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Plus2 was the second chapter on MICROCode Consulting monitor ROM and BIOS upgrades.  A complete replacement for the Xerox 820-II or Xerox 820-I/BigBoard sporting the Emerald Microware disk drive extender plug-in, Plus2 offered enormous improvements over the OEM monitor and BIOS.  Using a similar design as its parent, SmartROM, Plus2  supported multiple drive formats and even a hard disk.

Written in Z-80 assembler for use under QP/M, CP/M 2.x and compatibles, features of Plus2 include:


Package Version Date Size (bytes) Download time
(28.8K baud)
Click to
2.5MHz Xerox keyboard ROMs 0.2a Mar 1986 3802 2sec p2x25.zip
4.0MHz Xerox keyboard ROMs 0.2a Mar 1986 3802 2sec p2x40.zip
2.5MHz generic keyboard ROMs 0.2a Mar 1986 3802 2sec p2g25.zip
4.0MHz generic keyboard ROMs 0.2a Mar 1986 3802 2sec p2g40.zip
Plus2 software 0.2 Mar 1986 71k 26sec plus2.lbr
Plus2 documentation (updated) 0.2 Nov 2004 340k 2min 5sec plus2.pdf
Plus2 software and documentation 0.2 Nov 2004 318k 1min 56sec plus2.zip


Installation of this package entails the following steps:

  1. Burn the "A" and "B" ROM images onto two 2716 EPROMs and then replace the "A" and "B" ROM chips prominently located in two adjacent sockets on the motherboard.  Upon power-up, you should immediately see a sign-on message.  If you accidentally reverse the order and plug the EPROMs into the wrong ROM socket, nothing will work but your computer will not be damaged.  (Conversely, plugging in the EPROMs upside down could damage your motherboard.)
  2. Installation of the software package entails running NULU on your CP/M or QP/M system and extracting the files to your system to some drive/user area, likely drive A, user 0 as this is operating system software including a new operating system BIOS.
  3. Although not required, follow the directions given with your QP/M or CP/M operating system for replacing the BIOS in the operating system boot image.  You may be unable to use some of the features offered by this package such as date/time stamping and multiple drive support if you do not replace your BIOS.

This is restricted for personal use software that is provided without any warranty whatsoever as described in the legacy Z-80 home page.