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This Commodore PET 2001 also includes the Expansion Memory ExpandaMem made by CompuThink

from Wikipedia homepage:

The Commodore PET (Personal Electronic Transactor) was a home/personal computer produced in 1977 by Commodore International. A top-seller in the Canadian and United States educational markets, it was Commodore’s first full-featured computer, and formed the basis for their entire 8-bit product line.

In the 1970s Commodore was one of many electronics companies selling calculators designed around Dallas-based Texas Instruments (TI) CPU chips. However, in 1975 TI increased the price of these components to the point where the chip set cost more than an entire TI calculator, and the industry that had built up around it was frozen out of the market.

Commodore responded to this by searching for a chip set they could purchase outright. They quickly found MOS Technology, who were in the process of bringing their 6502 microprocessor design to market, and with whom came Chuck Peddle’s KIM-1 design, a small computer kit based on the 6502. At Commodore, Peddle convinced Jack Tramiel that calculators were a dead-end. In September 1976 Peddle got a demonstration of Jobs and Wozniak’s Apple II prototype, when Jobs was offering to sell it to Commodore, but Commodore considered Jobs’ offer too expensive.

Tramiel demanded that Peddle, Bill Seiler, and John Feagans create a computer in time for the June 1977 Consumer Electronics Show, and gave them six months to do it. Tramiel’s son, Leonard, helped design the PETSCII graphic characters and acted as quality control. The result was the first all-in-one home computer, the PET, the first model of which was the PET 2001. Its 6502 processor controlled the screen, keyboard, cassette tape recorders and any peripherals connected to one of the computer’s several expansion ports. The PET 2001 included either 4 kB (2001-4) or 8 kB (2001-8) of 8-bit RAM, and was essentially a single-board computer with discrete logic driving a small built-in monochrome monitor with 40×25 character graphics, enclosed in a sheet metal case that reflected Commodore’s background as a manufacturer of office equipment. Designed on an appliance computer philosophy similar to the original Macintosh the machine also included a built-in Datassette for data storage located on the front of the case, which left little room for the keyboard.

The data transfer rate to cassette tape was 1500 baud, but the data was recorded to tape twice for safety, giving an effective rate of 750 baud. The computer’s main board carried four expansion ports: extra memory, a second cassette tape recorder interface, a parallel port (mainly used for disk drives and printers) and an IEEE-488 port (mainly used for modems).

The PET 2001 was announced at the Winter CES in January 1977 and the first 100 units were shipped later that year in October. However, the PET was back-ordered for months and to ease deliveries, early in 1978 Commodore decided to cancel the 4 kB version (also because the user would be left with barely 3 kB of RAM).

source: wikipedia