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Release Date:
Machine:PAL & NTSC
Code Type:Machine code
Coded by:S., Christian (Solder)
Additional Coded by:H., Jim (BushRat)
Notes:AKA OS 92. Download contains both NTSC and PAL replacement Kernals, plus a replacement BASIC rom. See installation instructions in "Description" below.
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OS92 Screenshot

Derived Software

Appeared On Compilations
Club Info 28

Operating System 1992.3 (OS92.3)

Documentation upgrade 10/10/96

by James Hehl

This set of EPROMs are intended as a replacement for your present BASIC and KERNAL ROMs. They are to be inserted in the internal ROM slots U23 (BASIC) and U24 (KERNAL).

My current Plus/4 setup uses this operating system and the V4 Super Utility ROMs in the place of the internal ROM software... it's great!!


The first thing that you will notice is that the screen is in lower case "Business mode". This is normal and will allow reading certain directories, like GEOS, a lot easier. The screen will now say:

Commodore Basic V3.5 60671 Bytes free


The F-Keys are reprogrammed and the new definitions can be checked by using the KEY command. If you have nothing in the internal ROM sockets, then the F1 key will be programmed with the SCRATCH command (scR). The other F-keys are defined as the following:



When you use either the DIRECTORY command or the F3-key, you will notice that all of the filenames are followed with a colon (:). This is a new feature and will make life, with your Plus/4, a LOT easier. Any time that you use the DIRECTORY command, just press the Stop key to end the directory scrolling at any point that you want. Then you may cursor to the filename that you want to work with (on the visible directory listing). Pressing F2 will DLOAD the file. Pressing the F4 key (shifted F1) will DLOAD and RUN the file. If you have no internal ROMs (the F1 key being defined as SCRATCH) then you will be able to select and SCRATCH files, right from the directory.

Cursoring to a filename and using the Logo(C=)/RunStop key combination will not LOAD and RUN the file, sorry! Using the F4 key is the proper way of doing this.

If you'd prefer eliminating the colons after the filenames, use the following POKEs to toggle them:

POKE 245,1 to turn off colons
POKE 245,0 to turn on colons

These POKEs will remain in effect until the machine is turned off, cold reset or the reset button on the side is pressed.


When using the DIRECTORY or LIST commands, you can stop the screen scrolling with the Spacebar. Pressing it will stop the scroll. Pressing any other key will continue the scroll. This makes viewing a directory or program listing a lot easier. This action is also useful within the MONITOR when using the D (Disassemble) and M (Memory) commands.


Several obsolete commands have been replaced with some new functions:

OLD replaces LET
BANK replaces BACKUP
LA replaces GO

The OLD command will allow you to UN-NEW a program. Try it out by LOADing a short program. LIST it. Then type NEW. LIST it again and it will be gone. Finally, type OLD then LIST the program... you'll see that it is back.


The BANK command is used to change the current BANK number, that you are working in, if you are using a 256K expanded Plus/4. It is NOT active if you are using a standard 64K machine. There are four 64K banks in the expanded machine (banks 0-3). The default bank is 3. The memory below $1000 isn't switched by the BANK command. If you add 128 to the bank number, then the memory area below $4000 will not be switched.


The AUTO command had been improved, to properly position the cursor one blank space beyond the next line number.


The LA (Load Absolutely) command will give you the quick equivalent of a BLOAD (LOAD"filename",8,1) function. The syntax is:



You may do a COLD RESET, from the keyboard, by pressing the Shift, Control and C keys at the same time.


You may do a WARM RESET (retaining the BASIC program in memory) by pressing the Shift, Control and W keys at the same time.


This chip set is completely compatible with every Plus/4 program that I've tried it with. There are a couple of things that you should watch out for... if you are using a program, that you've not had any trouble with, and suddenly find that it stops with a ?SYNTAX ERROR. If this happens, type HELP or LIST the offending line. You may find that one of the old keywords (LET, BACKUP or GO) is in there. Here's an example:

230 NEXT I:GO TO 1000

will now say:

230 NEXT I:LA TO 1000

The GO in the original is now recognized as the new keyword LA. The program cannot execute it and stops with a ?SYNTAX ERROR. There is really nothing wrong with the line, except in this case, it was an example of sloppy programming (HEY, we were probably ALL guilty of this at one time...) that caused the problem. The programmer never intended a GO in this line. He actually intended it to be a GOTO. He should have gone ahead and used:

230 NEXT I:GOTO 1000

then there would have been no problem. He simply left a space between the GO and the TO in the line. BASIC is normally happy to accept the command and eliminate the extra space (since it recognizes the TO as part of a legitimate command) when it executes the line. This extra spacing used to be a common practice for making listings a bit more readable. All you would need to do, to correct this problem, is to delete the extra space between the GO and the TO.

As far as the LET and BACKUP commands are concerned, I haven't seen them used for a MANY years. Just be aware that some VERY OLD programs, just might have them in there!

If you are going to compile programs, using Austrospeed+4 or NorthSpeed, you will need to change a couple of commands. The compiler will work properly if you substitute the following:

1. Use LOAD"filename",8,1 instead of using LA"filename"
2. Use POKE64790,x (where x equals the bank number) instead of BANK,x.

If you are using the FSD+4 (1551), the Kernal Reset will now properly initialize this drive, whether you are using 50 or 60HZ interrupt timing.

The MONITOR command L (LOAD) will automatically default to the disk drive, instead of the Datassette. Also, while in MONITOR, you may find the beginning address of a program in locations $9b and $9c, in low/high format. You will find the end address of the program in $9d and $9e, in low/high format.

This chip set corrects the errors in the RS232 routines in the Plus/4. It will properly handle the XON/XOFF protocals properly for high speed communication.

Install in place of the original ROMS:
OS92 BASIC ROM replaces Commodore BASIC (C318006-01)
OS92 KERNAL ROM replaces Commodore KERNAL (C318004-0x)

These ROMs do not have tape routines, so they may not be compatible with some copy protection schemes.

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