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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 ...
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 ...
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 ...
13
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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. ...
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 ...
9
votes
6answers
841 views

Is there a C64(or any other) emulation that can be run in terminal?

I was looking for a C64 type computer that can be used in the terminal. Can I code one or is there one on the interwebs?
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 ...
27
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2answers
3k views

C64: Why is POS(π) faster than POS(0)?

According to this article: german C64 Wiki article about the POS() command POS(π) is 20 % faster. Although in my experience it is ...
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 ...
12
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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 ...
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 ...
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 ...
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,...
10
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3answers
769 views

Why did blanking of screen on C64 SAM enable better quality speech synthesis?

There's this old piece of software still present in today's Windows called SAM that enabled C64 to speak. I remember that we could choose either screen on and worse speech quality or screen off and ...
11
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3answers
1k views

How do serial (user port) adapters achieve speeds above 1200bps in C64?

The information I have states that the userport' serial speed is about 1200bps, but there are some carts going up to 9600bps. I would imagine that the 1200 is the limit, so I'm wondering how is the ...
16
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4answers
1k views

What graphical effects can be created by changing the VIC-II settings?

I read in this answer that one could create graphics effects outside the usual specifications of the hardware by changing the settings of the machine's VIC-II at specific cycles during the video ...
22
votes
2answers
1k views

Why does waggling the joystick of a C64 cause errors loading from tape?

When loading a game from the tape drive on a C64, if you wiggle the joystick around too much the program will not load correctly. Is there an explanation for this? EDIT: Perhaps someone can try to ...
27
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2answers
1k views

Why does the C64's LIST command choke on REM statements with a Shift+L?

On the Commodore 64 and VIC-20, the LIST command will abort with a ?SYNTAX ERROR on any line that contains a REM statement with a Shift+L character. A minimal program triggering the error would look ...
14
votes
3answers
862 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? ...
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 ...
10
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4answers
754 views

C64 BASIC: How to suppress the '?' sign when using the INPUT command?

When you are getting INPUT in Commodore BASIC it always adds a question mark at the end of the string you want to show. Is there a way to suppress the question mark when using the INPUT command?
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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 ...
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 ...
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 ...
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
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 ...
12
votes
4answers
694 views

How to use BASIC after “LOAD ”$",8 on the C64

After loading a file list from a floppy disk it is hard to program in BASIC because the file list is interpreted as BASIC lines. For example there can be 20 lines with the number 1, because 20 files ...
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 ...
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 ...
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,$3E,$...
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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 ...
37
votes
4answers
15k views

Commodore 64 to modern TV

I've been thinking about getting a Commodore 64 machine. However, I realise there's obviously no video cables I have that will work. But when I looked online there are many people using S-Video to VGA ...
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 ...
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 ; &...
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
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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 ...
17
votes
4answers
1k views

Emulate smooth scrolling

One thing I really liked about the 8-bit (and even most 16-bit) games was that the frame rate was fixed to the vertical blanking. Games were smooth back then. I've been trying to recreate that feeling ...
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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 ...
15
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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 ...
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 ...
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 (...
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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 ...
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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. ...