I'm pretty sure why the BASIC screen cleared after you restarted the machine and performed the SYS command is because by saving up to 033C *exclusive*, you omitted the RTS instruction, so it started executing garbage (likely the BRK instruction). I could be wrong, though; I have only ever saved from a monitor once, and it was from the Super Snapshot monitor.

Absolute legend! Thanks for putting the effort into finding and putting this invaluable bit of code on GitHub. Especially grateful for the usage README, so hard to find historic docs that make much sense regarding the monitor (besides JBs seminal ML text)

Nice overview. Add in the T (transfer aka "copy") and F (fill) commands (I think that's what they are) and you have all the important stuff. One thing I missed back when I used this (or maybe did know and just forgot since) is the J command, which from the look of things JSRs rather than JMPs to the address you give. (I see this eliminates the need to temporarily replace RTS with BRK for routines you intend to SYS to from BASIC, which you'd need to do for the usual G (go) command to work correctly.) One thing I recommend to those who use this (if this works the same as the version I've used) is immediately after first running it, exit back to BASIC and enter NEW to delete the installer. That way if you inadvertently use RUN instead of SYS to restart it, you won't install additional copies and waste memory. This looks like the version I've used, which installs bound to the top of the section of memory BASIC is allowed to use, and moves the top-of-BASIC pointer to just below.

mate can't thank you enough for this, don't know how long I had been trying to figure out how to get the machine language monitor working, thank you for this video, and for the additional commands as well

This is great, thanks a lot for the effort you put into this Monitor and for adding the improvements along the way! I'm 40 years late to this party, but here I am: running the C64 core on my new MEGA65, started up SuperMon+64, and with my printed and spiral bound ML for CBM by Jim Butterfield working my way through learning some ML. Something that I did not understood back in the days.

Thank you for this video, it's very helpful :)

Fantastic program. Thanks for sharing and showing it!

Great video and greate program I can finally start doing ML on my C64 mini (it really does work)...thanks

The JB is just a coincidence that Jim Butterfield wrote the machine language monitor.

Very very nice 🎉

I just spent what feels like hours trying to load SUPERMON+64 into a real (not VICE) Commodore 64. I bought a datassette 1530 from eBay and a cassette adapter to 3.5mm headphone jack, converted the binaries to a wav file that could be played on my phone. I first tried it as an mp3 and got absolutely nowhere--even at a 320 bit rate. Then tried just a straight WAV file and later inverting the wav file (because I saw somewhere that might be a problem). Finally tried flipping the cassette adapter over in the player (to play in the direction it wasn't designed to) and after two or three more attempts, it loaded successfully. Can't remember if the wav file was also inverted or not when it loaded. I would now like to save the program to disk to avoid that headache again. All I know about saving programs to disk on the C64 is saving BASIC programs. How can I use the monitor to save itself onto a floppy? I'm assuming it will be a PRG file that I can execute later. Thanks in advance! -JEJ

In the relocator, what logic went into using $36 as a sentinel value? It seems to be a legal opcode for indexed/zero-page ROL instruction. Is the idea to just avoid using any instructions or data that produce $36 inside supermon? I don't see any reason why we couldn't corrupt the program otherwise. I'm new to 6502 assembly so I'm probably missing something.

Not to be confused with spodermon 64.