Beginning with the release of the 4004 microprocessor in 1971, after releasing a new processor, Intel would make a System Development Kit for that processor. The SDK boards had the bare minimum of support hardware necessary to run the processor, and were intended for use designing systems around it. The SDK-85, released in 1978, is for the 8085A microprocessor.
The 8085A is 100% backwards software compatible with the 8080A, but adds two instructions for the additional serial I/O hardware in the 8085A. The 8085A only needs a single +5V power supply, so implementing hardware is simpler than with the 8080A.
It provides 2k of ROM, 256 bytes of RAM, an I/O chip that provides 38 I/O lines, and a keyboard controller, as well as a 24-key keyboard and 6-digit 7-segment LED display. This is sufficient hardware for the user to enter a program using the keyboard and read it out using the single-row display. In addition, a large area of prototyping board is on the left side of the board for the user to install additional hardware. Current-loop serial I/O is supported using the SID/SOD ports on the 8085A, allowing input and readout through a Teletype terminal rather than the onboard keyboard and display.