Questions tagged [commodore-64]
For questions about the different versions and products of the Commodore 64
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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 ...
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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
...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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.
...
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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 $...
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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 ...
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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 ...
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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 ...
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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 ...
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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?
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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 ...
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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 ...
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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 ...
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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:
* ...
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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 ...
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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 ...
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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 ...
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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 ...
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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
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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 ...
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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 ...
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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 ...
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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
...
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How does the C64 get an accurate TOD clock on both 60 Hz and 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 ...
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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 ...
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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'...
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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 ...
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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 ...
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Oxford C compiler for Commodore 64
I kept one floppy from my Commodore 128 (which I used mostly in C64 mode), labelled ‘Oxford C compiler’. It is a 5.25″ floppy. Don't ask me why I kept just this one; probably because I thought I ...
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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 ...
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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 ...
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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 ...
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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
...
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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 ...
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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?
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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 ...
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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 ...
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Origin of VIC-II (PAL) chip labelled 8656R2?
Wondering why a C64 VIC chip (fully functional) that I got off eBay had an 8565R2 label fitted on top of it:
I peeled it off to find this:
I haven't ever heard of a VIC-II (PAL) labelled MOS 8656R2. ...
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Commercial C64 software implemented in Forth?
There has been several implementations of Forth that were running on, and targeting, the C64. Were there any commercial software releases (not throw-away hobby projects or in-house utilities) that ...
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How to write directly to the Commodore 64 (or similar) DAC [duplicate]
I read some related information in a SAM question but I want to know exactly how to write amplitudes directly to the DAC, sample by sample, like in a bytebeat formula. I understand it is possible on ...
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Did any devices use the Commodore 64 joystick ports as outputs or two-way communications ports?
Looking at the schematic and explanation of how the C64 joystick
ports work, it seems clear that the stick direction and button
lines (JOYA0, through JOYA3 for port 1 and JOYB0, through
JOYB3 for port ...
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How is PETSCII used by assembly-language programs?
First, a bit of context. I wrote an
interactive disassembler for 6502 code that,
among other things, attempts to identify ASCII strings automatically.
Appropriate source code for different assemblers ...
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How did the Sinclair compare on price with the C64 in the UK?
As far as I know, the popular low-end home computers in the UK around the mid-1980s were the Sinclair ZX-Spectrum ("Speccy") and the Commodore C64. I know the BBC micro also had a following, but my ...
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How did C64 games handle music during gameplay?
On the C64 there was no threading, so how did games handle treating at the same time music and game code? Music requires exact timings, and the SID had to be instructed to change the note at the right ...
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Understanding C64 Character Memory
I'm trying to understand how video memory worked on the Commodore64 in text mode. I see that the VIC-II has a memory setup register (at $D018) that keeps track of some of this information along with ...
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Pac-Man-like: Playing a Excavator bucket or mining drill on a cable
I remember playing this game on the C=64 in the late 80s or so.
It was 2d 'platformer' arcade game where you have to clean the screen from pills like Pac-Man, but in a different way. You would always ...
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