The Z88 evolved from Sir Clive Sinclair's Pandora portable computer project which had been under development at Sinclair Research during the mid-1980s. Following the sale of Sinclair Research to Amstrad, Sinclair released the Z88 through his Cambridge Computer mail-order company, as he was no longer permitted to use the Sinclair name after the sale. The machine was launched at the Which Computer? Show on 17 February 1987.[6] Early models were contract-manufactured by Thorn EMI but production later switched to SCI Systems in Irvine, Scotland.[7]
Design
The Z88 is a notebook computer weighing 0.9kg (2.0lb), based on a low-power CMOS version of the popular Zilog Z80microprocessor. It comes with 32kB of internal pseudo-static RAM and 128kB of ROM containing the operating system (called OZ). The memory can be expanded up to 3.5MB of RAM, the contents of which are preserved across sessions. An integrated capacitor prevents the Z88 from losing its data for the limited time it takes to change the batteries.
The machine uses a membrane keyboard, which is almost silent in use; an optional electronic "click" can be turned on to indicate keystrokes. The Z88 is powered by four AA batteries, giving up to 20 hours of use. It has three memory card slots, which accommodate proprietary RAM, EPROM or flash cards, the third slot being equipped with a built-in EPROM programmer. Card capacities range from 32kB to 1MB.
The 64kB addressable by the Z80 processor are divided in four banks of 16kB each. The maximum memory of 4MiB for the system is also divided in 256 segments of 16kB each. The hardware can map any of the 16kB blocks to any of the four banks. The first 512kB are reserved for ROM; the next 512kB are reserved for internal RAM. The next 3MB are assigned to each one of the three memory slots.
Since 1998, a 1MiBFlash memory card is available which provides convenient non-volatile storage. Once written to the card, files are safe and not reliant on a power supply. Unlike traditional EPROM cards (erased with an external ultraviolet light), this one can be electrically erased in the computer's slot. The first generation of card only worked in slot 3 where a 12V signal (Vpp) is available. The later generation is based on AMD chips and runs with 5V for erasure. It is possible to read, write and erase flash cards in the three slots and the internal one.
It is also possible for an experienced user to replace the built-in 32kB RAM chip with a bigger 128 or 512kB static RAM chip. However, the latter requires some extra board modifications, and 512kB is the biggest size that can be addressed by the Z88 for the internal RAM. A similar modification is possible for the internal ROM slot. A 512kB flash chip can replace the original ROM, allowing an upgrade of the operating system.