Questions tagged [commodore-64]

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

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Synchronising FOR - NEXT routines in C64 basic [closed]

I am writing a program which has an ASCII background, animating character moving to random locations, and finally adding music It's my first ever C64 attempt and I want to finish it in BASIC before ...
Journeyman1234's user avatar
18 votes
4 answers
3k views

Commodore 64 - any way to safely plug in a cartridge when the power is on?

Back in the early 1980s when my friends and I all had Commodore 64s, we all knew never to plug a cartridge in with the power on. I once got a tape from someone with lots of utility programmes, one of ...
Alan B's user avatar
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10 votes
1 answer
569 views

Problem using Commodore 64 BASIC TAB() command in abbreviated form

I’ve encountered a bug on the Commodore 64. When I write out the full TAB command, i.e., TAB(…), everything works as expected. However, when I use the abbreviated form, tA, an extra parenthesis is ...
user10969003's user avatar
8 votes
1 answer
1k views

C64 char screen plot routine - not clear about reason for logical OR

I'm trying out some 6502 assembly language, specifically using Kick Assembler. I have the following routine that just sticks a character on the text screen at a specified x and y, it's taken from the ...
Alan B's user avatar
  • 4,055
9 votes
1 answer
446 views

Sending DOS commands in assembly on my C64

Consider the following Basic program for the C64. 10 OPEN 15,8,15 20 PRINT#15, "I" 30 CLOSE 15 This classic gem simply opens the 'command channel' and sends the DOS 'init' command to the ...
Geo...'s user avatar
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1 vote
1 answer
215 views

Commodore 64c supply 9 Vac waveform specs

I found an old Commodore 64c without a box, cable, or anything else and I want to put it back to work. In order to do so, I need to turn it on to see if it works. I've already found the pinout of the ...
jack07Code's user avatar
12 votes
2 answers
2k views

What is this unusual syntax for the Commodore SYS command?

I was recently interested in how to 'bload' some data on my commodore 64. For the sake of discussion the data isn't really relevant (it could be any blob of bytes). Generally you can load a file into ...
Geo...'s user avatar
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0 votes
1 answer
142 views

Monitor connector for C64 and ST the same?

I have a monitor (colour) that works on my Atari ST. The connector looks similar to that of my Commodore 64, but it doesn’t seem to fit. Now I don’t know if I just have to use a bit more force, or ...
ABM K's user avatar
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1 vote
1 answer
231 views

Interfacing with the Commodore 64 IEC Serial Port using Assembly

I'm struggling a bit to find relevant documentation on this subject when it comes to using just assembly. All I've found is either irrelevant or for BASIC. My goal is to be able to send and receive ...
SkyeG06's user avatar
  • 21
25 votes
1 answer
4k views

Why does the Commodore 64 have 4K of non-banked RAM at $C000?

I wonder why the Commodore 64 memory map was created as it was. Naively, it seems to be that it would have been more logical to put I/O and the character ROM at $B000 to $BFFF, have the ROMs in a ...
TeaRex's user avatar
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15 votes
2 answers
3k views

Were cartridge slots cheaper at the back?

I'm remembering a difference in the design of Commodore computers like the Vic and 64, versus the Atari 8-bits, and game consoles from the likes of Atari and Nintendo: they all had cartridge slots, ...
rwallace's user avatar
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11 votes
1 answer
304 views

Commodore 64 breadbin plastic stands repair options?

I have a Commodore 64. The internal plastic stands for the board were all cracked and some were completely destroyed. See pictures In a futile attempt to fix them, I removed the old broken ones, ...
Stefano Borini's user avatar
15 votes
3 answers
3k views

Difference between machine language and machine code, maybe in the C64 community?

I've always been sure that "machine language" and "machine code" are totally synonymous and mean programming directly in the language the machine understands, whether in binary, ...
hippietrail's user avatar
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10 votes
4 answers
3k views

Assembly delay function for C64

I've written a delay function that simply counts the times the screen raster line reaches a particular value. // zero page addresses .const delayFrames = $00fa .const delayCounter = $00fb // =...
Gavin Williams's user avatar
4 votes
4 answers
523 views

Looking for old C64 game with "thriller" plot

In the late 80s (1989...) I had a C64, I bought some magazine about videogames. In one of this I read about a "thriller" game, in which you must discover the assassin in a house, I recall a ...
elbarna's user avatar
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5 votes
2 answers
467 views

Printing characters not at expected position

Simple program... 10 print chr$(147);chr$(5) 20 poke 53280,4: poke 53281,0 30 y=0 : for x = 1 to 35 40 poke 214,y : print : poke 211,x 50 print chr$(171);chr$(177);chr$(179); 60 next x : print : print ...
Gavin Williams's user avatar
19 votes
3 answers
2k views

Why was the VIC-II restricted to a hard-coded palette?

The MOS VIC in the VIC-20 and the MOS VIC-II in the C64 were capable of outputting 16 colours drawn from a hard-coded palette. It's clear that the palette size was fixed at 16 colours as a memory-...
Psychonaut's user avatar
  • 7,133
2 votes
1 answer
304 views

How to fix the inaccurate mouse movement in the Eye of the Beholder for C64 under VICE? [closed]

I'm trying to play the C64 and C128 versions of the Eye of the Beholder by using the VICE emulator on Windows 11, but the mouse movement is too inaccurate and it constantly flutters on a moving ...
bobeff's user avatar
  • 563
5 votes
1 answer
354 views

Why can't the VIC-II handle ECM and Multicolor at once?

On the Commodore 64 there are a few different graphical mode selection bits we can enable. This question is about three of them: Multicolor mode (hereinafter MCM), where pixels are joined pairwise ...
Omar and Lorraine's user avatar
13 votes
2 answers
729 views

Why does the FRE() function in CBM BASIC v2 return negative values?

On Commodore machines featuring CBM BASIC v2, the FRE() function to query the amount of memory available to BASIC returns a negative number when the result exceeds 32767 bytes: This quirk does not ...
Psychonaut's user avatar
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5 votes
0 answers
175 views

What percentage of the SID was control versus voices?

I'm interested in specifics of the design and manufacturing of the SID, the sound chip of the Commodore 64. There is a good die photo here http://www.visual6502.org/images/8580/...
rwallace's user avatar
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9 votes
1 answer
453 views

Are the 16 linear steps of the SID Sustain and Filter Volume/Resonance steps of 6.25 or 6.666666667?

The SID has various registers that are described as 16 linear steps: The Filter Volume, The Filter Resonance, and the Sustain of the voice envelopes. The SUSTAIN levels range from zero to peak ...
Michael Stum's user avatar
  • 1,670
22 votes
6 answers
3k views

Did home computers have mechanical interfaces to typewriters?

In the April 1985 issue of Ahoy!, a reader asks whether it is possible to hook a conventional typewriter up to his Commodore 64. Surprisingly to me, columnist David Barron answers that such ...
Psychonaut's user avatar
  • 7,133
2 votes
2 answers
778 views

Software to generate C64 BASIC code printing PETSCII art

I am looking for a good toolkit to auto-generate C64 basic code, which eventually prints different PETSCII graphics. I am wondering, if there is a good workflow for this, e.g. using a graphical ...
philipp_b's user avatar
12 votes
3 answers
2k views

Commodore 64 noises during loops, flash load and others

When I was a child, I had a Commodore 64 always connected to a TV via the RF Out. I remember that when running a BASIC program, there were certain noises to be heard. Especially when a longer FOR loop ...
rexkogitans's user avatar
2 votes
2 answers
269 views

How do I save data from a program with CC65 [closed]

I wanted to have a calculator program be able to save a set of answers on a floppy disk or tape but I have no idea what I should do. I am aware that the "cbm.h" library can be used to load ...
Mr Buddyboi's user avatar
4 votes
1 answer
917 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 ...
Keltari's user avatar
  • 503
1 vote
0 answers
167 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 ...
0xF2's user avatar
  • 365
2 votes
1 answer
364 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 ...
Digerkam's user avatar
  • 311
6 votes
1 answer
713 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 ...
Pitto's user avatar
  • 243
1 vote
1 answer
187 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 ...
Pitto's user avatar
  • 243
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 ...
Jeroen Jacobs's user avatar
7 votes
1 answer
464 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 ...
scrØllbær's user avatar
  • 1,109
8 votes
1 answer
690 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 ...
Robin Elvin's user avatar
17 votes
1 answer
467 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 ...
Psychonaut's user avatar
  • 7,133
9 votes
2 answers
1k 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 ...
wizofwor's user avatar
  • 2,758
11 votes
1 answer
273 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 ...
GrapefruitIsAwesome's user avatar
4 votes
1 answer
296 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 ...
cjs's user avatar
  • 25k
2 votes
1 answer
262 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 ...
puppydrum64's user avatar
  • 1,638
2 votes
1 answer
444 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 ...
elbarna's user avatar
  • 1,739
8 votes
0 answers
341 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 ...
elbarna's user avatar
  • 1,739
18 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 ...
rwallace's user avatar
  • 60.2k
6 votes
8 answers
1k 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 ...
komodosp's user avatar
  • 1,056
8 votes
1 answer
1k 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 ...
user1095108's user avatar
17 votes
3 answers
5k 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 ...
Bart Friederichs's user avatar
18 votes
3 answers
2k 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 ...
Simon's user avatar
  • 283
31 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 ...
pipe's user avatar
  • 1,718
2 votes
2 answers
349 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 ...
puppydrum64's user avatar
  • 1,638
6 votes
2 answers
487 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 ...
Cactus's user avatar
  • 2,670
6 votes
1 answer
281 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 ...
puppydrum64's user avatar
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