Questions tagged [commodore-64]

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

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3
votes
2answers
128 views

Printing German umlauts with cc65

I want to print German texts with umlauts with a compiled C program on the C64. I'm aware that these characters are not in the charset and that I will have to change the character set. However, it ...
16
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2answers
2k views

Is there a Commodore 64 emulator that can profile running code?

I am developing some software for the Commodore 64, and I am concerned about its runspeed. Is there an emulator that can report, after running my code, where exactly it spent most of its time? I'm ...
4
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3answers
872 views

What are D64, T64, D71 and D81 files?

The docs for the Ultimate-II+ expansion cartridge for the Commodore 64 state: It is able to read D64 files, as well as D71 and D81 files (no partitions), T64 files. So what are D64, T64, D71 and ...
14
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2answers
3k views

How do C64 cartridges swap running programs without losing state and context?

I recently picked up a 1541 Ultimate II+ for my Commodore 64 and have been amazed at how this device seemingly can do every flash memory and other enhancement feature for the machine, short of CPU ...
2
votes
1answer
119 views

What is the file that VICE refers to as dos1541?

VICE needs a file called dos1541 if you want hardware emulation of the 1541 disk drive. What does that file contain, exactly? The 1541 seems to have two ROMs: a DOS and a KERNAL. But if I take the ...
3
votes
1answer
77 views

How to pass a value to an inline assembler script in a #define macro in cc65

I'm trying to add a compact #define macro in a cc65 program for performing various low-level tasks efficiently. For some of the macros, I need to pass a non-constant value to the assembler part. I ...
3
votes
1answer
167 views

Commodore 64 board dimensions

What are the dimensions of the C64 motherboard? I am specifically asking this because I am considering using a 64C case (these still seem to be in production) for an 8-bit homebrew machine. I wonder ...
1
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0answers
143 views

Thinking through the design of a TTL video card: what memory chips and how to manage memory? [closed]

Inspired by Ben Eater's "Let's build a video card" aka "World's worst video card" two part projects on YouTube, I was inspired to consider designing a display adapter for my passive backplane TTL mini-...
0
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0answers
65 views

Composite video from C64 not being picked up by a modern Smart TV [duplicate]

I've purchased a Commodore 64 "as-is" from eBay. I tediously cleaned out the interior and removed all chips and dusted them out and put them back together. Still, no signal. Except for sound. So, I ...
1
vote
1answer
161 views

How can I link a BASIC program with BASIC 3.5 for C64?

In the magazine 64er from June 1990 a BASIC extension for running Commodore Basic V3.5 on the C64 was presented. The extension is available at csdb. However, to run a BASIC 3.5 program, it is ...
10
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1answer
751 views

Why did the C64 use a separate “CAN” +5 V power supply for some chips?

The Commodore 64 had two separate +5 V power supplies: one supplied by the external PSU brick and a second one generated on-board from the 9 VAC via a 7805 regulator. This second +5 V power supply was ...
23
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3answers
4k views

Could you manually eject a floppy quick enough to prevent data loss?

I have the vague recollection of "Panic Ejecting" floppy disks by lifting the latch on the drive after immediately regretting a command I had typed. At the time, I was young, impulsive, and blessed ...
12
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2answers
287 views

Was the Commodore 128 movable zero page / stack and second block of color RAM actually used?

The Commodore 128 hardware allowed two things that weren't possible on the C64: Moving the 6502 zero page and 6502 stack to another place in RAM besides pages 0 and 1, and switching the CPU and/or the ...
7
votes
2answers
725 views

What does Shift-RETURN do on Commodore's 8-bit computers?

Someone recently commented that, "a shift-Return is really different from a normal one. It moves the cursor to the next line, but does not complete an input operation." This would be interesting and ...
13
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2answers
3k views

How did I fry my SID chip?

I recently got a SID chip (8580r5) for $35 and got it playing music. I was really happy about it. I hooked up a small amp chip to the 9V supply momentarily (it didn't work, I was building that part of ...
8
votes
3answers
609 views

What are my options for fast bidirectional transfer between a C64 and a 1541?

Since asking a similar question, which is really exclusively about using KERNAL to transfer between disk drive and computer, comments, answers and others hint at the fact that using the KERNAL really ...
10
votes
1answer
1k views

How fast are transfers between the C64 and the 1541 floppy drive?

I am developing some software for the Commodore 64, and my intention is to use the 1541 as a coprocessor. I'll have the 1541 compute some data for me, and then retrieve this data over the serial line. ...
14
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2answers
2k views

How was a line of Commodore 64 BASIC code stored in its memory?

I am reading up on old C64 stuff and I am using the Vice emulator to play with it. Currently I am studying about how the C64 stored BASIC programs in RAM. This is quite clear (it starts on address $...
18
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3answers
4k views

Are pixels on the Commodore 64 square?

Are "tile pixels" the same size as "sprite pixels", and are they both square (ignoring the rule that multicolor sprites can only be colored in groups of two pixels)? By "square" I mean that the ...
3
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0answers
97 views

Commodore tape drive performance specs

Over the years during which Commodore sold tape drives, there have been a few different versions of the drive with different analog electronics. I'm interested in experimenting with "turbo" tape ...
8
votes
4answers
593 views

How do you play “The Sentinel”?

Many, many years ago, we had a game for the Commodore 64 called "The Sentinel". I remember reading the instructions and being utterly baffled as to how you actually play the damned thing! Hopefully ...
3
votes
1answer
225 views

The Sentinel (aka The Sentry) on Commodore 64 - why was scrolling so fast?

On the Commodore 64 3D games which use one of the bitmap screen modes were notoriously slow. However watching a gameplay video of The Sentinel will show that in the first-person view, looking around ...
4
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1answer
232 views

What is the largest RAM expansion for Amiga or Commodore? [closed]

What is the largest RAM expansion being manufactured today for Amiga and Commodore 8-bit?
5
votes
4answers
850 views

Is it possible in Commodore BASIC V2.0 to configure the system so that the PRINT command does not update color?

The PRINTcommand in Commodore BASIC V2.0 (the one that runs on the Commodore 64) prints each character to the screen address (which is set by the byte in address 648) as well as putting the current ...
20
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5answers
6k views

Were the custom chips in the Amiga exploited for their hardware bugs like the ones in the C64 and Atari 8 bit computers were?

Here we are some decades on from the C64, and other 8 bit computers. New ideas that resulted in some new graphics effect or mode seem to happen, though we may be near the end of all that. Took a ...
10
votes
1answer
876 views

What sort of RAM chips did the Commodore 64 use in 1994?

For the first few years after its release in 1982, the Commodore 64 used eight RAM chips of 64kbit each. In the late eighties, it became cheaper to use a pair of 256kbit chips of the 4-bit-wide ...
4
votes
3answers
158 views

ca65 vs tass syntax: converting a hex address to decimal?

Most of the tass example programs start with a header like this, which places BASIC code at the beginning of the file that has an appropriate SYS instruction to run the rest of the application: * ...
5
votes
1answer
193 views

SID, sampled sound and bad lines

The SID could play sampled sound by poking a click into the chip at an appropriate frequency, and some Commodore 64 games like Ghostbusters and Impossible Mission did this (though only for a few ...
2
votes
1answer
170 views

What was the die size of the 6581 SID?

The MOS 6581 SID, the original version of the sound chip in the Commodore 64, was according to Wikipedia, 'produced in 7-micrometer technology to gain a high yield; the state of the art at the time ...
15
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1answer
1k views

Can I use all features of a Commodore 1571 external drive from a C64?

I know that the Commodore 1571 drive works perfectly well with a C64, since the 1571 will detect it is connected to a C64, and will enter 1541 emulation mode. After which, the 1571 just behaves as a ...
6
votes
1answer
267 views

Putting code into two different memory areas with cc65/ca65

According to cc65 / ca65 documentation, the .org directive does not affect the placement of the code unlike with other 6502 assemblers. The docs suggest defining a memory segment with the intended ...
5
votes
2answers
793 views

What sort of SBC is in the C64 Maxi?

Curious as to what model SBC this unit is using https://retrogames.biz/thec64 8 bit guys teardown says the internals are 'an ARM computer similar to a Raspberry Pi' https://youtu.be/kxx2F4ffmeE
4
votes
1answer
231 views

SID to WAV converter that exports per channel separately

For a C64 SID project of mine (https://soundcloud.com/c64er) I was using an converter almost 10 years ago, but it is missing now with its name... I researched many sites, but no lucky. Is there any ...
7
votes
1answer
377 views

What is the C64 disk drive “Jiffy” protocol?

There seems to be something called the "Jiffy protocol" used for some fast load systems. I know of the JiffyDOS product, which seems to require replacing ROMs in both the C64 and the drive, but it ...
8
votes
3answers
577 views

Are there any open-source C64 DOS wedges and fast loaders?

The ever-so-popular EPYX Fast Load cartridge for the Commodore 64 included a DOS wedge (adding commands such as $ to list the files on a disk, /filename to load a file and @ to show the disk error ...
9
votes
1answer
313 views

What is the exact bus protocol used by the C64/C128 REU?

The Commodore 64/128 RAM Expansion Units used a DMA controller to move data between the REU's RAM and system RAM (or I/O space). One would set the addreses, length and direction for the transfer (or ...
19
votes
1answer
1k views

How does the C64 get an accurate TOD clock on 50 Hz power?

The C64 has two Time of Day (TOD) clocks, one in each of its 6526 CIA chips U1 and U2. These calculate time based on a 60 Hz or 50 Hz input to the TOD pin (pin 19); the clock input frequency assumed ...
7
votes
2answers
425 views

Get exact position of raster beam on C64/C128

By reading register $D012/$D011 or when pausing the execution of an emulation in VICE starting the monitor and entering io d000, it is possible to get information about the current rasterline. For ...
6
votes
2answers
489 views

Commodore monitor to VGA or HDMI

I have this monitor, which I think is a Commodore 64 monitor. I would like to connect it to a pc. Anyone know how to convert VGA or HDMI to this connector format? I've tried searching, but so far I'...
5
votes
1answer
282 views

Adding control characters to string constants in ca65 assembler

According to the cc65 documentation, a string constant in assembler programs can be defined with the .ASCIIZ command. However, I could not manage to sneak control commands in, for example, the ...
6
votes
1answer
199 views

Different handling of ASCII interpretation between ca65 and cl65

I stumbled upon a divergence in the ASCII upper case/lower case handling when using assembler and linker of the cc65 suite separately (I used cc65 V2.15 on Win10). For a test I made the following ...
13
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0answers
441 views

Oxford C compiler for Commodore 64

I kept one floppy from my Commodore 128 (which I used mostly in C64 mode), which is written Oxford C compiler. It is a 5.25" floppy. Don't ask me why I kept just this one; probably because I thought I ...
9
votes
4answers
629 views

Which cartridges were typically used together on Commodore 64 systems?

It's possible to extend the Commodore 64 expansion port bus with boards like the [Aprospand-64]: This example dates from 1986, but there appear to have been a number of contemporary expanders, and ...
4
votes
1answer
661 views

How did “RAM” cartridges for the C64 work?

Section 7.1.1.2 of the VICE manual mentions that cartridge slot 1 (of the four slots 0, 1, Main and I/O) in the emulator is special in that it's designed to support "mostly RAM-based cartridges" (of ...
15
votes
1answer
636 views

Under what circumstances would RAM locations 0 and 1 be written and/or read on the C64?

To be clear, I'm talking about the actual memory cells at addresses $0000 and $0001 in the DRAM chips. Devices can of course initiate read or write requests to these address on the address/data buses ...
7
votes
1answer
721 views

Could the Commodore 64 have used the 6522 VIA instead of the 6526 CIA?

The VIC-20 used a 6522 VIA chip with a couple of 8-bit PIO ports, a couple of timers and a (buggy) shift register. (The bug in the shift register could be worked around with external hardware or in ...
7
votes
2answers
380 views

Is it safe for C64 cartridges to respond to read and/or write requests on “unmapped” addresses?

According to the C64 wiki, asserting G̅A̅M̅E̅ on the cartridge port (and not asserting E̅X̅R̅O̅M̅) of the C64 leaves three blocks of the C64 address space "unmapped": 28 KB @ $1000 (otherwise RAM), 8 ...
1
vote
0answers
99 views

What cable do I need to connect my old commodore64 with a tv (as monitor) [duplicate]

I want to use an old commodore64. In the 80s we connected a small tv, as a monitor, but the cable for that connection is missing. What kind of cable connection do I need?
35
votes
3answers
3k views

Why did the VIC-II and SID use 6 µm technology in the era of 3 µm and 1.5 µm?

In short, 3 µm looks like it was the "standard" process size at the time, and it was available to Commodore before the chips were designed. Therefore it looks like using the larger 5 to 7 µm process ...
11
votes
3answers
484 views

Commodore 64 with partly working keyboard (part 2)

I have a C64 that has recently stopped responding to two 'columns' of keys, namely '9,0' 'i,o' 'j,k' and 'n,m' - I've swapped the CIA chips (U1 and U2) to no effect, so I pulled a keyboard from a ...