Intel MDS-II Model 230 Development System

This Intel Intellec MDS-II (Microcomputer Development System) Model 230 from February 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. An external dual 8" diskette chassis is included. This chassis weighs 73 pounds.

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. There is a switch that selects the CRT mode from Diagnostic, Line, and Local. When in Diagnostic mode the on board 8080 CPU tests the keyboard and CRT. The Diagnostics can test the internal floppy diskette diskette drive, but our model 230 does not have one. It also has controls for the CRT brightness and contrast.

The model 230 of the MDS-II came with an external dial diskette chassis and an Intel 202 double-density diskette controller. The February 1979 matches the date on the MDS-II.

The top board in the chassis is the IPB (Integrated Processor Board) based on a 2.6 MHz 8080A-2 CPU and has 32 kB of RAM onboard. There are two 2716 2 kB EPROMs on this board. One contains the 8080 monitor, and the other contains the boot/diagnostic code.

There are two serial ports implemented, one for RS-232 and one for 20mA current loop.

Notice that the Intel B3222 DRAM Refresh Controller near the right ejector handle has the corner broken off the top layer of the ceramic. The chip seems to work OK anyway.

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 diskettes have a capacity of 1 MB, but unfortunately have an unusual format that cannot be read by any other diskette controller.

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. We will need to remove this board to install the ICE-85 boards.

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. This power supply can supply +5V@30A, +12V@2.5A, -12V@0.3A, -10V@1A, +15V@1.5A, and +24V@1.7A.

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.

The jumpers in the image configure the serial ports on the IOC.

W1: A-B, C-D RTS & CTS not swapped

W2: A-B, DSR connected

W3: Open, External Clock isolated

W4: Open, RS-232 DTR isolated from Data Terminal Ready

W5: A-C, RS-232 RTS & CTS looped

W6: A-D, B-C, RS-232 RxD & TxD swapped

W7: A-B, C-D, CH #1 RxD & TxD not swapped

The MDS-II also came with an Lear Siegler, Inc, 200 Series Ballistic printer. We have the manual for this printer. We didn't find any information on this printer other than a few mentions in advertising. We will scan the manual and send it to Bitsavers.

From the connectors on the back, the printer has RS-232 serial, Parallel, and Current-Loop interfaces. Based on the Parallel port connector, it is probably a Centronics style interface.

The advertisement to the right came from the November 1977, Volume 23 Number 11, issue of Datamation.