Questions tagged [commodore-64]

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

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3 votes
1 answer
748 views

Commodore SX-64 White screen

I recently acquired a Commodore SX-64. It powers on, but the CRT just displays a white screen. I dont have a test cartridge yet, not that it would help as thereis no display. I havent tried an ...
2 votes
2 answers
330 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 ...
10 votes
2 answers
797 views

What pointing devices were available for C64/C128?

Apart from 1351 mouse what other official Commodore C64/C128 pointing devices were available, or notable 3rd party like Mouse Cheese. Joysticks and controllers are out of question. C64-wiki seems to ...
10 votes
2 answers
13k views

Best path to learn C64 assembly [closed]

The amount of tutorials, youtube videos, scanned books on C64 programming is overwhelming. What materials would you recommend -- and, importantly, in what order! -- to build a path to programming my ...
1 vote
0 answers
102 views

Telnet BBS — server side with Synchronet [closed]

I have restored a Commodore 64 and equipped it with a "WiFi modem", which allows me to connect to Telnet BBS sites over the internet. So far so good for the client side. Server-side, I am ...
57 votes
2 answers
12k views

Why did Commodore fill their power supplies with epoxy?

If you know anything about the Commodore 64 (and other Commodores, really) you know that Commodore really went the cheap route and produced some awful power supplies. The Commodore 128 PSU isn't ...
20 votes
5 answers
1k views

Why the disparity between the screencodes and the character codes?

The Commodore 64, and possibly others, I don't know, have character codes (These map integers to characters, in the same way that ASCII does) and there are screen codes (The offset which the VIC-II ...
20 votes
5 answers
2k views

What is the history of DE-9 joystick ports?

The Commodore 64 and the Atari 2600 had compatible joystick ports. Commodore, Atari, and third-party companies like Wico made joysticks supporting that standard. Did this standard have a name? ...
9 votes
2 answers
771 views

Did Commodore ever produce gray colored Commodore 64?

The Commodore 64 was produced for a 12 years from 1982 to 1994. It had several iterations of case color, keyboard color & keyboard labels, badge etc. Commodore was famous for using whatever parts ...
2 votes
1 answer
276 views

Obtaining a CPU execution trace on a Commodore 64 [closed]

I need to collect the execution trace of all instructions executed by the 6502 on a C64. I tried C64 Debugger, but I couldn't find any option for this. Is it possible to obtain with C64 Debugger? Are ...
10 votes
1 answer
234 views

Commodore / Apple II GEOS Document Cross-Platform Compatibility

As I have never used Graphic Environment Operating System (GEOS) on an Apple II (only I on a Commodore 64), I have always wondered were the documents created (from programs such as GeoWrite and ...
6 votes
1 answer
324 views

How should I set CCGMS on my Commodore 64 to login to a Linux machine?

I have a Strikelink WiFi modem for the C64 (see here and here) and I can connect to a BBS without issues using CCGMS 2017 v4 and the following settings: Baud = 9600 Modem Type = UP9600 / EZ232 For ...
33 votes
13 answers
13k views

Did computer games for Commodore 64 really take "25 minutes" to load "if everything went alright"?

In the Swedish-language song "Nostalgi" by Markoolio from 2003, some of the lyrics go: My first computer had 64 kB you surfed on the water, and that's that The computer games were loaded ...
20 votes
6 answers
3k views

Does lossy audio compression damage datasette data?

I grew up with the C64 and had software on cassette tapes. These days, you can find "backups" of this software all over the internet, even in mp3 format (by recording the audio signal with a ...
1 vote
1 answer
136 views

How to send and receive messages between modern computer and Commodore 64 via WiFi? [closed]

I want to be able to connect from my Commodore 64 to a Linux Raspberry Pi. The ideal solution would be something like ssh that allows me to use the linux machine using the c64 as a terminal but the ...
4 votes
1 answer
226 views

Are SID Players practically almost full-fledged C64 Emulators?

There are many stand-alone audio players (and plugins for general audio players) out there for many systems that play the music of the Commodore 64 that is famous for its SID chip. I believe many of ...
17 votes
1 answer
367 views

Was any commercial end-user software written in PROMAL?

PROMAL is a procedural programming language from the 1980s. Its designer, Systems Management Associates, released compilers for the Commodore 64, Apple II, and IBM PC. The language and development ...
13 votes
1 answer
1k views

What is the exact bus protocol used by the C64/C128 REU?

The Commodore 64/128 RAM Expansion Units used a DMA controller to move data between the REU's RAM and system RAM (or I/O space). One would set the addreses, length and direction for the transfer (or ...
8 votes
1 answer
261 views

How does the VIC-II/CPU memory access work on the C64?

As a programmer I knew that on the C64 the CPU got the bus in the high phase of PHI2 and the VIC-II got it in the low phase and also stole extra high phases when required. However, it wasn't until ...
0 votes
0 answers
236 views

Identify this old C64 soccer game with "speaker"

In "modern" games (Fifa 98, Fifa 2000, PES, etc) you can hear the speaker talking about the match. This was near impossible in the C64 era, but I remember a soccer game that had a speaker ...
47 votes
5 answers
6k views

Why are C64 games inconsistent with which joystick port they use?

The Commodore 64 has two DE-9 joystick ports. If I'm the only person that ever plays games on it, you would assume that you could just leave a joystick plugged into Port 1 and be done with it. However,...
23 votes
1 answer
2k views

When does the VIC-II read the sprite data?

This question is about the Commodore 64 and its graphics chip, the VIC-II. Imagine that on a particular scanline, the VIC-II needs to fetch 40 bytes (the background tiles) and since it's a badline ...
2 votes
1 answer
195 views

Timer B Interrupt occurs only once

I was following this tutorial on Commodore 64 timer interrupts and tried to replicate it (except all I was planning on doing was changing the border color.) I noticed that my interrupt only occurs ...
23 votes
8 answers
4k views

Why did the VIC-20 and C64 have only 22 and 40 columns when the earlier PET had 80 column text?

When I was a kid, the "real" computers in movies looked so cool with that 80-column monochrome green text. My first computer was a VIC-20 and it always felt very "toy-like" to me ...
2 votes
1 answer
173 views

Does C64 /DMA assertion immediately disconnect the CPU from the address bus?

I have heard several claims (in the comments on this question and answers) that asserting the D̅M̅A̅ signal on the Commodore C64 cartridge port will immediately take the CPU off the bus by deasserting ...
5 votes
0 answers
193 views

Identify C64 Game About Firemen

I'm searching for an old game for the C64, it was about a group of firemen. I last played it in the 1989, 32 years ago, so I do not remember it very well. I remember only that the firemen don't want ...
22 votes
1 answer
2k views

How does the C64 get an accurate TOD clock on both 60 Hz and 50 Hz power?

The C64 has two Time of Day (TOD) clocks, one in each of its 6526 CIA chips U1 and U2. These calculate time based on a 60 Hz or 50 Hz input to the TOD pin (pin 19); the clock input frequency assumed ...
9 votes
1 answer
379 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 ...
17 votes
3 answers
4k views

How can I store a machine language program to disk on a C64?

I know I can use LOAD "PROGRAM",8,1 to load a program in a certain spot in memory, using the first two bytes of the file on disk. Now let's say I have used the .MON command on the Final ...
21 votes
3 answers
6k views

6510 clock rate of C64: Why was it considerably slower than the 6502 of the Atari 800?

According to Wikipedia, the Atari 8 bit series had a 6502 running at ~1.8 MHz. Why was the clock speed of the 6510 for the C64, which was designed a couple of years later, considerable slower? Was the ...
17 votes
3 answers
5k views

How did the Commodore 64 show a picture while reading cassette?

I was watching this video just now https://www.youtube.com/watch?v=I0YmJluYb6Q&ab_channel=NostalgiaNerd on things that early home computers displayed on the screen while reading cassettes, and ...
11 votes
2 answers
1k 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 ...
19 votes
3 answers
1k views

Can a Commodore 64 use two screen modes on one scanline?

Many games, for example, Maniac Mansion, or Kissenschlacht, use two screen modes. Oftentimes, a bitmap mode for the main screen, and a text mode for the lower part which displays scores or whatever. ...
6 votes
8 answers
679 views

Would a multi button controller have been possible on the C64?

One thing I felt letdown the C64 for many games was the lack of multiple buttons on the joystick, meaning you had to keep the keyboard nearby, (or by your foot!) So you could press space-bar or ...
8 votes
1 answer
768 views

Why was Carrier Command for the ZX Spectrum superior to the C64 version?

The ZX Spectrum version of Carrier Command has 3D rendering, while the Commodore 64 version, despite a greater amount of RAM, was inferior in comparison. You open the in-game map and there's Google ...
14 votes
2 answers
1k views

How did the Sinclair compare on price with the C64 in the UK?

As far as I know, the popular low-end home computers in the UK around the mid-1980s were the Sinclair ZX-Spectrum ("Speccy") and the Commodore C64. I know the BBC micro also had a following, but my ...
4 votes
2 answers
540 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 ...
17 votes
3 answers
1k views

6502 ORA not updating the accumulator

Unless I'm reading the manual incorrectly, the following should produce $11 when D404 = $10 (I'm turning on the gate for voice1 which has been previously set to triangle wave %00010000/$10) 00153 ...
29 votes
2 answers
4k 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
1 answer
261 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 ...
6 votes
2 answers
399 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 ...
3 votes
1 answer
136 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 ...
8 votes
2 answers
1k 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....
7 votes
2 answers
903 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
2 answers
857 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
1 answer
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 ...
10 votes
4 answers
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
1 answer
450 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
5 answers
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
1 answer
853 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 ...

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