The Commodore CBM 8096SK was one of the last models in the PET/CBM 8000 series, introduced in the early 1980s. Like the 8096 before it, it featured a MOS 6502A CPU clocked at 1 MHz, Microsoft BASIC 4.0 in ROM, and an 80×25 character display driven by dedicated video circuitry. The “SK” designation stood for Separaterabare Konstruktion (German for “separable construction”), indicating its redesigned two-piece case: a detachable monitor and system unit instead of the earlier all-in-one chassis. Internally, the 8096SK shipped with 96 KB of RAM, of which 32 KB was directly usable by BASIC, while the remaining 64 KB was accessible as a bank-switched memory area—ideal for business applications and languages like FORTRAN and Pascal that needed larger workspaces. This bank-switching mechanism was the defining improvement of the 8096 line over the standard 8032, and the SK inherited and refined it.

Architecturally, the 8096SK remained firmly rooted in the PET/CBM lineage that began with the 3000 and 4000 series. All of these machines shared the same fundamental design: a 6502 processor, memory-mapped video, Microsoft BASIC in ROM, and the IEEE-488 (GPIB) bus for peripherals. The progression from the 3000/4000 to the 8000 series primarily expanded screen width (from 40 to 80 columns) and memory size, while retaining the same overall bus layout and software compatibility. The 8096SK represented the mature end of this architecture—essentially a “big PET” with more RAM, a professional case design, and compatibility with the software ecosystem built for earlier CBM machines. It closed the gap between the PET-style business computers and Commodore’s later CBM-II series, which moved toward a new hardware base.

The biggest difference of the 8000 series over the 4000 series is that the 8000 models had a 12" screen as standard, and Basic 4.0. The CPU was the same 6502 running at 1 MHz, but improved circuitry allowed the 8000 series to run significantly faster. The case of the 8096-SK is rounded as opposed to the more square cornered 8096, and is rumored to be designed by the Porche Design team, although evidence is not clear.

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.

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.

The Commodore CBM 8n96 (8096SK, 8296D) were a PET/CBM business machines with a 6509 CPU (The bank-switch derivative of the 6502). In addition, Commodore and third parties offered plug-in boards that added extra CPUs such as the Z80 and the Intel 8088.

Z80 co-processor

8088 co-processor

The Z80 quickly became popular in the personal computer market, with many early personal computers, such as the TRS-80 and Sinclair ZX80, using the Z80 as their central processing unit (CPU). It was also widely used in home computers, such as the MSX range, SORD, and the Amstrad CPC, as well as in many arcade games. Additionally, it was also used in other applications such as industrial control systems, and embedded systems. The Z80 was widely used until the mid-1980s, when it was gradually replaced by newer microprocessors such as the Intel 80286 and the Motorola 68000.

The Z80 microprocessor was developed by Zilog, a company founded by Federico Faggin in 1974. The Z80 was released in July 1976, as a successor to the Intel 8080. It was designed to be fully compatible with the 8080, but also included new features such as an improved instruction set, more powerful interrupts, and a more sophisticated memory management system.

Originally the Z80 was intended for use in embedded systems, just as the 8080 CPU. But the combination of compatibility, superior performance to other CPUs of the era, and the affordability led to a widespread use in arcade video game systems, and later in home computers such as the Osborne 1, TRS-80, ColecoVision, ZX Spectrum, MSX, Sega's Master System and many more. The Z-80 ran the original Pac-Man arcade cabinet. The Z-80 was used even in the Game Gear (1990s), and the TI-81 and succeeding graphic calculators.

The Z-80 remained in production until June of 2024, 48 years after its original release. Zilog replaced the processor with its successor the eZ80, an 8-bit microprocessor that features expanded memory addressing up to 16 megabytes, and running up to 50MHz, comparable to a Z80 clocked at 150MHz.

The Intel 8088 microprocessor is a variant of the Intel 8086. The 8088 has an 8-bit external bus instead of the 16-bit bus that the 8086 has. The 16-bit registers and the 1MByte address range are unchanged, however. The 8086 and the 8088 have the same execution unit (EU), only the Bus Interface Unit (BIU) differs.

The original IBM PC architecture is based on the Intel 8088. The CPU runs at 5 to 16 MHz, has a 20-bit address bus and can work together with the 8087 Co-Processor. The 8088 was launched in 1979. The 8088 is compatible with the Intel 8085.