Questions tagged [commodore-64]

For questions about the different versions and products of the Commodore 64

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28
votes
2answers
3k views

What is the Commodore 64C "France version" and why does it need a beefy resistor?

While perusing the schematics for the Commodore 64C (titled COMMODORE-64 B/NE) I came across a suspicious section of the power supply: The unregulated "9V" is connected to the completely ...
6
votes
1answer
207 views

Commodore 64 sound seems to freeze at a high pitch if executed too soon after startup

I created this little sound driver for sound effects, it makes a classic "laser beam" sound you would hear in old arcade games. There's just one problem, and it's a bit of a strange one. I ...
1
vote
0answers
85 views

How to properly convert an active-low joystick routine to active-high

My last question wasn't specific enough so I'll rephrase it. I've been having trouble with programming game consoles/computers like Commodore 64 that have active-low joysticks, where the bits are all ...
6
votes
2answers
341 views

Flash border color during Kernal LOAD routine

I would like to use the Kernal's LOAD routine to load a file into memory, because that seems to be the easiest way to do it. However, that LOAD call is synchronous in the sense that it returns once ...
6
votes
1answer
199 views

Confusion in the VIC-II registers

I am playing with my old C64 and fiddling with with VIC-II registers. I am using the great Programmer's Reference Guide, but there is something I don't quite get. According to the register map, addres ...
3
votes
1answer
129 views

Spontaneous movement and game crashes from active-low joystick routines [closed]

I've noticed this recurring problem when I'm trying to program joysticks or buttons that are active-low (0 = pressed), like on the Commodore 64 or Game Boy Advance. Regardless of the language or ...
4
votes
1answer
227 views

How to wait for vBlank on Commodore 64

I'm not new to 6502 Assembly but I am new to the Commodore 64. I'm used to the NES where you have to write everything yourself, such as the NMI/RESET/IRQ vectors, etc, but from what I understand the ...
7
votes
2answers
761 views

Basic / Assembler startup code (C64)

I'm just creating my own .prg file using NCurses Hexeditor in Ubuntu which I load using load"file.prg",8 in Vice. I followed the information in this link explaining how to create a .prg file....
5
votes
2answers
478 views

Modern heat sinks for Commodore C64/C128

The VIC-II and SID chips in the C64/128 are prone to over-heating and are rather expensive to replace nowadays. Some other ICs in these machines may have the same issue. An unmodified machine includes ...
9
votes
2answers
690 views

How to repeat a string in C64 BASIC V2?

I would like to achieve the following: I ask for a number from the user, run a loop number times, and in each loop run, output the string like this: -STR$ --STR$ ---STR$ ----STR$ -----STR$ I tried to ...
14
votes
1answer
3k views

Why was the 1541 so slow?

The Commodore 1541 floppy disk drive, sold for use with the 64, was notoriously slow for historical and technical reasons: Marketing insisted on compatibility with the 1540, the floppy drive sold ...
8
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4answers
2k views

How can I implement the modulus operator in Commodore 64 Basic?

How can I implement the modulus operator in Commodore 64 Basic? There are not a lot of math functions to work with, and modulus would be very handy.
6
votes
1answer
417 views

Is this SpeedDOS chip mounted right in my C64?

I have removed a chip to reseat it, but sadly I forgot how it was placed on my C64 (breadbin). I assume its text should be in the same direction of all the other chips on the board, but now I don't ...
22
votes
5answers
6k views

How to detect a real Commodore 64, THEC64, or VICE emulator in software?

Some programs notice if they are run on a real Commodore 64 or an emulator. For example, this demo from 2007 stops on VICE emulator 3.2 with the message "No VIC inside". How is this done? I ...
24
votes
1answer
544 views

How did the C64 lockup bug and its workarounds work?

The Commodore 64 suffered from a strange bug that caused it to lock up when typing in the full-screen BASIC editor. To trigger the bug, position the cursor on the last line of the screen, type enough ...
12
votes
2answers
2k views

Why does the VIC-II duplicate its registers? (C64)

After sporadically reading about the C64 and tinkering here and there for over 32 years I finally decided to get to know my C64 memory layout properly. In doing so I have a question about the VIC-II ...
21
votes
4answers
2k views

Obscure uses of the Commodore 8050/1541 disk drive

When I was working for a foundry consultancy, we did the following Download routines to add delays when writing certain tracks. This was a security feature. When the program started, it would try ...
9
votes
2answers
576 views

How can I connect my Commodore 64 to an RGB+Sync signal via SCART?

I would like to connect my Commodore 64 to my SCART switcher (Shinybow SB-5525), which is connected to a Sony PVM via RGB+Sync. I bought this cable, only to realize after getting it, it is a composite ...
23
votes
4answers
4k views

How was digital sound playback achieved on the Commodore 64?

The Commodore 64 did not have any hardware dedicated to digital audio playback, so how were some games and songs able to achieve this on an unmodified and unextended Commodore 64? Did these ...
8
votes
1answer
706 views

Putting code into two different memory areas with cc65/ca65

According to cc65 / ca65 documentation, the .org directive does not affect the placement of the code unlike with other 6502 assemblers. The docs suggest defining a memory segment with the intended ...
5
votes
1answer
190 views

Why is my Commodore 1541-II stuck showing "Searching for $" whilst trying to load the directory?

I have a Commodore 1541-II drive. I bought this drive used (but like new) a year ago and I used it on my Commodore 64 for about 6 months, but I moved and just reconnected it to my Commodore and it no ...
18
votes
0answers
919 views

Oxford C compiler for Commodore 64

I kept one floppy from my Commodore 128 (which I used mostly in C64 mode), labelled ‘Oxford C compiler’. It is a 5.25″ floppy. Don't ask me why I kept just this one; probably because I thought I ...
0
votes
0answers
51 views

Can I use a Commodore 64 compatible joystick with my Amiga 600? [duplicate]

I have some Commodore 64 compatible joysticks and I would like to know if I can use them with my Amiga 600. I would just plug it in and try it, but I don't want to short circuit anything.
10
votes
3answers
677 views

How do I get the size of a file on disk on the Commodore 64?

As the title, really. I'm reading a SEQ file into memory, and need to know how big it is ahead of time. I know that I can get the size in blocks by parsing the directory, although it's ugly, but the ...
6
votes
3answers
2k views

What are D64, T64, D71 and D81 files?

The docs for the Ultimate-II+ expansion cartridge for the Commodore 64 state: It is able to read D64 files, as well as D71 and D81 files (no partitions), T64 files. So what are D64, T64, D71 and D81 ...
18
votes
1answer
2k views

What's the deal with Commodore's RESTORE key?

Most early microcomputers provided either a dedicated key (e.g. Apple ][), keyboard combination (e.g. PC clones), or dedicated hardware button (countless examples) to "Reset" the computer. ...
6
votes
4answers
623 views

C128D shorted Composite and Ground

I just did a stupid thing and connected a new cable without inspecting it first. It was from a reputable seller, but has shorted pins 2 and 4. What is the potential damage it could have caused and ...
5
votes
4answers
337 views

Running WarpCopy64 on an emulator

I'm interested in IP networking capabilities of the Commodore 64. I learned there is a tool called WarpCopy64 that can be used to run a simple file server on the Commodore. The server can be accessed ...
9
votes
1answer
497 views

Different handling of ASCII interpretation between ca65 and cl65

I stumbled upon a divergence in the ASCII upper case/lower case handling when using assembler and linker of the cc65 suite separately (I used cc65 V2.15 on Win10). For a test I made the following ...
10
votes
5answers
1k views

A game where you program a robot to fulfill missions

I'm looking for a game. Unfortunately there're only few things I remember: You had a robot. There was no way to steer it manually, so to solve a room, every step to do had to be programmed in advance ...
6
votes
2answers
475 views

Does a defacto format exist for Commodore 64 SID music?

I first learned about tracker / mod music on my Amiga in the early 1990's. I remember fooling around with Protracker, listening to mods with Intuitracker, and coming to the realization that all those ...
6
votes
3answers
382 views

New chess engines on retro hardware

Does anyone know of any efforts to write modern chess engines for old hardware? (e.g. C64, A2e?) I'd love to see how a pared-down Stockfish or Leela that could fit in RAM could do rating wise etc. ...
4
votes
2answers
220 views

C64 KERNAL Loading into I/O space [duplicate]

On a Commodore 64, if I Load "*",8,1 and the file's address (first two bytes on disk) is $D000, will it load to the RAM under the I/O space? In other words, does the KERNAL loader properly ...
14
votes
3answers
517 views

Was the Commodore 128 movable zero page / stack and second block of color RAM actually used?

The Commodore 128 hardware allowed two things that weren't possible on the C64: Moving the 6502 zero page and 6502 stack to another place in RAM besides pages 0 and 1, and switching the CPU and/or the ...
3
votes
1answer
663 views

Problems Connecting an Arduino Uno to a Commodore 64 Joystick Port

I have made up a DB9 connector with connections to an Arduino. I am using pins 1 to 4 on the connector. On the Arduino I have a small program which writes out a series of digital HIGH signals to the ...
2
votes
1answer
342 views

What is the file that VICE refers to as dos1541?

VICE needs a file called dos1541 if you want hardware emulation of the 1541 disk drive. What does that file contain, exactly? The 1541 seems to have two ROMs: a DOS and a KERNAL. But if I take the ...
9
votes
4answers
703 views

Delay loop in BASIC

Yesterday I was looking for a way to implement a delay loop on the C64. I came across this page: https://www.c64-wiki.com/wiki/TIME At the bottom of the page there is a code fragment that waits for a ...
2
votes
0answers
111 views

Running Codenet on a Commodore 64 Emulator

I finally managed to get basic networking stuff working on VICE, thanks to another thread on Retrocomputing. I'm now wondering how to setup a Codenet server emulation. I was able to identify four ...
1
vote
0answers
48 views

How to Perform RR-Net MK3 Detection on VICE Commodore 64 Emulator?

RR-Net documentation describes a detection algorithm for the MK3 model. The algorithm is supposed to reveal the last four hex digits of the MAC address. According to documentation the MAC address 28:...
8
votes
3answers
1k views

How to transfer files to C64 emulator quickly

I just discovered the fun of writing small programs (Basic/asm) for an emulated C64 for me. Unfortunately, I cannot get used to the emulated C64 keybord, and would like to write the programs on the ...
6
votes
1answer
180 views

Chaining IRQ's with BASIC & Kernal routines turned off

Having disabled BASIC and Kernal routines I set up an IRQ to run the following code when the raster line reaches 200: .irq1 inc 53280 // change border colour // lda #$ff // clear the ...
7
votes
2answers
828 views

Does the Commodore 64 power switch have a history of failing?

My original (1983?) Commodore 64 (brown breadbox with grey function keys) has trouble powering on. Specifically, when I flip the power switch the power LED will glow dimly and the machine fails to ...
7
votes
2answers
950 views

Does anybody remember a database cartridge for the Commodore 64?

Decades ago I bought a database cartridge for my C64. IIRC it was a no-name brand being sold as close-out or from a bargain bin. It may have been the slowest program I ever bought. It wasn't too ...
35
votes
7answers
13k views

Why did Commodore 64 cartridge games disappear?

The Commodore 64 has a cartridge slot, but by the mid-eighties, cartridge games disappeared; everything was on tape or disk. Why? One answer that suggests itself is that by that time, a larger ...
7
votes
3answers
547 views

Is it still possible to access a BBS via dial up internet on the C64 (or other retro computers)

I was wondering if it is still possible to access any online BBS using dial up and an 80's era computer. I'm aware that some dial up internet providers still exist (eg Nippy Internet in the UK), but ...
3
votes
2answers
359 views

What high nibble values can you get when you read the 4 bit color memory on a C64/C128?

The C64 and the C128 have a memory for storing the color values of a character. The size of this memory is 1k x 4bit (2k x 4bit for the C128 which can do a double buffering), thus reading the value at ...
3
votes
3answers
634 views

What are quick ways to load downloaded tape images onto an unmodified 8-bit computer?

There are repositories of tape software available online, for example CPC Power for Amstrad CPC machines. What is the fastest and simplest way to load such games onto an unmodified computer, with the ...
12
votes
1answer
1k views

Identifying this 6502 Assembler

I found some 6502 assembler code for a Commodore 64 program that uses meta commands like #include "foobar", define the address to be assembled to via *=$1234 and define labels without a colon. ...
6
votes
1answer
529 views

Bank switching and memory perspectives (C64)

I've been reading up on bank switching on Wiki and in particular here which contains the below nice image and have a few questions: Am I right in thinking that LOAD loads into RAM (dark grey in the ...
0
votes
3answers
236 views

c64 copy chars to sprite issue

How to do correct copying char to sprite ? Lets say 1st char is at $2000 second is at $2008 and copying to sprite at $2480. And with this we can copy 1 char to top left position of 1st sprite. But ...

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