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Questions tagged [commodore-64]

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

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14
votes
3answers
3k views

How do you recognize an early production model Commodore 64?

The Commodore 64 was the most popular single retro-computer produced, probably selling something like 15 million units. Clearly, the C64 is not "rare", but early revisions from 1982 are highly prized ...
3
votes
2answers
1k 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 ...
10
votes
2answers
673 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 ...
53
votes
2answers
11k 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 ...
11
votes
1answer
618 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 ...
10
votes
2answers
704 views

Why does this BASIC program keep restarting?

Here is a BASIC program for the Commodore 64, which should load the LIB file from the disk, and then stop. Yes? 5 PRINT "LOADING..." 10 LOAD "LIB",8,1 20 STOP the LIB file is 102 bytes long and is ...
7
votes
2answers
1k views

C64: Strange Behaviour on Control Port 1

I wrote this little Basic program to get Joystick input from Control Port 1. I know that this method is very strange and is better for keyboard input. 20 get a$ 30 if a$="" then 20 32 b=asc(a$) 33 ...
10
votes
1answer
2k 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 ...
3
votes
2answers
571 views

C64, basic v2, DATA strange behavior

I have the following code line: 0DATA"-+-+-" Here "\" and "/" are the ASC codes 205 and 206. I get a syntax error: ?SYNTAX ERROR IN 0 READY. As I can remember, there was same special in the ...
18
votes
3answers
2k 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 ...
12
votes
1answer
500 views

Sprites not rendering correctly before $2000

I am currently testing out some stuff in assembly with C64Studio and Vice and I noticed something with odd sprites. My code starts at $1000 and my sprites at $2000 but when I try to lower the first ...
3
votes
1answer
274 views

Which material was used for the 6502/6510/8500 MOSFETs?

I know that in the 80s, there was a shift from aluminum gate material to polycrystalline silicon. I wonder because the 6502 was released in 1975 and there were a lot of different implementations and ...
9
votes
4answers
1k views

What's a safe and easy way to desolder the CPU from C64?

I have probably broken my CPU by connecting 5 V from Arduino (500 mA) to the SENSE Pin of the Casette Port, So now I wonder what would be the safest way to desolder the processor? I have a cheap ...
10
votes
2answers
957 views

How many IEC devices can I connect to a C64 / C128?

I have two C64's, a C128, and as for drives: SD2IEC, 1541-U2, 1541-II and a 1581 - that makes for 4 devices. Looking at the drives, those only allow 4 device ID settings (8,9,10,11), but according to ...
21
votes
1answer
1k 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 ...
11
votes
1answer
2k views

Why do many JiffyDOS users install a toggle switch to disable it?

For those that don't know, JiffyDOS is a ROM replacement for a Commodore 64 (and 128, I believe) and its 1541 disk drive. This ROM replacement provides OS shortcuts, faster load times, etc. I've ...
31
votes
6answers
2k views

Dumping and archiving C64 disks

Doing spring cleaning with family, I found some old C64 disks. These are really old and no one knows what to do with them. Archiving or dumping them seems to be options but we are unsure how to do so ...
8
votes
1answer
508 views

Which memory management is easiest to program - CoCo 3 or C128/Apple //e? [closed]

As the 8-bit systems hit their peak in the mid-1980s, breaking the 64K barrier was all the rage. Commodore, Apple, Atari, and Tandy all shipped new 8-bit machines that came standard with 128K. Of ...
28
votes
3answers
3k 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 ...
15
votes
2answers
1k views

What were the 9 VAC pins used for on the Commodore 64 User Port?

I read that pins 10 and 11 are the 9V AC +/- pins on the Commodore 64 User Port. Pin 10 is the + phase while pin 11 is the - phase. I realize the User Port wasn't as versatile as the Expansion Port (...
39
votes
5answers
6k views

Why do programmable sound generators like SID include a noise generator?

In layman's terms, please explain the reason that all the popular PSG's used in 1980s computers and game consoles provided an additional channel to generate programmable "noise". How was this "noise" ...
12
votes
3answers
2k views

What is the name of the back arrow key on C64 keyboard?

What is the name of the back arrow key on top left corner of the C64 Keyboard? Is it escape or back? Also I don't recall using this key. What was the intended usage of it?
11
votes
2answers
804 views

Did the ZX Spectrum have more original titles than C64?

From casual reading, it seems as though many C64 titles were ported from the ZX Spectrum. Why was this the case? Was the ZX Spectrum more popular? Or easier to develop for?
16
votes
2answers
10k views

Install Commodore 64 on VirtualBox

I have installed MS-DOS, FreeDOS and Windows 98 in Oracle VirtualBox. I want to try Commodore 64. How do I install a Commodore 64 emulator in VirtualBox?
6
votes
1answer
396 views

Other than Ocean, what other famous loaders were there? [closed]

Many people are familiar with the awesome Ocean loaders from the 8-bit days. For those that are not, "loaders" are small programs that were usually artwork and music (sometimes games) that were ...
22
votes
3answers
4k views

How was digital sound playback achieved on the Commodore 64?

The Commodore 64 did not have any hardware dedicated to digital audio playback, so how were some games and songs able to achieve this on an unmodified and unextended Commodore 64? Did these ...
13
votes
0answers
433 views

Is there a simple BASIC program that demonstrates SID6581 distortion?

Many songs use a SID6581 design "flaw", distortion, as an effect. I tried experimenting with the filter and resonance registers, but was unable to reproduce the sound. What conditions are necessary ...
15
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 ...
8
votes
3answers
797 views

Advantages to installing a parallel port in a C1541-family drive other than speed

Are there any advantages to installing a parallel port in a C1541-family drive and using a parallel cable to a PC to image disks, other than increased speed (i.e. since the standard IEC protocol is ...
10
votes
1answer
407 views

Is there any existing hardware mod for C64 to decouple tape drive from IEC (1581 drive collision)?

Commodore 64 has a known bug which doesn't allow to use tape drive together with a 1581 drive. Basically, in C64 the SRQ (Serial ReQuest) line is connected between IEC bus, CIA chip and the tape ...
9
votes
1answer
1k views

PAL C64 in the US - 50Hz vs 60Hz AC Frequency, will that matter?

I currently live in Japan and use PAL C64 from Europe, here the line voltage is 100V at 50Hz (Tokyo). I will be moving to the US in about 2 months. The US uses 110-120V (power supplies are usually ...
16
votes
1answer
610 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?
13
votes
1answer
1k 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 ...
18
votes
1answer
937 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 ...
10
votes
3answers
2k views

What Commodore 64 emulator and assembler to use? [closed]

I'm about to do some assembly coding for the C64 but for sanity I would like to do the actual coding on my Mac with an emulator. My question is; which is the most maintained/up-to-date emulator/...
14
votes
2answers
735 views

How can you tell if JiffyDOS is installed on a drive without opening it?

Is it possible (and if so, how) to tell if a drive has JiffyDOS installed without opening it and looking for the chip?
17
votes
1answer
2k views

How did the Epyx Fast Load cart work with a Commdore 64?

Why would adding a cart in your system suddenly speed up the C64 or the 1541 for loading games?
11
votes
1answer
415 views

Differences in disk storage between systems

Coming from the TRS-80/TandyColor Computer lines, I had always heard of how slow some other systems disk storage were, regarding data transfer rates, etc... The CoCo lines disk storage was pretty fast ...
8
votes
1answer
861 views

Commodore 64 with partly working keyboard

My Commodore 64 has developed a fault with the keyboard. Some of the keys are working and some aren't. As far as I can see there is no pattern and they are randomly distributed across the keyboard. ...
11
votes
1answer
550 views

How many analogue RGB signal levels did the VIC-II have?

Although only 16 different colors were allowed on c64 (more exactly, in the VIC-II), which came from a fixed palette, the video output created an analogoue tv signal. Which means, somewhere in the ...

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