Heathkit H-11 Computer

Introduced in 1977 at $1295 in kit form. The H11 originally sold for $1295 in kit form. It was available from Heath Company until Spring/Summer 1982 (last catalog to offer the system).

Info from 1977 catalog

The Heathkit H11 Computer

Two of the finest names in electronics, Heath Company and Digital Equipment Corporation (DEC) combine to bring you the world's first 16-bit computer priced within reach of the general public!


Heathkit/Digital Equipment Corp H11 Digital Computer

  • Uses the performance-proven LSI-11 CPU
  • Executes the famous 400+ PDP-11/40 Instruction Set and powerful software
  • Fully wired and tested DEC KD11F board
  • 4096 x 16 read/write MOS semiconductor memory
  • Mechanically superior bus with 38 high-speed lines
  • Single-level, vectored automatic priority interrupt
  • Efficient switching power supply with built-in cooling fan
  • Backplane guide assembly for microprocessor and up to six I/O and memory modules

The new Heath/DEC H11 personal computer combines the advanced performance-proven hardware and software of the famous LSI-11 with Heath's expertise in kit design and documentation to bring you a personal computer of almost incredible power and performance. Equivalent commercial versions of the H11 would cost literally $1000's of dollars more!

The LSI-11 bus has 38 high-speed lines containing data, address, control and synchronization lines. Sixteen lines are used for time multiplexing of data and addresses. All data and control lines are bidirectional, asynchronous, open-collector lines providing a maximum parallel data transfer rate of 833K words per second under direct memory access operation.

The fully wired and tested KD11F board contains the CPU with eight general registers which serve as accumulators, index, autoincrement/autodecrement registers or stack pointer; and a 4096x16 MOS semiconductor memory. Additional cards can be added to expand memory up to 20K in the H11 cabinet (32K words total).

The backplane/card guide assembly holds the microcomputer and up to six I/O and memory modules. All LSI-11 bus data control and power connections are routed on the printed circuit backplane to each module location. The backplane/card guides are fully compatible with all standard DEC LSI-11 accessories.

An efficient, well designed power supply provides the required DC voltage for the LSI-11 as well as all accessory modules. The supply features overvoltage and overcurrent/short circuit protection, power fail/automatic restart and a built-in fan for quiet cooling The dual primary power configuration can be connected for 115 V, 60 Hz or 230 V, 50 Hz AC.

Other features of the H11 include single-level, vectored, automatic priority interrupt, real-time clock input, ODT/ASCII console routine/bootstrap resident in microcode. The H11 is supplied with versatile PDP-11 software (described below) which uses the famous PDP 11/40 instruction set with over 400 commands.

The H11 is housed in a rugged metal cabinet with structured foam side panels, 6-1/2" H x 19" W x 17" D. For 110/220 VAC, 50/60 Hz.

Kit H11, shipping weight 43 pounds. ............... 1295.00

PDP-11 software included with the H11 consists of: ED-11 editor; PAL-11S relocatable assembler; LINK-11S link editor; Absolute Loader; ODT-11X debug program; IOX executive program; DUMP AB and DUMP R; BASIC (with strings) and FOCAL (4K and 8K versions). The software requires a minimum of 8K memory with 12 to 16K total recommended for maximum capability. See software License agreement, next page.

H11 Accessories, Software and Manual Set

Fully Wired and Tested KD11F Circuit Board. The "heart" of the LSI-11 is the standard DEC LSI-11 microcomputer board. The 16-bit CPU functions are contained in 4 silicon gate N-channel MOS LSI integrated circuit chips for high reliability and superior performance. The 4096-by 16 read/write MOS semiconductor memory is composed of LSI 4K dynamic RAM chips for fast access time with low power consumption. The board is fully wired and test to facilitate kit assembly and provide greater reliability and less chance of error.

The compact, efficient power supply uses less power to operate and generates less heat than conventional supplies. Has overvoltage and overcurrent/short-circuit protection, plus automatic power-up and power-down sequencing for high reliability and long life operation. A built-in quiet-running fan provides efficient cooling and prevents heat buildup.

Rugged steel chassis and extra-thick backplane with heavy, solid connectors for added strength.

Card cage swings up for easy access and service even when the H11 is operating.

Accessory boards slid directly into card guide and are held securely in place. All card connectors are supplied for easy expansion.

H11-1 4K Memory Expansion Module. Plugs directly into H11 backplane, adds 4K x 16-bit word capacity to H11 memory. Access time, less than 500 nS. Fully compatible with PDP 11/03 and other LSI-11 backplane machines

Kit H11-1, Shipping weight 2 pounds. .............. 275.00

H11-2 Parallel Interface. Required for interfacing the H11 to the H10 Paper Tape Reader/Punch. Also for other LSI-11 backplanes. With connectors.

Kit H11-2, Shipping weight 2 pounds. .............. 95.00

H-11-5 Serial Interface. For use between LSI-11 bus and serial devices such as the H9 video terminal or LA36 DEC Writer II. Includes all mating connectors. For H11, other LSI-11 backplane machines.

Kit H11-5, Shipping weight 2 pounds. .............. 95.00

H11-6 Extended Arithmetic Chip. Adds powerful arithmetic instructions to the LSI-11, including fixed point multiply, divide and extended shifts plus full floating point add, subtract, multiply and divide. Helps minimize or eliminate arithmetic subroutines, speeds up program execution and eases program development. Saves memory space too. 40-pin dual inline package IC plugs into socket on KD11F board.

H11-6, Shipping weight 1 pounds. ................. 159.00

H11 Manual Set only $25

Price of manual set is refunded when you purchase an H11, simply enclose HM-1100 sales slip with your order.

Complete assembly and operations manual for H11, H11-1, H11-2, H11-5, H9 and H10. Also includes complete software documentation.

HM-1100 Manual Set. Shipping weight 12 pounds. ..... 25.00

Note: Manuals are included with each kit.

HEATH/DEC Software License Agreement:

This form MUST accompany your H11 computer order.


HEATH COMPANY (hereinafter referred to as HEATH) pursuant to a license agreement with Digital Equipment Corporation (hereinafter referred to as DIGITAL) does herby grant to CUSTOMER a non-transferable and non-exclusive sublicense to use the Binary Software Program(s) PTSP-11 Paper Tape System, FOCAL/PTS Language Processor, BASIC/PTS Language Processor (hereinafter singularly and/or collectively referred to as "Software") on the following terms and conditions.

Software is furnished to CUSTOMER for use on a single CPU only and may be modified, or copied (with the inclusion of DIGITAL'S copyright notice) only for use on such CPU. The CUSTOMER shall not provide or otherwise make available the Software or any portion thereof in any form to any third party without the prior approval of DIGITAL. Title to the ownership of the Software shall at all times remain with DIGITAL.

Info from the Winter 1980 Heathkit Catalog

Heathkit H11A Computer brings 16-bit power to the advanced computerite - at an affordable price

The most popular business/science computer on the market is now available at a price you can afford

Designed for the more serious computerite, the Heathkit H11A Computer offers the power and potential you need to implement more sophisticated computing applications. Most computerites find that their problem-solving and programming capabilities grow quickly, and before long, they run out of computing power. The H11A is the computer that meets the demand for superior performance is scientific, educational and small business applications. When you buy the H11A Computer, you get computing potential.

The H11A give you all the power, speed and flexibility you'll ever need in a microcomputer. It uses the same powerful microprocessor and runs all software designed for the DEC PDP-11/03. You can choose from a vast selection of practical programs to run you home more efficiently, to reduce the clerical costs of your business and to process all types of data more efficiently than before. If you've been around computers and your computing needs require extra power, the H11A Computer is designed for you.

The 16-bit vs. 8-bit issue: Your choice of a 16-bit or 8-bit computer depends upon your needs. If you're an advanced hobbyist or professional with demanding computer application, the 16-bit H11 is your best choice. The H11A has adequate computing power, even for the more complex and sophisticated jobs that you will be tackling later. When you buy the H11A, you are purchasing ultimate immediate performance and maximum future potential.

The H11A features the new, physically smaller KD11-HA microcomputer (half-size LSI-11/2). This makes the Heathkit H11A identical to the DEC PDP-11/03, but at a fraction of the cost. This smaller configuration allows you to put more computing power and versatility into the H11A by providing an extra plug-in slot for additional memory or I/O interface.

You get the flexibility to configure the exact computer system you require with the H11A. Seven plug-in slots let you add any combination of I/Os and a maximum of 60K bytes memory. The basic H11A Computer is supplied with a handsome cabinet, heavy-duty power supply, and a backplane that includes bus and a fully assembled CPU board. You can add your selection of optional memory and I/O accessories to the mainframe. Awide selection of software is also available. (See pages 82 and 83 for accessories and software to make your H11A Computer System even more versatile. Complete H11A Systems Software for the H27 Floppy Disk System is available below).

Get the power and versatility you need in the H11A Computer

  • 16-bit computing power with up to 60K words of memory
  • DEC half-size KD11-HA (LSI-11/2) CPU
  • Compatible with DEC PDP-11/03
  • Plug-in flexibility for memory and I/Os

 Learn by building it yourself. What better way is there to know your computer than by building it yourself? The Heathkit H11A Computer lets you understand it better. You can build it yourself and benefit from the knowledge - and the savings. Like all Heathkit designs, the H11A comes with an easy-to-follow assembly manual - and a nationwide network of service centers to help you, should a problem arise. And when you build it yourself, you can also perform more of the service steps yourself, to keep your computer in top operating form.

Whether you buy an H11A Computer System or the computer itself, compare the price of the H11A with comparable 16-bit computers. Buy this extra-powerful Heathkit computer and find out why the combination of advanced design and quality components make the Heathkit H11A one of the best 16-bit computer values anywhere. 

Kit H11A, Shipping weight 43 pounds.................. 1195.00

Factory Assembled and Tested H11A Computer.

WH11A, Shipping weight 43 pounds....................  1895.00

Heart of the H11A - the KD11-HA Microcomputer

The KD11-HA 16-bit Microcomputer module forms the heart of the H11A Computer. It's only half the size of the KD-11F (LSI-11), but you get more flexibility when you configure your H11A System.

There is no on-board memory, so you can match your RAM/ROM requirements to meet your particular needs. And full compatibility with the LSI-11 family means you can combine components form both the LSI-11 and LSI-11/2 families.

Features of the KD11-HA include a PDP-11/34 instruction set, a raw computer speed of 380 nS microcycle time, resident firmware debugging (ODt) and ASCII console routines, as well as single and double operand instructions. The KD11-HA gives you the power and flexibility you need for advanced system configurations.

H27 Floppy Disk gives you instant access to data

  • Z80 Microprocessor-based controller
  • Full compatibility with DEC RX01 (PDP-11/03)
  • Fast head step time of 8 mS
  • Dual-drive capability for a total capacity of 1/2 Meg bytes

The H27 gives you dual-drive versatility, with a total of 1/2 Meg bytes of program and data storage to give you enough room for most of your general-purpose application needs. The Z80 Micro-controller in the H27 provides an average access time of 252 mS. You'll have virtually immediate access to all your files and programs.

You get full compatibility with DEC RXV11 (PDP-11/03) hardware and software, to give you the capability of using the hundreds of applications programs written by users of the DEC PDP-11/03, the world's most popular microcomputer. Performance-proven hardware and software base provides outstanding computer power. While compatible with the RX01 system, the H27 gives you more. A built-in self-test diagnostic on power-up protects existing programs on you disks. A mechanical interlock prevents accidental media damage (if the floppy is not seated properly, the door will not close and the H27 will not operate). A write-protect function protects important files and programs from being written over inadvertently. And a reformatting procedure gives you the capability of writing in the IBM 3740 standard format.

A single-board interface/bootstrap uses one backplane slot, leaving more space for memory and I/O additions to your H11A Computer System. The H27 Floppy Disk System measures 8" H x 18" W x 20" D. It operates on 120 or 240 VAC, 60 Hz power. To use the full capabilities of the HT-11 Operating Systems Software, designed for use with the H27 Floppy Disk System, you need at least 16K words of memory.

Kit H27, Shipping weight 93 pounds. Motor Freight ..........................................  1945.00

WH27 Dual-Drive Floppy disk System. Fully assembled and tested.

WH27, Shipping weight 69 pounds. Motor Freight ............................................  2595.00

H27-2, Pkg of 5 Blank Disk. IBM 3740 format. Shipping weight 2 pounds. ............ 30.00

H11A Operating System Software for the H27 Floppy Disk System to help you get your computer system operating quickly and efficiently

The HT-11 Systems Software lets you immediately enjoy the full benefits of a rapid-access floppy disk system. You get easy-to-use programs, including:

EDIT: A text editor to create or modify files for programs and documentation.

EXPAND, ASMBLE AND CREF: Utility programs for macro-expansion, Assembly Language processing and cross-reference listings. Supports the entire PDP-11 instruction set and several pseudo-operators.

LINKER: Converts object modules produced by the assembler or the FORTRAN compiler into a run time format. Services include relocation of code, linking of global references and the creation of a runable program file for use by the rest of the system.

LIBRARIAN: Creates and maintains libraries of subroutines for use by the linker.

PIP: The Peripheral Interchange Program is the file maintenance and transfer utility program of the HT-11. It has commands for moving, copying and renaming files, plus other commonly-used file operations.

ODT: The HT-11 On-line Debugging Technique aids in debugging user programs by providing commands to display and alter the state of a running program.

BASIC INTERPRETER: This high-level conversational programming language offers access to the HT-11 I/O system and file structure through the BASIC Language. Extensions to standard BASIC include variable -length strings, sequential files, virtual memory arrays, chaining and overlay capability. A "desk calculator" mode can perform once-only calculations or serve as an aid in debugging.

MISCELLANEOUS PROGRAMS: Dump prints contents of files in any of several useful formats. SRCOM compares two files, prints summary of differences.

The easy-to-use HT-11 Operating System for the H27 Floppy Disk System extends the H11/H11A's capabilities. Minimum requirements include an H11 or H11A Computer with at least 16K words of main memory, a console terminal and interface, and a Heathkit floppy disk drive, controller and interface

*HT-11 Operating System with BASIC, Shipping weight 12 pounds .................... 350.00

FORTRAN for HT-11 System. Binary software features complete ANSI standard 1966 FORTRAN IV with extensions for increased speed. Some of the extensions include relaxation of statement ordering, use of expressions nearly anywhere, direct access I/O, TYPE ACCEPT and PRINT I/O statements, END and ERR parameters, random number generator, IMPLICIT statement, more.

*HT-11-1, Shipping weight 9 pounds. ......................................................................... 250.00

*Note : The HT11 Disk Operating System and HT-11-1 FORTRAN are compatible only with the Heath H27 or WH27 Floppy Disk Systems. To obtain this software, the Customer Software Sublicense Grant must be signed and you must include the make model and serial number of your CPU in the blank provided on page 82 and include the Grant with your order.



Last Modified: Sunday, 25-Feb-2024 22:37:36 PST

Contact Details

Mark Garlanger

Email: heathkit [at] garlanger [dot] com

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Website: www.garlanger.com



This site is dedicated to preserving the history of the original Heathkit computers. They were initially release in 1977 and included the 8-bit H-8 and 16-bit H-11 systems. The H89 was released in 1979.