Questions tagged [commodore-64]
For questions about the different versions and products of the Commodore 64
5
votes
1answer
242 views
How did the C64 interface tape drives?
How did the C64 interface tape drives?
I'm aware that the external interface was basically a audio input - but how was this audio converted into digital data, and how was it loaded into RAM and ...
1
vote
1answer
64 views
Is it possible to switch the interrupt source of the C64 to VIC without changing the IRQ routine?
The ROM IRQ routine at $EA31 is usually trigggered by the timer interrupt 60 times a second. Is it possible to switch the interrupt source to VIC and still use the same routine? If yes, which memory ...
4
votes
2answers
150 views
How to exactly sync to the raster line for a vertical raster split?
Motivated by Wilson's question Can a Commodore 64 use two screenmodes on one scanline? I tried to implement a simple example that polls the beginning of a rasterline and then switches the screen mode ...
2
votes
2answers
255 views
When were sprites first displayed in the border area?
I assume one of the first undocumented effects on the VIC-II was the ability to display sprites in the (upper and lower) border area. I wonder how and when this was first discovered and used? Was it ...
4
votes
2answers
239 views
Why does the Commodore 64 leave these pointers in Zeropage?
I'm trying to decide on what I can get rid of from the zero page, so that I can keep my own data there. Looking at this page, documenting what each of the zeropage locations do, I'm trying to figure ...
5
votes
2answers
259 views
Commodore 64 with red and white RCA cable
After discovering my old Commodore 64 in the garage, I wanted to test if it still works. The power light comes on but the video connection to a modern TV is obviously an issue, as mentioned here. Well ...
12
votes
2answers
558 views
Why was BASIC on the Commodore 64 one byte shy of 38KiB?
When you power up a Commodore 64 you are greeted with a friendly message telling the user it has 38911 BASIC bytes free. 38,911 is one byte shy of a 38 KiB (1,024 * 38 = 38,912).
What was the reason ...
1
vote
1answer
153 views
How to read disk files using CBM specific functions in cc65 with proper error checking
TL:DR
What is the reason my kernel_read() function ignoring file errors?
I'm trying to understand how to work with files in cc54 using CBM specific functions. My target is Commodore 64 with 1541 ...
11
votes
2answers
773 views
Does the Commodore 64 have the PHX opcode?
Code written for the Commodore 64 sometimes uses the PHX opcode, which should push X onto the stack. There also are plx, phy, ply. These were apparently added on the CMOS versions of the 6502; very ...
1
vote
2answers
272 views
Using C64 floating point kernal routines with 16 bit integer
How to use floating point kernal routines for 16 bit arithmetics such as: $1234*$ABCD or $1234/$ABCD ?
4
votes
2answers
187 views
Method for adding firmware to a Commodore 64 expansion card?
The C64 expansion port can and does support multiple IO devices without conflicts. There is 0.5 KiB that is decoded for $DE00-$DFFF, using /IO1 and /IO2 on the expansion port. As long as the devices ...
13
votes
1answer
269 views
C-64 Exchange News Service
I am trying to recall the name of a peripheral I use to have for my C64 in the 1980s. I believe it was called Exchange or X-Change. You hooked it up to your cable TV service and it would decode a ...
8
votes
2answers
364 views
6510 I/O port initialisation
TL;DR: With what values are the I/O port registers (locations $00 and $01) on the 6510 initialised when it is powered on?
I'm writing a Commodore 64 emulation. The Commodore 64 uses a 6510 ...
2
votes
1answer
160 views
Audio from Commodore 64 to line 1/4 inch line level
I have a 1702 monitor for my C64. I use a cable that splits the video/audio from the C64 to the Red/Yellow/White thing. Something like this. The white cable is the audio. I believe this is an RCA ...
8
votes
2answers
607 views
Why did certain color combinations look terrible on the Commodore 64?
As I recall, on the Commodore 64's text mode, if you chose certain colour combinations, the letters would be badly obscured by some kind of interference which seemed to affect each character cell ...
2
votes
1answer
108 views
Can't enable list even with “enable run-stop” poke
Well, I've downloaded an old non-English textual adventure, which of course, "for the sake of professionalism" have list disabled. Even after entering pokes for enabling "run-stop/restore" and for ...
13
votes
2answers
368 views
Can a Commodore 64 use two screenmodes on one scanline?
Many games, for example, Maniac Mansion, or Kissenschlacht, use two screenmodes. Oftentimes, a bitmap mode for the main screen, and a text mode for the lower part which displays scores or whatever. ...
17
votes
2answers
592 views
What's a good way to implement this “splashing water” effect on the C64?
This pillow fighting game set in Venice
depicts the two opponents fighting on a wobbly gondola on a canal. It was apparently known as "Pillow Fight" in English and as "Kissenschlacht" in German, and ...
6
votes
2answers
318 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 ...
4
votes
3answers
553 views
How can I view BASIC code hidden by SYS?
I ran a validation of an old disk, and it turns out this ruined a game (won't load) and deleted my old high score list on David's Midnight Magic. I would like to edit the code to get the high score ...
5
votes
1answer
391 views
Copying disk images to Commodore 64 floppy disks
For some time now I have been on a mission to get back into playing games on a Commodore 64. I have bought an original Commodore 64C. I got hold of a original 1541 disk drive. I also got hold of a ...
10
votes
3answers
2k views
Visible resolution of C64 video output, including borders
The VIC-II in the C64 outputs 320x200 pixels inside the borders. What is the full visible resolution including the borders?
To clarify, I am interested in the full screen size in units of normal ...
5
votes
1answer
290 views
1980's ROM used which exp(n) algorithm?
In 1980's ROM (Apple IIe, Commodore 64, VIC-20, ...) which algorithm is used to compute exp(x), and where do the coefficients below come from? (Chebyshev, Remez, Pade, ...)
.byte $71,$34,$58,$3E,$...
3
votes
2answers
1k views
Why do they use CLI in an IRQ routine?
I am studying an FLI routine in http://codebase64.org/doku.php?id=base:fli_displayer and I noticed that the CLI instruction is being used in this IRQ routine:
irq0: pha
...
cli ; &...
5
votes
2answers
391 views
Open source, non-GPL SID emulator
I am looking for a SID emulator that is open source, but not GPL. In particular, I am looking for something with a license that allows me to link it to a closed-source program; and also one that ...
3
votes
2answers
116 views
How can I view an Error Info Block in a D64 image?
I've been imaging old C64 floppies using a 1541 disk drive connected to my old Pentium III via a homebrew parallel cable and the Star Commander. Given that my disks are 30+ years old, I am amazed ...
1
vote
1answer
425 views
Where to buy an 8 bit computer remake? [closed]
I want to buy a remake of an 8-bit computer, e.g. the ZX-Spectrum or c64.
Must haves:
Modern monitor output(e.g. HDMI)
Modern keyboard, no gum keys
Modern storage, e.g. SD card or USB stick, etc...
...
6
votes
2answers
675 views
Is it possible to bank out Kernal in Commodore PET, VIC-20 or 264 series computers?
You can bank out Kernal ROM in C64 using $01 register. This was preferred by game/demo coders who wants to employ self tuned routines and wants to expose ram 'underneath'.
You can do lda #$35 : sta $...
9
votes
1answer
264 views
VIC-II transistor count
I'm curious about the transistor count of the VIC-II, the video chip in the Commodore 64. According to http://visual6502.org/wiki/index.php?title=Chips_in_our_collection the Atari 2600 TIA chip has ...
8
votes
3answers
926 views
How to spin up 1541 drive without C64
I have a 1541 drive and I want to make it spin but I don’t have a Commodore computer. I don’t need to read data, I would just like the drive to spin. Can I manually tell it to spin using a raspberry ...
32
votes
7answers
9k 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 ...
0
votes
1answer
390 views
Is it possible to make VICE load .prg files faster?
When I load a C64 .prg with the Hoxs64 emulator, my .prg loads pretty much instantly.
But when I load the same .prg file with VICE (x64 app.prg) it takes quite a while (depends on memory map, but ...
15
votes
1answer
298 views
How to create a switchless multi-system 2 button Atari joystick?
All systems that use the Atari 9 pin joystick standard make use of the following pins in consistent ways, with each direction and the fire button being connected to the ground pin when pushed.
1 - up
...
2
votes
1answer
162 views
Is it possible to use the BRK instruction when ROM is banked out?
I used to use the BRK instruction when debugging on the C64.
However, when I bank out ROM with...
lda #$35 // Bank out kernal and basic
sta $01 // $e000-$ffff
...the BRK instruction (...
12
votes
3answers
2k views
What's a good way to implement this “fade” effect on C64
See the beginning of https://www.youtube.com/watch?v=hmfLBAtGAKk. Here's a screenshot:
It basically clears characters pixel by pixel both horizontally and vertically.
Use sprites for the pixel by ...
1
vote
2answers
377 views
Reading both keyboard and joystick with non-KERNAL code on C64
I'm implementing non-KERNAL joystick and keyboard controls for my Commodore 64 game.
I used to use the KERNAL SCNKEY routine earlier to read keyboard and it worked well with my joystick port 2 code. ...
4
votes
2answers
354 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 ...
3
votes
3answers
820 views
Recovering old commodore 5.25" floppy disks
I am noob to all of this, I am trying to relive my childhood.
I picked up a commodore 64 with about 1,500 floppy disks. Many of them are de-magnetised and there is currently only one disk I can run (...
3
votes
2answers
247 views
Commodore VIC-20/64/128/16/Plus 4 floppy disk drive replacement
We all know that floppy disks are getting hard to find, and floppy drives are fragile to begin with (especially Commodore's 1541 drive). I know that several companies and parties have released floppy ...
12
votes
1answer
712 views
Why does the C64 have the following palette?
The Commodore 64 has the following fixed palette of 16 colours:
(Your palette may vary due to tuning of screen, etc.)
What was the reason for this selection of colours? Are these colours ...
14
votes
2answers
2k views
Is the s-video output on the Commodore 64 different from “normal” s-video?
I saw Commodore 64 to modern TV about how to connect the Commodore 64 to a modern TV. I don't understand all the details of the answer, so I wanted to try and ask something specific here.
In short, I ...
5
votes
2answers
524 views
Getting your Commodore VIC-20, 64 or 128 online
Back in the day, of course we used modems ("dial-up modems" in today's parlance) to get our Commodores connected to other systems.
These days I know several people have concocted options to get ...
9
votes
4answers
2k views
Who wrote the MS BASIC on the PET/C64/etc?
I'm wondering if anyone has a document that describes the history of the BASIC interpreters used in the various Commodore 8-bit machines?
Ultimately I'm trying to track down how it is that the A% ...
22
votes
1answer
4k views
Why do all the Speech Synthesizers have that same Voice?
The first time I ever played with software speech synthesis on a microcomputer (not hardware synthesis, like in TI's Speak & Spell) was around 1983, using S.A.M for the Commodore 64.
A year later,...
5
votes
2answers
3k 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 ...
2
votes
2answers
458 views
How can a C64 interrupt let the KERNAL keep operating?
I am working on a loading screen, and what I wanted was a simple raster trick (just change the border colour on the bottom half of the screen),
and also call the KERNAL to load some more data from a ...
5
votes
1answer
267 views
Is there a MIME type for C64 .PRG files?
I'm writing an emulator with an HTTP API that could usefully accept C64 .PRG files as the request body of a POST request. This means it has to be able to detect such files by their MIME type: POST ...
7
votes
2answers
250 views
Behaviour of $D000-$D3FF section on the C64 during bankswitching
My question is about bankswitching behaviour on the Commodore 64.
I'm writing a C64 game for a 16kb cartridge with EXROM and GAME pulled low, so the available bankswitching modes are (according to ...
10
votes
1answer
365 views
Go program for the C64
Is there a program for the C64 that plays the game of Go? Progress on go engines has started later than with chess, so maybe there is no C64 Go software from the 80s, but maybe someone has recently ...
6
votes
2answers
644 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 ...
