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Questions tagged [commodore-64]

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

20
votes
1answer
651 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 ...
37
votes
4answers
17k 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 ...
17
votes
1answer
1k views

How to check the C64 graphics mode used by Maniac Mansion

I have been investigating the MS-DOS port of the C64's Maniac Mansion game. The original MS-DOS port used the C64-specific character map to draw the various backgrounds in the game. I noticed that ...
10
votes
3answers
1k 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 ...
27
votes
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 ...
14
votes
3answers
998 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 ...
26
votes
3answers
1k views

What are the differences between a PAL and NTSC C64?

A lot of programs released for the Commodore 64 contained different software for the PAL or NTSC computer. Why did they have different versions of the hardware? Did the software have to be different ...
21
votes
3answers
2k views

How can I overclock my Commodore 64?

My Commodore 64 is running quite slow, and my friends want it to be faster, thus overclocking it. But no one knows exactly how to do that. With our current "modern" stuff, nothing seems to help my ...
17
votes
1answer
669 views

How to move sprites to the border on c64?

As far as I know, there is no register in the VIC-II, which would enable this. Despite that, in nearly all intros and in many cases even in old games, sprites on the border were visible. Actually, it ...
17
votes
2answers
628 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 ...
13
votes
2answers
2k views

How does the Commodore 64 address more than 64 kilobytes of memory?

So, the Commodore 64 has two special registers in locations $00 and $01. By writing to these registers, you can somehow turn on and off the ROMs and other things. The thing that I am not understanding ...
12
votes
1answer
512 views

Why was the audio output of the SID6581 so variable between chips?

Each of the SID6581s I have tested sound different, particularly when it comes to filter cutoffs and distortion. What are the causes of these variances?
14
votes
2answers
1k views

What is the “standard” way to implement KERNAL hooks on the C64?

The C64 kernel (or KERNAL as it’s known in the C64 community) routines work via a jump vector table stored in page $03xx. A common programming paradigm to create something like a "device driver" would ...
13
votes
2answers
418 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. ...
12
votes
1answer
785 views

How to avoid sprites confusing the raster timings on C64?

This relates to another question about moving sprites to the border. On my experience, sprites confuse the raster timings very badly. I found this especially problematic, if sprites were moved to the ...
9
votes
1answer
827 views

What is this extra lead in my monitor cable?

I have a breadbox Commodore 64 with a Commodore 1702 monitor. My monitor has three RCA-style inputs on the back: Audio (White) Luma (Yellow) Chroma (Red) I purchased a cable which claims to be an ...
5
votes
2answers
188 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 ...