# Paolo Amoroso's Journal

## A quick look at UCSD p-System on the Z80-MBC2

The Z80-MBC2 homebrew Z80 computer is a living retrocomputing museum that runs early microcomputer operating systems such as CP/M, QP/M, and UCSD p-System. Since the latter is the one I know least, I explore it with the Z80-MBC2.

On UCSD p-System the user runs programs and manages the system through a series of hierarchical menus, unlike the command interpreters of other operating systems. Navigating the menus down the hierarchy is easy, but sometimes I'm not sure how to get up one level. Pressing the Q key works most of the times, but occasionally nothing happens and I get stuck.

Running UCSD p-System gives a sense of how slow the output is on serial terminals. For example, a demo program to plot an ASCII sine wave takes almost 20 seconds over a 115200 bps serial line to the 8 MHz Z80-MBC2.

It's best demonstrated by this video, which shows the output as well as the menus:

Here the Z80-MBC2 runs in a Minicom terminal emulator session under Crostini Linux on my Chromebox.