The Nascom 2 belongs to a generation of microcomputers in which hardware and software could still be experienced directly. Instead of booting into a graphical interface, the system starts in the NAS-SYS monitor. From there, you can display and edit memory, load programs or execute code directly at a given address.
Some may wonder why the Nascom 2 was chosen rather than the Nascom 1. Was the Nascom 1 not the forefather of the home computer, intended at the time to compete even with the American garage computer, the Apple I?
In terms of performance, the Nascom 1 was not very different from the Nascom 2, but the second version resolved many of its early shortcomings. The Nascom bus was now located directly on the main board, eliminating the need for a separate buffer board. Timing became more reliable, and the main board provided more memory sockets. NAS-SYS 3 was now supplied as standard as well. Before that, the NASBUG monitor ROM had left a great deal to be desired.
A computer made to be understood
The Nascom 2 separates its tasks clearly: the Z80 executes programs, a dedicated part of RAM serves as screen memory, and ROMs provide the monitor, BASIC and additional tools. This transparent structure still makes the system interesting for education, repair, software archaeology and personal experiments.
Typical tasks are performed directly from the monitor:
- display memory starting at an address
- change individual bytes
- load programs in NAS or CAS format
- execute machine code at an address
- start Microsoft BASIC and return to the monitor
NAS-SYS as the starting point
NAS-SYS is a command line, debugger and operating-system kernel in one. Its concise command language provides direct access to the machine. Anyone starting with the Nascom 2 today learns not only about a historic computer, but also about fundamental concepts such as addresses, registers, memory images and I/O ports.
This website will gradually expand its historical coverage with schematics, original documents and verified sources. Technical information about the FPGA implementation is kept clearly separate.
From the original to FPGA
The MEGA65 implementation preserves the machine's direct character while adding practical features: programs are loaded from an SD card, disk drives are provided as DSK images, and a hardware monitor exposes the state of the Z80. This preserves the original operating model without giving up modern storage media.