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Questions tagged [vic-20]

For questions about the Commodore VIC-20

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Did the Vic-20 save money using static RAM?

The unexpanded Vic-20 had 5K of RAM. This was quite small even by 1981 standards, but it was trying to be cheap enough for consumers to buy, and it succeeded, selling over 2 million units. One reason ...
rwallace's user avatar
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5 votes
1 answer
401 views

Why does the VIC-20 have its cartridge area at a higher adress than the I/O area?

Why did the designers of the Commodore VIC-20 chose to put the main cartridge ROM area at $A000, beyond the character ROM area at $8000 and the I/O area at $9000? Flipping the two around, with the ROM ...
TeaRex's user avatar
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15 votes
2 answers
3k views

Were cartridge slots cheaper at the back?

I'm remembering a difference in the design of Commodore computers like the Vic and 64, versus the Atari 8-bits, and game consoles from the likes of Atari and Nintendo: they all had cartridge slots, ...
rwallace's user avatar
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6 votes
0 answers
241 views

What were VIC-20 year-by-year sales?

From "Commodore VIC-20: Worlds First Computer to Sell 1 Million Units" I see that: Between early 1981, when the VIC actually hit store shelves, and the first few months of 1985, when the ...
cjs's user avatar
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23 votes
8 answers
4k views

Why did the VIC-20 and C64 have only 22 and 40 columns when the earlier PET had 80 column text?

When I was a kid, the "real" computers in movies looked so cool with that 80-column monochrome green text. My first computer was a VIC-20 and it always felt very "toy-like" to me ...
AvaTaylor's user avatar
  • 465
16 votes
3 answers
2k views

VIC20, VIC-20, or VIC 20?

The 'tag' on this website calls it 'VIC-20', but the VIC20 user manual (Personal Computing on the VIC20) http://cini.classiccmp.org/pdf/Commodore/VIC-20%20User's%20Manual.pdf calls the VIC either ...
TopCat's user avatar
  • 260
7 votes
3 answers
713 views

Why did the Vic-20 need special chips for I/O?

The Vic-20 used two 6522 VIA chips for I/O. I asked why it had two of them but thanks to a comment from Bruce Abbott, I now think that wasn't quite the question I needed to ask. What I really need to ...
rwallace's user avatar
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6 votes
1 answer
1k views

Why does the Vic-20 have two VIA chips?

The Vic-20 uses the 6522 VIA for peripheral I/O. However, it has two of them. I find this surprising, particularly considering minimizing cost was an important design goal. Is there a reason why it ...
rwallace's user avatar
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4 votes
1 answer
338 views

From what errors could Commodore's tape loader recover

The Commodore PET/VIC-20/C64 tape routines write out the leader for each file twice, and then write the data twice. While it would seem that this should allow data to be loaded more reliably, ...
supercat's user avatar
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5 votes
1 answer
305 views

Upping the speed of the VIC-20 tape drive: aftermarket hardware for the expansion port with "rabbit" in the name?

EDIT: I realize from reading the comments that I was bit loose in my use of the word "speed" as a property of the tape drive. What I had in mind was the speed of the data transfer, not the ...
user19267's user avatar
14 votes
3 answers
1k views

VIC-20 vs. VC20 (or VC-20)

My first computer was a VC20. Was it just renamed (for the German market?) as a VolksComputer? (I am a Finn and the VC was bought in Finland). Or were there any actual differences to VIC-20?
Tuomo's user avatar
  • 327
3 votes
0 answers
162 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 ...
supercat's user avatar
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2 votes
1 answer
225 views

Vic-20 tape I/O dependence on CPU speed?

As I understand it, the Vic-20 reads and writes the cassette deck by the low-tech expedient of just using the CPU to bit-bang a one-bit serial line. This presumably means that for a given code ...
rwallace's user avatar
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11 votes
1 answer
1k views

cprintf printing invisible characters in C program on VIC 20

I want to compile and run a Hello World program in C with the cc65 compiler for an unexpanded VIC-20 model. For printing I'm using the conio.h function cprintf, since the conio implementation requires ...
Peter B.'s user avatar
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7 votes
3 answers
647 views

How do I adjust the OS print output to different screen dimensions on VIC-20?

The graphics chip of the VIC-20 has a setting for the number of columns and the number of rows to display. So, instead of the default values of 22 columns and 23 rows, for example, it is possible to ...
Peter B.'s user avatar
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3 votes
1 answer
317 views

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 ...
Gabriel Vinazza's user avatar
10 votes
4 answers
1k views

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 ...
cjs's user avatar
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4 votes
1 answer
839 views

Was there any VIC-20 expansion to bring memory beyond the default maximum of 40 KiB?

The Commodore 64 was very flexible in terms of how RAM could be controlled. ROMs and I/O devices could easily be swapped out by setting bits in the first two addresses of memory. The VIC-20's ROMs and ...
Serentty's user avatar
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5 votes
0 answers
176 views

Vic-20 total game cartridge sales

The Vic-20, like many home computers of its time, had a cartridge slot that could be used both as a general expansion slot, and for game cartridges like a console. Game cartridges on the Commodore ...
rwallace's user avatar
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5 votes
4 answers
3k views

How does memory addressing/mapping work in 8-bit systems?

If I attach a 16 KIB EEPROM to a 6502 or similar, and put some kind of operating system on it, it will run fine, but won't have access to any other chips. So, when a Commodore VIC20 had 5k of ram and ...
user10868's user avatar
6 votes
4 answers
1k views

Cartridge modems - was the Vic-20 a special case?

'The Home Computer Wars' has this to say about the development of the cartridge modem for the Vic-20: The size of the case was another problem. Most modems came in bulky rectangular boxes about 10 ...
rwallace's user avatar
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5 votes
1 answer
418 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,$3E,$...
jpcohet's user avatar
  • 51
8 votes
2 answers
1k 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 $...
wizofwor's user avatar
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24 votes
2 answers
4k views

Why does the VIC-20 have 5KiB of RAM?

Why does the VIC-20 have 5 KiB of RAM? Why not a multiple of 4 as any other systems, e.g 4 KiB or 8 KiB. Is there a technical reason for that?
Biff Iam's user avatar
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10 votes
3 answers
1k views

Commodore VIC-20/64/128/16/Plus 4 floppy disk drive replacement

We all know that floppy disks are getting hard to find, and floppy drives are fragile to begin with (especially Commodore's 1541 drive). I know that several companies and parties have released floppy ...
Jim MacKenzie's user avatar
8 votes
3 answers
3k views

Getting your Commodore VIC-20, 64 or 128 online

Back in the day, of course we used modems ("dial-up modems" in today's parlance) to get our Commodores connected to other systems. These days I know several people have concocted options to get ...
Jim MacKenzie's user avatar
34 votes
3 answers
2k 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 ...
Psychonaut's user avatar
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18 votes
6 answers
1k views

Is there software that will run across multiple Commodore 8-bit machines without modification?

I noticed in some of the answers in this question that the Commodore 8-bit line apparently used a jump table at $03xx for entry into the kernel ("kernal" for the pedantic) routines. Figuring that the ...
bjb's user avatar
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9 votes
1 answer
1k views

What was the difference between "Video Low" and "Video High" on the VIC-20?

I was reading about the Audio/Video port pinouts of the VIC-20 and I noticed that pin 4 is VID L and pin 5 is VID H meaning Video Low and Video High, respectively. I'm familiar with luma, chroma, etc....
cbmeeks's user avatar
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10 votes
2 answers
2k views

Did the VIC-20 support raster scanline tricks like the Commodore 64?

I've been programming the C64 on/off for over 30 years (wow). However, I have a few VIC-20's I want to program. I never had a VIC-20 as a kid so I haven't had much exposure to them. Am I correct in ...
cbmeeks's user avatar
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11 votes
2 answers
616 views

Where to find thermal paper for Aquarius or Commodore printer?

The thermal printer that was sold for use with the Mattel Aquarius or VIC-20 / Commodore 64 is an Alphacom VP42. This uses thermal paper, 4⅜″ wide. Original paper for these printers is very hard to ...
Cees Meijer's user avatar
20 votes
2 answers
848 views

What was the end of line convention for text files on the 8-bit Commodores

A two part question: Did an agreed upon convention for end of line (EOL) within text files exist on the 8-bit Commodores? If there was a convention, what was it?
Shannon Severance's user avatar