MK14 Firmware - SCIOS

MK14 Firmware

There are two original/official versions of the MK14 'monitor'.  The first, I have called it Version 1, was on the first release of the MK14 and is just National Semiconductors SCMPKB.  An upgrade, I have called Version 2, was produced that included the tape interface routines (previously these had to be typed in each time the machine was switched on !).  There is now also available a Version 3 of SCIOS which has had the cassette interface routines replaced with a Fast Loader developed by Ian Murray (coolsnaz2 on the vintage radio forum).


The original Mk14 manuals include listings of the firmware 'Monitor program listing' but have errors, especially Version 1.  I have repaired the listing pages from the manuals.

There is a modified version of SCIOS Version 1 that stops blanking of the 9th display digit (just one byte difference at $0046 becomes $08 'NOP' was $CA 'ST'):

I have also created source files in SB-Assembler format: (see

The Version 2 listing in the 'later version' manual has a mistake at $01FC incorrectly shown as $42 when it should be $4B, this has been corrected in the listing and binary here.

Again I have created source files in SB-Assembler format:

Version 3 is the latest version with the Fast Loader routine.

Again I have created source files in SB-Assembler format:

Pages describing the Fast Loader will follow soon.


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