The commodore CBM 620 is the same machine as the CBM 610, but with more memory, 256KByte instead of the 128KByte of the 610. It is functionally the same as the CBM 720 computer, but with an 8x8 pixel character ROM, as opposed to the 8x14 pixel characters of the 720. The case is the same as that of the CBM 500 series.

The Commodore 600 series was introduced in 1982 and sold in the US as the B128 / B256 and in Europe as the the CBM 600 series. The B128/600 series are in an identical case as the B500 series but have the MOS 6509A CPU running at 2MHz. The VID-II video chip was not used for this series, since it targeted the business market. Instead, the 6545 CRT Controller was used so that 80 columns could be displayed.

The following configurations were sold:

• CBM 610 (B128) - 128KByte RAM
• CBM 620 (B256) - 256KByte RAM
• CBM 630 (B256) - 256KByte RAM + CoProcessor board

The 600 series uses the 6509A CPU clocked at 2MHz and has 40KByte ROM with BASIC 4.0. An additional 704KByte of external RAM is supported through bank switching. Some of the other capabilities and peripherals were:

• MOS 6551 ACIA chip with an RS232-C port
• IEEE-488 compatible peripheral port
• MOS 6581 SID for sound
• MOS 6525 TriPort Interface (TPI) Chip for the keyboard
• MOS 6545 CRT Controller for 80x25 monochrome text**

** Graphics were limited to 80x25 characters with a 8x8 character matrix

The CBM-II has two incarnations, the P series (P = personal, or, home use) and the B series (B = business use). The B series was available with a built-in monochrome monitor with detached keyboard (hi-profile) but also available as a single unit with built-in keyboard but no monitor (lo-profile). These machines are often referred to as the "Porsche PETs" due to incorrect rumors that the case was designed by Porsche. Though Commodore did initially consult Porsche for a case design, it proved too expensive to produce, so Commodore enlisted designer Ira Velinski to create one based on the original PET prototype

The Commodore PET line began in 1977 with the PET 2001, one of the earliest all-in-one personal computers. It featured a MOS Technology 6502 CPU running at 1 MHz, with 4–8 KB of RAM (expandable to 32 KB in later revisions), and a built-in monochrome monitor and cassette drive. The machine used a character-based display with a 40×25 screen buffer mapped directly into memory, and graphics were limited to PETSCII, a modified ASCII set with block-drawing symbols. Its BASIC interpreter, written by Microsoft, was in ROM, ensuring instant-on usability. The PET 2001 established the architecture that would define the series: a 6502 processor, memory-mapped I/O, BASIC in ROM, and integrated display and keyboard.

The PET branding was used primarily in North America and early European Sales. Later the CBM (Commodore Business Machines) branding was applied more heavily in Europe, as PET had trademark conflicts with the Dutch Philips company, which used PET for a line of audio products.

Later models, such as the 3000 and 4000 series, refined this architecture. They introduced larger memory configurations, replacing the original "chiclet" keyboard with full-travel designs, and replacing the built-in cassette with external storage options. The 4000 series added an 80-column text mode in some variants, using additional video RAM and CRT controllers. While the core 6502 CPU and BASIC ROM remained consistent, the bus architecture was gradually expanded to support more RAM (up to 96 KB, though not all was directly addressable by BASIC). These systems also introduced IEEE-488 (GPIB) ports for disk drives and printers, a notable departure from the hobbyist S-100 or RS-232 setups common in other machines of the era.

The final iteration, the 8000 series (sometimes called “Big PETs”), pushed the PET architecture to its practical limits. With up to 96 KB of RAM and a full 80×25 display standard, these machines were targeted toward business and scientific use rather than hobbyists. They retained the 6502 core and Microsoft BASIC ROMs but added more advanced video circuitry and professional keyboard layouts. Despite their improvements, the PET line was eventually eclipsed by the Commodore 64 and the CBM-II series, which offered richer graphics and sound. Still, the PET series represents a coherent lineage: a consistent 6502-based core with incremental refinements in display, memory, and I/O, bridging the gap between early hobbyist machines and professional microcomputers.

The PET/CBM line was tightly coupled with a family of IEEE-488 (GPIB) peripherals, which gave these machines a more professional edge compared to contemporaries that relied on hobbyist interfaces. Commodore produced a range of disk drives, starting with the 2040 dual floppy (based on 5.25-inch drives with ~170 KB per side), followed by the improved 4040, 8050, and 8250 drives that expanded capacity up to over 1 MB per disk with double-sided, double-density mechanisms. All of these were “intelligent” peripherals, containing their own 6502 processors and DOS in ROM, so the PET simply issued high-level commands over the IEEE-488 bus. Printers were also available, such as the CBM 2022 and 3022 dot-matrix units, which were business-grade and designed to work seamlessly with PETSCII character encoding and Commodore’s control codes.

Beyond mass storage and printers, Commodore offered a number of specialized peripherals for the PET/CBM ecosystem. The 2020 and 3020 were daisy-wheel and line printers, respectively, catering to office needs. Tape drives like the C2N datasette remained supported for low-cost storage and software distribution, though serious users quickly moved to IEEE-488 disks. Plotters, like the 4016, extended the system into technical and educational applications, and even third-party IEEE-488 devices could be connected thanks to the standardized bus. This ecosystem of peripherals reflected the PET’s positioning as more than just a hobbyist computer—it was marketed as a complete business workstation, with robust, intelligent, and expandable hardware surrounding the familiar 6502-based core.

Commodore BASIC was a dialect of Microsoft BASIC, licensed by Commodore in 1977 for use in the PET 2001. It ran from ROM, freeing all RAM for user programs, and provided an immediate programming environment upon power-up. The interpreter was built on the 6502 processor, with tightly coded routines for tokenization, line storage, and execution. This structure allowed BASIC statements to be entered interactively, stored in memory as linked line records, and executed sequentially or via branching constructs. Commodore kept this design across its entire 8-bit product line, from the PET and VIC-20 to the Commodore 64 and beyond, creating a sense of continuity between machines.

Historically, Commodore BASIC differed from many other implementations in its limited feature set relative to machine capabilities. For example, the original PET BASIC lacked dedicated graphics or sound commands, requiring programmers to manipulate memory directly through PEEK and POKE. Even later versions, such as BASIC V2 on the C64, still omitted high-level graphics and sound statements, in contrast with Atari BASIC or BBC BASIC, which provided structured access to system hardware. Only with extended versions such as BASIC 3.5, 4.0, and 7.0 did Commodore add disk commands, string handling improvements, and more advanced features.

When compared to contemporaries, Commodore BASIC was often criticized as being underpowered, but its simplicity made it approachable. BBC BASIC, for example, incorporated structured programming constructs and inline assembler, whereas Commodore’s offering retained the line-numbered, unstructured style of early Microsoft BASIC. Atari BASIC, developed separately, emphasized graphics and sound integration through dedicated keywords. Commodore’s approach forced users to learn the underlying memory map, making them more technically literate about hardware but also raising the entry barrier for certain types of applications.

Despite its limitations, Commodore BASIC achieved massive popularity due to sheer reach. Millions of units shipped with it as the only built-in interface, ensuring every user interacted with it directly. Its ubiquity in schools, homes, and small businesses made it a de facto teaching language for a generation. Moreover, the reliance on PEEK and POKE, while cumbersome, fostered a culture of type-in listings and hardware exploration. This combination of accessibility, wide distribution, and necessity cemented Commodore BASIC’s role as one of the most influential programming environments of the late 1970s and 1980s.

• BASIC 1.0 (PET 2001, 1977)

  Computers: Commodore PET 2001
  Features: Essentially a stock Microsoft BASIC interpreter running in ROM, with support for integer and floating-point arithmetic, strings, arrays, and file operations for tape storage.
  Limitations: No disk commands, no advanced error trapping, and no machine-specific extensions. Designed as a minimal environment to ship the PET quickly.

• BASIC 2.0 (VIC-20, C64, C-MAX, 1981–1982)

  Computers: VIC-20, Commodore 64, Commodore MAX Machine
  Features: Nearly identical to BASIC 1.0 with minor bug fixes, provided the same core Microsoft BASIC functionality.
  Limitations: No disk drive commands, no dedicated graphics or sound statements. Hardware had to be accessed through POKE and PEEK.

• BASIC 3.5 (Commodore 16, C116, Plus/4, 1984)

  Computers: Commodore 16, Commodore 116, Commodore Plus/4
  Features: Added graphics and sound commands (GRAPHIC, CIRCLE, PAINT, SOUND, PLAY), integrated disk commands (DLOAD, DSAVE, DIRECTORY), plus utilities like RENUM and TRON/TROFF.
  Limitations: Still line-number oriented and lacked the structured programming richness of competitors like BBC BASIC.

• BASIC 4.0 (PET/CBM Business Series, 1979+)

  Computers: PET/CBM 4000 and 8000 series
  Features: Expanded disk support with DLOAD, DSAVE, DIRECTORY, COPY, and SCRATCH. Improved error handling suitable for commercial environments.
  Limitations: Focused on business and disk operations, no graphics or sound capabilities because target hardware lacked them.

• BASIC 7.0 (C-128, 1985)

  Computers: Commodore 128
  Features: Added high-level graphics (DRAW, CIRCLE, PAINT) and sound (PLAY, SOUND) commands, advanced disk operations, structured programming constructs like WHILE...WEND, RENUM, and support for memory banking and multi-mode operation.
  Limitations: Despite enhancements, still less sophisticated in structured constructs compared to BBC BASIC or contemporary Pascal-like systems.

• BASIC 10.0 (C-65 prototype, 1990–1991)

  Computers: Commodore 65 (prototype, unreleased commercially)
  Features: Extended support for high-resolution graphics and larger color palettes through VIC-III, up to 8 MB memory addressing, advanced string handling, and structured commands.
  Limitations: Never commercially released, so its practical impact was negligible despite advanced features.

SID is short for Sound Interface Device. It is the name of the sound chip that was used in the VC10, the commodore 64 and the Commodore 128. SID was developed by Bob Yannes, an employee of MOS Technology. Bob was not only an engineer but also knew a lot about music. His intention was to create a different sound chip than other devices at the time. He implemented a subtractive synthesis chip. The chip's distinctive sound is easily recognized and was clearly ahead of the ocmpitition. The SID combines analog and digital circuitry that cannot be 100% emulated, even today.

THe MOS Technology 6509 is an enhanced version of the 8-bit 6502 CPU. Using bank switching the 6509 is able to address up to 1MByte of RAM. The 6502 also could do bank-switching, but did so via separate logic circuits, the 6509 had this logic built in. This extra logic made the 6509 difficult to program, and it was mainly used in the Commodore CBM-II line of computers.