Jupiter Ace - System Characteristics

System Characteristics

The Jupiter ACE is often compared with ZX81 due to its similar size, low cost, and similar form factor, although internally it is an independent design. The ZX81 used 75% of its Z80 CPU time to drive the video. In ACE the Z80 CPU was fully used for running programs. The ACE used dedicated video memory of 2 KB, leaving the 1 KB main memory free for user programming.

The Jupiter ACE was new to the market and the designers couldn't afford to use an uncommitted logic array (ULA), a design approach then gaining popularity in other computers (such as the ZX 81) to reduce component count, because these weren't economical in small quantities. Instead they reduced the number of chips required via clever design.

Like the Spectrum, the Ace used black rubber keys. Audio capabilities were CPU controlled with programmable frequency and duration. Sound output was through a small built-in speaker. A television was needed as a display - which was in black and white only.

ACE's FORTH was "ten times faster than Basic" (a reference to ACE FORTH), and used less than half the memory (which was a costly luxury at the time) of an equivalent program written in interpreted BASIC. Forth programs tend to be more memory efficient than the bigger programs; as they become bigger, they reuse more previously-defined code.

Control structures could be nested to any level, limited only by available memory. It also allowed recursive programming, if desired. Programs and data storage was by means of a common cassette tape, which was typical of home computers of the time.