Intel MDS-II Model 230 Development System

This Intel MDS-II from 1979 has a 6-slot Multibus card cage in the bottom front of the chassis, a large power supply in the middle, a CRT in the top, and an I/O controller board at the back. There is room for an 8" diskette drive to the right of the CRT, but it is only installed on the Model 220 and 225 systems.

Restoration information is here.

The back of the system has connectors for the Keyboard, Serial Ports, Paper Tape Reader & Punch, Printer, and external Floppy Diskette chassis. It also has controls for the CRT brightness and contrast.

The top board in the chassis is the IPB (Integrated Processor Board) based on a 2.6 MHz 8080 CPU and has 32 kB of RAM onboard.

The second board is a 32 kB RAM board. This board is only half populated with Intel 2118 16 k x 1 bit DRAM chips. The other 32 kB of RAM that the 8080 processor can address is on the IPB.

The next two boards make up the Intel iSBC202 Double-Density diskette controller. The board on the left is the interface to the double-density diskette drives. The board on the right is the bit-slice channel interface that executes IOPB commands and does the DMA to/from RAM.

The bottom board is an Intel iSBC310 High-Speed Mathematics Unit that does fixed and floating point math. This board is implemented with Intel bit-slice logic.

The ICE-85 that came with the system has two boards, so we will need to remove the Math board to install it. The board to the left is the ICE-85 interface board and the board to the right is the ICE-85 trace board.

The system is powered by a custom made Power One CP-214 power supply. This creates the power for the Multibus boards, CRT, IOP/IOC board, and the optional floppy diskette drive.

The IOC/PIO (Input-Output Controller) board is mounted in the back of the chassis. This board has an onboard Intel 8080A processor running at 2.448 MHz onboard, 8x Intel 2108 RAM chips providing 8 kB of RAM, and 2 to 8 kB of EPROM holding firmware. It has an onboard Intel 8271 diskette controller with the Model-220 and Model-225 systems, but not with our Model-230 system. The IOC manages the Intel 8275 CRT controller and the Intel 8041 Keyboard processor. A 2708 EPROM holds the 8 x 7 dot patterns for the CRT. There is also an Intel 8275 DMA controller and an Intel 8253 interval timer onboard.

The PIO (Parallel The Intel 8041 processor has an 8-bit parallel interface to the IPB. The 8041 has 1 kB of internal ROM and 64 Bytes of RAM. This part of the board is the interface to the paper tape reader and punch, line printer, and PROM programmer.