New C64 Kernals
(C) - André Fachat
This is Copyright A.Fachat, for distributing use my own License
- 2017-08-13 Added the links to Michael Steil's version of my C64 kernal mods on github, where I also added comments to the code.
Table of content
This is a small patch to allow the C64 to boot an arbitrary file (i.e. "B*") from disk 8 when being Reset. Well, it also does it when doing "stop/restore", but is that a bug or a feature now? The patch is really small, so I only provide the basic executable for it in the file bs-l.s07 and a listing in the file bs-l.s07.txt. To assemble, you have to place my @ASS at $7000 in memory (or somewhere else if you correct the SYS statement). Then you have the modified kernal in the RAM under the kernal ROM.
These kernal ROMs do have a lot more new features than the standard kernal. The place has been taken from the tape routines and the RS232 routines (the latter have been replaced).
These ROMs (esp. version 1.40) have not been tested very well. They surely contain bugs. You are warned.
The ROM images contain copyrighted code - i.e. they are patched C64 ROMs, copyrighted by CBM (or whatever remains of this company).
Note: Michael Steil has taken my kernal modifications and put them up on github, where I have also added comments to them and where they are much more accessible now.
How to use
The C64 patches have quite some history, so everything looks a bit messy. The newest version is 1.40 (of Feb 25, 1997) and has the ACIA serial interface routines replaced by UART 16550A routines.
To assemble the source "BS 1.40.S89,P" (C64 BASIC program) yourself, you have to have my @ASS assembler at $7000 in memory (or change the SYS statements in the source to the correct address). In line 11090 you can change the address of the UART in memory. I have it mapped above the SID, at $d600. In line 12600 you can change the address of the TPI (Tri-Port-Interface) for the Commodore IEEE488 interface. In line 26085 you can change the mapping of the IEC devices to parallel and serial bus. A 0 means parallel IEEE488 bus, a 1 means serial IEC bus. Bit 0 is for device 4, bit 1 for device 5, and so on till bit 6 for device 10. Bit 7 must here be one; device 11 and above are always on the serial bus. If you don't have an IEEE488 interface, leave TPI at $d600 and change the map value to $ff (i.e. all to serial bus). You must have an UART in your computer to use this ROM!
The resulting kernel is then located in the RAM under the kernel ROM. To access it, you have to fiddle around with the processor port (POKE 1, $35). This works, because the BASIC interpreter is also copied during the assemble run :-) You can then save it with a machine language monitor.
The same applies for the version "BS 1.33.S88,P", which has the ACIA routines instead of the UART routines only.
You can change the mapping of the IEC devices by POKE-ing a new MAP value (as described above) to $299.
Archive descriptions
All files with a ".S??" at the end are source files for my selfwritten 6502 Assembler for the C64 (see directory "assembler"). They can be edited as a BASIC file and a RUN makes them assemble, if you have my assembler in the computer's memory (at $7000).
"c64bs2.tar.gz" or "c64bs2.lzh".
"BS 1.*" is a 'new' operating system for the C64 - actually it patches
the original one and has many more features.
1) I have an ACIA 6551 at $d600 (above the SID) in my C64, so the
normal RS232 routines have been exchanged by the 6551 ones.
note that the 6551 has a bug if you use hardware handshake,
disabling the outgoing of RTS/CTS also disables the receiver!
You may loose characters and are warned
2) in the now plenty of free space there is a Function-Key setting,
and a Disk-Command-Line interface. You can load/save a programm
in the directory (without removing "PRG") and standard file
for load/save/shift-run-stop is IEC device 8.
3) I have an additional CBM IEEE488 (the parallel one) Interface on
the expansion port of my C64. Unfortunately the Cartridge ROM
copied itself to somewhere in $cxxx and completely disabled the
serial bus. No use for many programms and if you have two drives
- one parallel and one serial. So I removed the tape routines and
replaced them with the IEEE488 routines. Now you can choose
by a POKE (to ????). The IEEE488 routines don't look that well,
I reassembled them automatically (see another of my tools) from
the ROM (No not, copying copyrighted code ;-). Actually, this only
works with the Commodore expansion, so everyone who has them
should have the right to use this ROM) In the sources in 26080
the default value for the map is loaded, change it to what you
want, a one means serial, zero is parallel, Bit 0 is Device 4,
Bit 7 is device 10, Bit 8 is used to store the actual state.
4) You can now use decimals like "$12ab" in hex, "&234" in octal
and "%001010" in binary format. Some special keys for the
screen editor have been added (Ctrl-Insert, Ctrl-Home and Ctrl-
Crsr-Right)
5) This one has some scroll options (try CTRL and CBM keys in
combination), a Hardcopy-routine (? as far as I see from the
sources, my C64 is packed) and a screen-blanker?
This description is for the latest version,
BS 1.22.S41 is only number 1) and 2).
BS 1.25.S03 is a reengineering from 1.32, it only has ACIA routines,
F-keys, hex/octal/binariy ints, the @-Disk commands but
no tape. especially for a friend of mine who doesn't
have the IEEE488.
BS 1.32.S63 has 1) to 4)
BS 1.33.S88 has all
BS 1.40.S89 has all except 1, but it has serial line routines
for a 16550A UART (with FIFO) instead.
A ROM image for 1.31, 1.32 and 1.40 is included. The ROM images have
the UART/ACIA at $d600 and the TPI at $df00.
BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
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Last modified: 2017-08-13