Intel SDK-85

Intel SDK-85

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The Intel SDK-85, introduced in 1977, was a pioneering single-board computer designed to showcase and develop for the Intel 8085 microprocessor, featuring a 6-digit LED display, a 24-key hexadecimal keyboard, and expandable RAM and ROM. Its claim to fame was making microprocessor technology accessible to engineers, students, and hobbyists, serving as both a learning platform and a prototyping tool during the early microcomputer revolution

• Manufacturer: Intel
• Type: Single-board computer
• Release Date: 1977
• Cost at release: USD $250 (CAD ~$1,400 adjusted for inflation)
• MIPS: 0.77 (770 KIPS)

Hardware Specifications

• Processor: Intel 8085A running at 3 MHz with a 1.3 μs instruction cycle
• Memory:
  • ROM: 2 KB expandable to 4 KB (using 8355 or 8755)
  • RAM: 256 bytes expandable to 512 bytes (using 8155)
• I/O:
  • 38 programmable parallel I/O lines (expandable to 76 lines)
  • Serial interface through SID/SOD pins of 8085
• Display: 6-digit 7-segment LED display
• Input: 24-key hexadecimal keyboard
• Interfaces:
  • TTL-compatible bus
  • 20 mA current loop for teletype (110 baud)

Operating System & Programming Languages 

• Operating System: The Intel SDK-85 ran a built-in monitor program stored in ROM rather than a traditional operating system. This monitor provided basic system control, program entry, memory inspection, and I/O functions directly through its hexadecimal keypad or via a teletype interface

• Supported Languages: The primary programming language for the SDK-85 was 8085 assembly language, as users wrote and entered machine code or assembly programs directly. Additionally, higher-level languages such as Intel PL/M could be used if cross-compiled on another system and then loaded onto the SDK-85

Notables

• The Intel SDK-85 was nicknamed a “system design kit” and was notable for being a complete single-board computer aimed at education, prototyping, and development for the Intel 8085 microprocessor

• It featured a rare 24-key hexadecimal keyboard and a 6-digit LED display for direct program entry-unusual for its era

• The SDK-85 could interface directly with teletypes using a 20 mA current loop, rather than the more common RS-232, reflecting its roots in early computing labs and industrial environments

• Despite only 256 bytes of RAM (expandable to 512 bytes), it was used to build games like Simon and for hardware experiments, showcasing the versatility of minimal hardware

• The SDK-85 helped launch the era of hands-on microprocessor learning and rapid prototyping, influencing generations of engineers and hobbyists

Donated by: Arlen Michaels