2. System Components

The SCPC88 board set consists of four single-height Eurocards. These contain the main functional blocks of the PC.

2.1. The SCPC88 Processor Board

This is the heart of the system, containing the 8088 CPU (running at 4.77 or 7.16 MHz, software-selectable, a socket for the 8087 maths coprocessor (8087-2 not included as standard), BIOS EPROM, user EPROM socket, 256k dynamic RAM, FE2010A LSI IC, and the STEbus interface. The FE2010A replaces several LSI chips from the PC, and is totally compatible with those devices.

2.2. The Disk Controller Board

The SPDC uses the FE2100 chip, STEbus buffers, and either the Intel 8272 or the NEC µA765 Floppy Disk Controller chip. Programming details can be found in the data booklets for either of the two controller chips (as they are software identical, and the FE2100 consists of a single register which is described in the board manual.

2.3. The Communications Port Board

The SPCOM uses the Paradise PPC1 chip to provide the Centronics-style parallel printer interface port. The two serial communication ports are driven by two 8250A chips. The two channels of serial output are via an Arcom standard 10-way bergstick connector (which can be taken to two 25-way D-type RS232 connectors) and a 20-way bergstick connector (which can be taken to two cable-mounting PC-compatible 9-way D-type connectors. The parallel printer port 26-way bergstick connector can be taken via ribbon cable to a cable-mounted PC-compatible 25-way D-type IDC connector.

2.4. The SPEGA Enhanced Graphics Adapter

The SPEGA board is based around the Paradise PEGA1A, a single 84-pin video interface chip. The 256k of memory stores a display of up to 720 × 350 pixels, in up to 16 logical colours from a palette of 64 physical colours. Note that the pixels’ colour data are output as six TTL digital signals. To get the maximum performance out of the SPEGA, a PC-compatible colour monitor is needed, although other monitors can be driven.

Analogue RGB colour monitors will need these signals fed through a resistor network (effectively three 2-bit DACs) to drive the three colour inputs. The SPEGA is 100% software compatible with the following boards:

EGA (Enhanced Graphics Adapter)

CGA (Colour Graphics Adapter)

MDA (Monochrome Display Adapter)