This directory contains a disassembly of the SoftBox BIOS. The BIOS is 4K and is split into two 2716 EPROMs in the SoftBox. IC3 contains the lower half (F000-F7FF) and IC4 contains the upper half (F800-FFFF).
Several BIOS versions are available. The dates were taken from the version strings inside them.
-
1981-09-08is the September 8, 1981 version. It was found by Nils Eilers in a very early SoftBox (brown case, one LED, PCB slides in on rails, PCB is very different from all others found). -
1981-10-27is the October 27, 1981 version. It was found by Mike Naberezny in an early SoftBox (brown case, three LEDs, no rails inside). -
1983-06-09is the June 9, 1983 version. It was found by Mike Naberezny in a later SoftBox (beige case with three LEDs, like all HardBox units found). This version adds CBM 8250 support but a bug in theieeenumroutine causes it to fail for tracks 100+. It is believed that SSE produced a later BIOS to fix this bug but it has not been found. -
biosis not an original BIOS from SSE. It is a present-day version based on1983-06-09that fixes CBM 8250 support.
The .bin files are dumps of original EPROMs from Small Systems
Engineering Ltd. The corresponding .asm files are disassemblies that
should assemble to identical binaries.
Disassemble using z80dasm:
$ z80dasm --labels --origin=61440 1981-10-27.bin > 1981-10-27.asm
Assemble using z80asm:
$ z80asm --input 1983-06-09.asm --output 1983-06-09.bin