Commodore 64 — The Machine with Three Voices

01 · THE MACHINEThe hardware — what was inside

The Commodore 64 was shown at the CES exhibition in Las Vegas on 7–10 January 1982 and went on the market in August 1982 for $595 [3][4]. The name comes from the memory: 64 KB of RAM. Jack Tramiel insisted on exactly that, even though 64-kilobit memory chips then cost over $100 each — he was counting on their price falling fast [4].

The working start-up is legendary: you switch on and within seconds you see the blue screen, 64K RAM SYSTEM 38911 BASIC BYTES FREE and READY. — BASIC is in ROM and does not wait for a disk [4].

02 · SIDThe sound chip — the heart of the C64

The SID chip was designed by Bob Yannes with a small team — it was ready in five months in the second half of 1981 [5]. Yannes later co-founded the synthesiser maker Ensoniq. His goal was a real instrument, not squeaks and screeches:

“…primitive and obviously had been designed by people who knew nothing about music.”

(on the sound chips on the market)

Bob Yannes, in Brian Bagnall, “On the Edge” (2006) — quoted after [5]

What the SID can do [2][5]:

• 3 independent voices, each with a triangle, sawtooth or pulse waveform, or noise.
• An ADSR envelope for each voice — how the sound rises, decays and fades, as with a real instrument.
• An analogue filter with low-pass, high-pass and band-pass modes (a notch is obtained by combining them).
• Ring modulation and synchronisation between voices — a metallic, bell-like timbre.
• Pulse-width modulation — a “breathing” sound.

Try it yourself — a BASIC program that plays a note (the registers start at $D400, i.e. 54272 [1]):

10 REM  SID: 1 voice, triangle waveform, a note around A (440 Hz)
20 POKE 54296,15      : REM maximum volume
30 POKE 54277,9       : REM attack 0, decay 9
40 POKE 54278,240     : REM sustain 15, release 0
50 POKE 54273,28      : REM frequency, high byte
60 POKE 54272,160     : REM frequency, low byte (28*256+160 = 7328)
70 POKE 54276,17      : REM voice 1: gate + triangle waveform
80 FOR I=1 TO 500: NEXT I
90 POKE 54276,16      : REM gate off — the note fades

The value 7328 gives about 430 Hz on PAL and about 447 Hz on NTSC machines — close to the A of the first octave [1][2].

03 · THE GAMESThe games — about 10,000 titles

Roughly 10,000 commercial programs were made for the C64 — games, tools and office software [4]. A few worth knowing:

04 · THE MUSICIANSThe composers — artists with code

The C64 created a new craft: music written as a program. The best-known names and titles, according to the reference work on the chip [5]:

The people who wrote them describe the SID as a musical instrument in its own right [5]. If you want to hear how it sounded — the HVSC (High Voltage SID Collection) archive, started in 1996 (version 1.0 with 4,079 files), now collects nearly 60,000 tunes, played by an emulator or by a real chip [15].

05 · THE DEMOSCENEThe demoscene — art under constraints

The demoscene was born in the 8-bit era, on machines such as the C64, ZX Spectrum and Amstrad CPC. At first crackers put a short graphical intro (a cracktro) in front of copied games; over time programmers began writing them just to show what they could do — and that became the demo [13]. The C64 is regarded as the machine that did most to popularise the scene [4].

A typical C64 demo combines:

• scrolling text and coloured bars (raster bars);
• more than 8 sprites at once (sprite multiplexing);
• music synchronised with the picture;
• 3D objects and plasma effects in real time;
• a list of “greetings” to other groups.

Well-known groups include Fairlight, Triad, Crest, Oxyron, Censor Design and Booze Design — a detailed list is in the CSDb database (csdb.dk).

The secret is the raster interrupt: the VIC-II draws the screen line by line, and the programmer can catch a specific line and change a colour, a sprite position or a sound register. A minimal assembly example — it changes the border colour on a given line:

        SEI                 ; disable interrupts
        LDA #$7F
        STA $DC0D           ; switch off the CIA timer interrupt
        LDA #<isr
        STA $0314           ; IRQ vector — low byte
        LDA #>isr
        STA $0315           ; IRQ vector — high byte
        LDA #100
        STA $D012           ; we want an interrupt at raster line 100
        LDA $D011
        AND #$7F
        STA $D011           ; the highest bit of the line number = 0
        LDA #$01
        STA $D01A           ; enable the raster interrupt
        CLI                 ; enable interrupts
loop    JMP loop            ; the main program simply waits

isr     INC $D020           ; change the border colour
        ASL $D019           ; acknowledge the VIC-II interrupt
        JMP $EA31           ; continue the system's normal handling

06 · BASICBASIC V2 — a great computer, a modest language

The built-in Commodore BASIC 2.0 is the same as in the VIC-20 [4]. It had no commands for sprites and sound — BYTE magazine criticised it in 1983 because everything had to be done with POKE [4]. That is why many people bought the Simons' BASIC extension — 114 additional commands written by the then 16-year-old David Simons [14] — or learned assembly.

Here is how to display a sprite in plain BASIC. First we give it a shape (a solid block), then we move it:

10 REM  sprite shape: a solid block of 63 bytes at address 832
20 FOR I=0 TO 62: POKE 832+I,255: NEXT I
30 POKE 2040,13      : REM sprite 0 takes its data from block 13 (13*64=832)
40 POKE 53269,1      : REM switch on sprite 0
50 POKE 53287,7      : REM colour of sprite 0 = yellow
60 POKE 53249,100    : REM Y position
70 FOR X=24 TO 320
80 POKE 53248,X AND 255          : REM X position, low byte
90 IF X>255 THEN POKE 53264,1 ELSE POKE 53264,0 : REM 9th bit of X
100 NEXT X

07 · THE LEGACYWhat remains today

• The music: Elektron's SidStation synthesiser (1997) is built around a real 6581 chip [5].
• The games: SCUMM, born with Maniac Mansion, led to LucasArts' adventures [7].
• The enthusiasts: the C64 is still used by enthusiasts, and emulators run its programs on a modern computer [4].
• New hardware: the Commodore 64 Ultimate (2025) — an FPGA replica with HDMI, Wi-Fi and USB, billed as “at least 99% compatible”. Three editions: BASIC Beige — $299, Starlight — $349.99, Founders — $499.99. When it was announced (July 2025), delivery was planned for October–November 2025 [16].

A nostalgic overview article. Prices are historical, in the original currency. Checked on 3 October 2026.

08 · SOURCESSources

1. Commodore 64 Programmer's Reference Guide, Commodore Business Machines, 1982 — classiccmp.org (PDF)
2. MOS 6581 Sound Interface Device (SID) — specification, Commodore Semiconductor Group, October 1982 — archive.6502.org (PDF)
3. T. S. Perry, P. Wallich, “Design case history: the Commodore 64”, IEEE Spectrum, March 1985 — doi.org/10.1109/MSPEC.1985.6370590
4. Wikipedia, “Commodore 64” (secondary: sales, prices, specification, BYTE 1983) — en.wikipedia.org/wiki/Commodore_64
5. Wikipedia, “MOS Technology 6581” (secondary: SID, versions, composers) — en.wikipedia.org/wiki/MOS_Technology_6581
6. Wikipedia, “Boulder Dash (video game)” — en.wikipedia.org
7. Wikipedia, “Maniac Mansion” — en.wikipedia.org/wiki/Maniac_Mansion
8. Wikipedia, “Elite (video game)” — en.wikipedia.org
9. Wikipedia, “Impossible Mission” — en.wikipedia.org/wiki/Impossible_Mission
10. Wikipedia, “SimCity (1989 video game)” — en.wikipedia.org
11. Wikipedia, “Little Computer People” — en.wikipedia.org
12. Wikipedia, “Katakis” — en.wikipedia.org/wiki/Katakis
13. Wikipedia, “Cracktro” (origin of the demoscene) — en.wikipedia.org/wiki/Cracktro
14. Creative Computing, November 1983, “Simons' BASIC” — atarimagazines.com
15. High Voltage SID Collection — hvsc.c64.org · milestones: remix64.com
16. Time Extension, “Commodore's New Ownership Unveils The Commodore 64 Ultimate”, July 2025 (secondary) — timeextension.com

Checked on 3 October 2026. Primary sources [1]–[3] are cited for the specifications; the sales figures, prices, games and dates were checked against the reference works [4]–[16]. Not checked individually: the 1541 disk capacity (about 170 KB) and the sprite size (24×21 pixels) — taken from reference [1].

09 · RELATEDContinue from here

Opinions and personal memories of the machines are at galin.kagami.bg.