,RPC,RPD RH10 Disk controllers via RH10
PMP PMP IBM 3330 disk controller
TUA TM02 Tape controller via RH10
FHA RC10 Disk controller.
DDC DDC10 Disk controller.
DT TD10 DECtape Controller.
DC DC10 Communications controller.
DK Clock timer module.
IMP IMP network interface

CPU

The CPU options include setting memory size.

command action
SET CPU 16K Sets memory to 16K
SET CPU 32K Sets memory to 32K
SET CPU 48K Sets memory to 48K
SET CPU 64K Sets memory to 64K
SET CPU 96K Sets memory to 96K
SET CPU 128K Sets memory to 128K
SET CPU 256K Sets memory to 256K
SET CPU 512K Sets memory to 512K
SET CPU 768K Set memory to 768K
SET CPU 1024K Set memory to 1024K
SET CPU 2048K Set memory to 2048K
SET CPU 4096K Set memory to 4096K
SET CPU SERIAL=val Set serial number of system. (default: 514)
SET CPU DF10 Set DF10 emulation to model A, max 256K memory.
SET CPU DF10C Set DF10 emulation to model C, no max.
SET CPU NOMAOFF Sets traps to default of 040
SET CPU MAOFF Move trap vectors from 040 to 0140
SET CPU NOIDLE Disables Idle detection
SET CPU IDLE Enables Idle detection

CPU registers include the visible state of the processor as well as the control registers for the interrupt system.

Name Size Comments
PC 18 Program Counter
FLAGS 18 Flags
FM0-FM17 36 Fast Memory
SW 36 Console SW Register
MI 36 Memory Indicators
AS 18 Console AS register
ABRK 1 Address break
ACOND 5 Address Condition switches
PIR 8 Priority Interrupt Request
PIH 8 Priority Interrupt Hold
PIE 8 Priority Interrupt Enable
PIENB 1 Enable Priority System
BYF5 1 Byte Flag
UUO 1 UUO Cycle
PUSHOVER 1 Push overflow flag
MEMPROT 1 Memory protection flag
NXM 1 Non-existing memory access
CLK 1 Clock interrupt
OV 1 Overflow enable
FOV 1 Floating overflow enable
APRIRQ 3 APR Interrupt number
CLKIRQ 3 CLK Interrupt number
UB 18 User Base Pointer
EB 18 Executive Base Pointer
FMSEL 8 Register set select
SERIAL 10 System Serial Number
INOUT 1
SMALL 1
PAGE_ENABLE 1 Paging enabled
PAGE_FAULT 1 Page fault
AC_STACK 18 AC Stack
PAGE_RELOAD 18 Page reload
FAULT_DATA 36 Page fault data
TRP_FLG 1 Trap flag

The CPU can maintain a history of the most recently executed instructions.

This is controlled by the SET CPU HISTORY and SHOW CPU HISTORY commands:

command action
SET CPU HISTORY clear history buffer
SET CPU HISTORY=0 disable history
SET CPU HISTORY=n enable history, length = n
SHOW CPU HISTORY print CPU history
SHOW CPU HISTORY=n print first n entries of CPU history

Instruction tracing shows the Program Counter, the contents of AC selected, the computed effective address. AR is generally the contents the memory location referenced by EA. RES is the result of the instruction. FLAGS shows the flags after the instruction is executed. IR shows the instruction being executed.

Unit Record I/O Devices

Console Teletype (CTY) (Device 120)

The console station allows for communications with the operating system.

command action
SET CTY 7B 7 bit characters, space parity.
SET CTY 8B 8 bit characters, space parity.
SET CTY 7P 7 bit characters, space parity.
SET CTY UC Translate lower case to upper case.

The CTY also supports a method for stopping the TOPS-10 operating system.

command action
SET CTY STOP Deposit 1 in location 30.

Paper Tape Reader (PTR) (Device 104)

Reads a paper tape from a disk file.

Paper Tape Punch (PTP) (Device 100)

Punches a paper tape to a disk file.

Card Reader (CR) (Device 150)

The card reader (CR) reads data from a disk file. Card reader files can either be text (one character per column) or column binary (two characters per column). The file type can be specified with a set command:

command action
SET CRn FORMAT=TEXT Sets ASCII text mode
SET CRn FORMAT=BINARY Sets for binary card images.
SET CRn FORMAT=BCD Sets for BCD records.
SET CRn FORMAT=CBN Sets for column binary BCD records.
SET CRn FORMAT=AUTO Automatically determines format.

or in the ATTACH command:

command action
ATTACH CRn <file> Attaches a file
ATTACH CRn -f <format> <file> Attaches a file with the given format.
ATTACH CRn -s <file> Added file onto current cards to read.
ATTACH CRn -e <file> After a file is read in, the reader will receive an end-of-file flag.

Card Punch (CP) (Device 110)

The card punch (CP) writes data to a disk file. Cards are simulated as ASCII lines with terminating newlines. Card punch files can either be text (one character per column) or column binary (two characters per column). The file type can be specified with a set command:

command action
SET CP FORMAT=TEXT Sets ASCII text mode
SET CP FORMAT=BINARY Sets for binary card images.
SET CP FORMAT=BCD Sets for BCD records.
SET CP FORMAT=CBN Sets for column binary BCD records.
SET CP FORMAT=AUTO Automatically determines format.

or in the ATTACH command:

command action
ATTACH CP <file> Attaches a file
ATTACH CP -f <format> <file> Attaches a file with the given format.

Line Printer (LPT) (Device 124)

The line printer (LPT) writes data to a disk file as ASCII text with terminating newlines. It currently handles standard signals that control paper advance.

command action
SET LPTn LC Allow printer to print lower case
SET LPTn UC Print only upper case
SET LPTn UTF8 Print control characters as UTF8 characters.
SET LPTn LINESPERPAGE=n Sets the number of lines before an auto form feed is generated. There is an automatic margin of 6 lines. There is a maximum of 100 lines per page.
SET LPTn DEV=n Sets device number to n (octal).

These characters control the skipping of various number of lines.

Character Effect
014 Skip to top of form.
013 Skip mod 20 lines.
020 Skip mod 30 lines.
021 Skip to even line.
022 Skip to every 3 line
023 Same as line feed (12), but ignore margin.

Type 340 Graphics Display (DPY) (Device 130)

Primarily useful under ITS, TOPS-10 does have some limited support for this device. By default this device is not enabled. When enabled and commands are sent to it, a graphics window will display.

DK10 Timer Module (DK) (Device 070)

The DK10 timer module does not have any settable options.

TM10 Magnetic Tape (MTA) (Device 340,344)

The TM10 was the most common tape controller on KA10 and KI10. The TM10 came in two models, the TM10A and the TM10B. The B model added a DF10 which allowed the tape data to be transferred without intervention of the CPU. The device has 2 options.

command action
SET MTA TYPE=t Sets the type of the controller to A or B

Each individual tape drive supports several options: MTA is used as an example.

command action
SET MTAn 7T Sets the magtape unit to 7 track format.
SET MTAn 9T Sets the magtape unit to 9 track format.
SET MTAn LOCKED Sets the magtape to be read only.
SET MTAn WRITEENABLE Sets the magtape to be writable.

TD10 DECtape (DT) (Device 320,324)

The TD10 was the standard DECtape controller for KA and KIs. This controller loads the tape into memory and uses the buffered version. Each individual tape drive supports several options: DT is used as an example.

command action
SET DTn LOCKED Sets the DECtape to be read only.
SET DTn WRITEENABLE Sets the DECtape to be writable.
SET DTn 18b Default, tapes are considered to be 18bit tapes.
SET DTn 16b Tapes are converted from 16 bit to 18bit.
SET DTn 12b Tapes are converted from 12 bit to 18bit.

Disk I/O Devices

The PDP-10 supported many disk controllers.

FHA Disk Controller (Device 170)

The RC10 disk controller used a DF10 to transfer data to memory. There were two types of disks that could be connected to the RC10 the RD10 and RM10. The RD10 could hold up to 512K words of data. The RM10 could hold up to 345K words of data.

Each individual disk drive supports several options: FHA is used as an example.

command action
SET FHAn RD10 Sets this unit to be an RD10.
SET FHAn RM10 Sets this unit to be an RM10.
SET FHAn LOCKED Sets this unit to be read only.
SET FHAn WRITEENABLE Sets this unit to be writable.

DPA/DPB Disk Controller (Device 250/254)

The RP10 disk controller used a DF10 to transfer data to memory. There were three types of disks that could be connected to the RP10 the RP01, RP02, RP03. The RP01 held up to 1.2M words, the RP02 5.2M words, RP03 10M words. The second controller is DPB. Disks can be stored in one of several file formats, SIMH, DBD9, and DLD9. The later two are for compatibility with other simulators.

Each individual disk drive supports several options: DPA is used as an example.

command action
SET DPAn RP01 Sets this unit to be an RP01.
SET DPAn RP02 Sets this unit to be an RP02.
SET DPAn RP03 Sets this unit to be an RP03.
SET DPAn HEADERS Enables the RP10 to execute write headers function.
SET DPAn NOHEADERS Prevents the RP10 to execute write headers function.
SET DPAn LOCKED Sets this unit to be read only.
SET DPAn WRITEENABLE Sets this unit to be writable.

To attach a disk use the ATTACH command:

command action
ATTACH DPAn <file> Attaches a file
ATTACH DPAn -f <format> <file> Attaches a file with the given format.
ATTACH DPAn -n <file> Creates a blank disk.

Format can be SIMH, DBD9, or DLD9.

DDC10 Drum controller for TENEX

The DEC RES-10 drum controller is used by TENEX for swapping. This device is disabled by default.

Massbus Devices

Massbus devices are attached via RH10’s. Devices start a device 270 and go up (274, 360, 364, 370, 374). For TOPS-10, devices need to be in the order RS, RP, TU. By default RS disks are disabled. The first unit which is not enabled will get device 270, units will be assigned the next available address automatically. The device configuration must match that which is defined in the OS.

RP Disk Drives

Up to 4 strings of up to 8 RP drives can be configured. By default the third and fourth controllers are disabled. These are addresses as RPA, RPB, RPC, RPD. Disks can be stored in one of several file formats, SIMH, DBD9, and DLD9. The later two are for compatibility with other simulators.
SET RPAn RP04 Sets this unit to be an RP04 (19MWords)
SET RPAn RP06 Sets this unit to be an RP06 (39MWords)
SET RPAn RP07 Sets this unit to be an RP07 (110MWords)
SET RPAn LOCKED Sets this unit to be read only.
SET RPAn WRITEENABLE Sets this unit to be writable.

To attach a disk use the ATTACH command:
ATTACH RPAn <file> Attaches a file
ATTACH RPAn -f <format> <file> Attaches a file with the given format.
ATTACH RPAn -n <file> Creates a blank disk.

Format can be SIMH, DBD9, or DLD9.

RS Disk Drives

One string of up to 8 RS drives can be configured. These drives are fixed head swapping disks. By default they are disabled.
SET FSAn RS03 Sets this unit to be an RS03 (262KWords)
SET FSAn RS04 Sets this unit to be an RS04 (262KWords)
SET FSAn LOCKED Sets this unit to be read only.
SET FSAn WRITEENABLE Sets this unit to be writable.

TU Tape Drives

The TUA is a Massbus tape controller using a TM03 formatter. There can be one per RH10 and it can support up to 8 drives.
SET TUAn LOCKED Sets the mag tape to be read only.
SET TUAn WRITEENABLE Sets the mag tape to be writable.

DC10E Terminal Controller (Device 240)

The DC device was the standard terminal multiplexer for the KA10 and KI10’s. Lines came in groups of 8. For modem control there was a second port for each line. These could be offset by any number of groups.

command action
SET DC LINES=n Set the number of lines on the DC10, multiple of 8.
SET DC MODEM=n Set the start of where the modem control DEC10E lines begins.

All terminal multiplexers must be attached in order to work. The ATTACH command specifies the port to be used for Telnet sessions:

command action
ATTACH <device> <port> Set up listening port

where port is a decimal number between 1 and 65535 that is not being used for other TCP/IP activities.

Once attached and the simulator is running, the multiplexer listens for connections on the specified port. It assumes that any incoming connection is a Telnet connection. The connections remain open until disconnected either by the Telnet client, a SET <device> DISCONNECT command, or a DETACH <device> command.

command action
SET <device> DISCONNECT=n Disconnect line n

The <device> implements the following special SHOW commands:

command action
SHOW <device> CONNECTIONS Displays current connections to the <device>
SHOW <device> STATISTICS Displays statistics for active connections
SHOW <device> LOG Display logging for all lines.

Logging can be controlled as follows:

command action
SET <device> LOG=n=filename Log output of line n to filename
SET <device> NOLOG Disable logging and close log file

Network Devices

IMP Interface Message Processor (Device 460)

This allows the KA/KI to connect to the Internet. Currently only supported under ITS. ITS and other OSes that used the IMP did not support modern protocols and typically required a complete rebuild to change the IP address. Because of this the IMP processor includes built in NAT and DHCP support. For ITS the system generated IP packets which are translated to the local network. If the HOST is set to 0.0.0.0 there will be no translation. If HOST is set to an IP address then it will be mapped into the address set in IP. If DHCP is enabled the IMP will issue a DHCP request at startup and set IP to the address that is given. By default this device is not enabled.

command action
SET IMP MAC=xx:xx:xx:xx:xx:xx Set the MAC address of the IMP to the value given.
SET IMP IP=ddd.ddd.ddd.ddd/dd Set the external IP address of the IMP along with the net mask in bits.
SET IMP GW=ddd.ddd.ddd.ddd Set the Gateway address for the IMP.
SET IMP HOST=ddd.ddd.ddd.ddd Sets the IP address of the PDP-10 system.
SET IMP DHCP Allows the IMP to acquire an IP address from the local network via DHCP. Only HOST must be set if this feature is used.
SET IMP NODHCP Disables the IMP from making DHCP queries
SET IMP DHCPIP=ddd.ddd.ddd.ddd The address of the DHCP server, generally this is for display only.
SET IMP MIT Sets the IMP to look like the IMP used by MIT for ITS.
SET IMP BBN Sets the IMP to behave like generic BBN IMP. (Not implemented yet).
SET IMP WAITS Sets the IMP for Stanford style IMP for WAITS.

The IMP device must be attached to a TAP or NAT interface. To determine which devices are available use the SHOW ETHERNET to list the potential interfaces. Check out the Readme_ethernet.txt from the doc directory.

The IMP device can be configured in several ways. Either it can connect directly to an ethernet port (via TAP) or it can be connected via a TUN interface. If configured via TAP interface the IMP will behave like any other ethernet interface and if asked obtain its own address. In environments where this is not desired the TUN interface can be used. When configured under a TUN interface the simulated network is a collection of ports on the local host. These can be mapped based on configuration options, see the 0readme_ethernet.txt file as to options.

With the IMP interface, the IP address of the simulated system is static, and under ITS is configured into the system at compile time. This address should be given to the IMP with the SET IMP HOST=<ip>, the IMP will direct all traffic it sees to this address. If this address is not the same as the address of the system as seen by the network, then this address can be set with SET IMP IP=<ip>, and SET IMP GW=<ip>, or SET IMP DHCP which will allow the IMP to request an address from a local DHCP server. The IMP will translate the packets it receives and sends to look like they appeared from the desired address. The IMP will also correctly translate FTP requests in this configuration.

When running under a TUN interface, IMP is on a virtual 10.0.2.0 network. The default gateway is 10.0.2.1, with the default IMP at 10.0.2.15. For this mode DHCP can be used.

Symbolic Display and Input

The KI10 simulator implements symbolic display and input. These are controlled by the following switches to the EXAMINE and DEPOSIT commands:

switch action
-v Looks up the address via translation, will return nothing if address is not valid.
-u With the -v option, use user space instead of executive space.
-a Display/Enter ASCII data.
-p Display/Enter packed ASCII data.
-c Display/Enter Sixbit character data.
-m Display/Enter symbolic instructions.
default Display/Enter octal data.

Symbolic instructions can be of the formats:

  • opcode ac, operand
  • opcode operands
  • i/o_opcode device, address

Operands can be one or more of the following in order:

  • Optional @ for indirection.
  • + or - to set sign.
  • Octal number
  • Optional (AC) for indexing.

Breakpoints can be set at real memory address. The PDP-10 supports three types of breakpoints. Execution, Memory Access and Memory Modify. The default is Execution. Adding -R to the breakpoint command will stop the simulator on access to that memory location, either via fetch, indirection or operand access. Adding -w will stop the simulator when the location is modified.

The simulator can load RIM files, SAV files, EXE files, WAITS octal DMP files, and MIT SBLK files.

When instruction history is enabled, the history trace shows internal status of various registers at the start of the instruction execution.

field meaning
PC Shows the PC of the instruction executed.
AC The contents of the referenced AC.
EA The final computed Effective address.
AR Generally the operand that was computed.
RES The AR register after the instruction was complete.
FLAGS The values of the FLAGS register before execution of the instruction.
IR The fetched instruction followed by the disassembled instruction.

The PDP-10 simulator allows for memory reference and memory modify breakpoints with the -r and -w options given to the break command.