Architecture The 380Z was packaged in a large, black,
19-inch rack-mount, rectangular metal case containing the power supply, a number of
printed circuit boards and the optional 5¼-inch
floppy disk drives. The front panel had a pair of strong carrying handles, a keyswitch and a reset button. The keyswitch controlled power and also enabled the reset button. The
keyboard was separate and came in a tough metal case. Early versions were contained in a light blue metal case with a white front and had only a cassette interface or 8-inch
floppy drives; only a small number of these were made. An optional 8-bit
ASCII paper tape punch/reader was also used, as this was a common storage medium at the time - where previous use of a computer had been limited to a
teletype machine connected to
mainframe by telephone. The system used a passive
bus architecture with no motherboard – all electronics were contained on a number of cards interconnected by
ribbon cable. The only
microprocessor offered was a 4
MHz Z80A. Typical configurations were 16 KB for cassette-based systems and 32, 48 or 64 KB of memory on disk-based systems. Main memory was not used by the text or graphics video cards, although memory on the video cards was
bank switched into a dedicated 1.5 KB address block. Both card types were fitted with their own dedicated video memory. In addition to the text-mode video card the system could be enhanced with a
high-resolution graphics (HRG) board. The board was fitted with a dedicated bank of 16 KB of video memory and supported two graphics modes: • High resolution: 320×192
pixels, 2
bits per pixel (4 colours), 1
page. • Medium resolution: 160×96 pixels, 4 bits per pixel (16 colours), 2 pages. A programmable
lookup table with an
8-bit output mapped the pixel value to one of 256 different colours (analogue
RGB output) or intensities (composite video). In RGB mode, each palette index can configured by specifying the amount of each primary colour. Possible ranges are 0 to 7 for Red and Green, and 0 to 3 for Blue (ex: 000 generates black; 773 generates white). This arrangement is known as
8-bit color and also used on other machines like the
MSX2 or
Atari Falcon. Output from the graphics board was mixed with output from the text-only video card, allowing text and graphics to be easily overlaid. The graphics output only covered the top 20 lines of the text display and therefore text output could be set to use only the bottom 4 lines if overlap was not desired.
Storage Mass storage was either via
cassette tape or
floppy disk (which required a
disk controller card). The cassette interface operated at either 300 bit/s (
CUTS standard) or 1200 bit/s. COS 4.0 and later systems were not fitted with the cassette interface. Early systems could be fitted with an optional
single density floppy disk controller card that could interfaced to either internal 5¼-inch or external 8-inch floppy disk drives. Disk capacity was 80 KB per side on 5¼-inch disks and 250.25 KB per side on 8-inch disks. Double-sided disk drives were treated as two independent disks with a
drive letter per side. CP/M used the first 4 tracks on 5¼-inch disks and the first 3 tracks on 8-inch disks, reducing the usable capacity of a single density, single-sided 5¼-inch disk to 72 KB. Support for a "Winchester"
hard disk drive could be provided using an intelligent Host Interface Board (HIB) that implemented a
SASI interface. Hard disk systems were mainly used as
file servers for networked
LINK 480Z systems.
Interface cards The passive bus allowed a number of cards to be installed in the 380Z. All systems required: • CPU/RAM – holding the Z80A
CPU, firmware ROMs, and up to 32 KB of RAM. The card also provided a parallel
Centronics printer port (not always connected). • Video, either a VDU-40 or VDU-80 card – providing the 40×24 or the switchable 80×24/40×24 character text displays, respectively. Other cards were optional, and included: • RAM – a second CPU/RAM board, with processor and ROMs omitted, holding up to a further 32 KB of RAM. • Floppy Disc Controller (FDC) – a single density disk controller, which also provided an
RS-232 serial interface (SIO-4). • Intelligent Disc Controller (IDC) – a double density disk controller with its own dedicated microprocessor. • High Resolution Graphics (HRG) – up to 320×192 pixels. • Host Interface Board (HIB) – for hard disk support. • 380Z Network Interface Board (380Z-NET) – a proprietary 800 kbit/s network interface used to interconnect to a network of LINK 480Zs. • Serial Interface-1 (SIO-1) – available as the SIO-1A (RS-232) or SIO-1B (20 mA
current loop). • Serial Interface-2 (SIO-2) – available as the SIO-2 (RS-232) or SIO-2B/SIO-3 (20 mA current loop). • Serial Interface-4C (SIO-4C) – providing an SIO-4 interface on cassette systems without the FDC card. •
IEEE-488 Interface. • PIO Interface Development Board – providing three Z80 PIOs and a Z80 CTC. • Analogue I/O Board – providing 16 input channels and 2 output channels. == Firmware ==