PET 2001
The Commodore PET 2001 ( P ersonal E lectronic T ransactor ; German about personal electronic executive agent ) was introduced in January 1977, has been marketed since June 1977 for $ 795. This makes it the world's second mass-produced personal computer ( PC ) that is affordable for private households . However, it is the world's first PC in a fully operational version, as, unlike the first personal computer (the Apple I ) published in April 1976, it was delivered including a housing, power supply unit, keyboard, monitor and mass storage device (in the form of a datasette ).
history
The PET 2001 was primarily developed by Chuck Peddle and presented at the Consumer Electronics Show in early 1977 . Peddle had also developed the predecessor KIM-1 and had previously been a leader in developing the MOS-6502 microprocessor on which all of these devices are based.
With the KIM-1, Peddle had already designed a direct forerunner himself, which he could build on. Compared to the Apple II presented in April 1977 , the PET 2001 had no color, no single-point graphics and no expansion slots , but it could display lowercase letters, was only a quarter as expensive (at least in Europe) and had an intuitive screen in the user interface -Editor , instead of the line editor at Apple that takes getting used to.
The PET had a "parallel IEC bus" ( IEEE-488 connection ) for connecting peripheral devices . In addition to printers and CBM disk drives , measuring devices and other control systems could also be connected to this. This led to the fact that the PET (and a little later especially its direct successor models) was mainly used at universities and research institutions, but also in factories for production control.
The PET 2001 was the first computer that was available from German mail order companies (including from Quelle ). The price was 2,999 DM, later around 2,000 DM. After discovering errors in the BASIC - arrays could reach a maximum size of 256 elements - the price was again reduced considerably.
Excerpt from a brochure of the Vero company (forerunner of Vobis ) from 1979: Take a look around: Everywhere there are still computers that are ten times less expensive than him: Commodore PET 2001, the computer the experts are talking about.
The English word pet also means "pet" or "darling". As Chuck Peddle explained in an interview around 1990, the name was inspired by a joke article that was sold with great success in the USA at the time: Pet Rock , a stone as a pet. The easy-care animal was available in a padded box, including dressage instructions.
Technical specifications
- Metal housing, can be opened up and fixed with a rod (similar to the bonnet of a car)
- Keyboard with letter and number fields, small plastic keys (with metal overlay), which basically came from the desktop computers that Commodore produced at the time. Unlike usual, the keys were placed vertically in columns one below the other instead of offset to the side. This keyboard was given the joking name "Mickey Mouse Keyboard" by users. The later version without a built-in datassette had a 'real' keyboard.
- Built Datassette (tape recorder) for storing data and programs
- CPU : MOS Technology 6502 , 8 bit
- Clock: 1 MHz
- 4 or 8 KiB SRAM depending on the model
- expandable up to 32 KiB (costs 1979: 2,500 DM)
- in Europe only the 8 KB version was sold
- initially with its own chips (MOS 6550) from MOS Technology , but after many heat problems in a later version with third-party chips
- the lowest kilobyte is occupied by the system (including basic), above it freely available to the user, this also applies to successor models
- The Microsoft / Commodore ROM-BASIC is at the same time the operating system and is located in a 14 KiB ROM
- Operating system extensions can be retrofitted in 3 free ROM sockets of 4 KiB each
- Memory usage:
- $00- $ 1FFF 8 KiB RAM (with 4-KiB model only up to $ 0FFF)
- $ 8xxx video RAM (mirrored multiple times)
- $ 9xxx, $ Axxx, $ Bxxx: 3 free sockets
- $ Cxxx, $ Dxxx: 2 × 4 KiB ROM; $ E000- $ E7FF: 2 KiB ROM (Editor)
- $ E800- $ EFFF: 2 KiB memory mapped I / O
- $ Fxxx: 4 KiB ROM, at the end of which a jump table with the most important operating system calls , which was kept compatible up to the C128
- IEEE-488 connection ("parallel IEC bus"), can be used for floppy disk drives and printers
- User port (similar to later with the C64 , 8 bit parallel, handshake bits (with additional software that can be implemented with Centronics output) and TTL monitor output )
- Built-in power supply
- The video part is implemented in discrete TTL technology on the main board, the output is in TTL level (also brought out to the user port ) and with television- compatible ( NTSC ) timing.
- Integrated 9 inch black and white monitor (later also black and green) with 25 lines of 40 characters, successor models from 1979 also with 12 inch monitor (model series CBM 4000 and CBM 8000).
- The device managed without a fan, so that it was completely silent when the datassette was not running.
Programming and software
Programs for the PET 2001 are primarily created in the BASIC programming language . A few seconds after switching on, a PET 2001 is ready for operation and can receive BASIC commands. Programming in machine language is also possible, either directly via an assembler or from BASIC with the help of the BASIC commands SYS (direct jump to an address), USR, PEEK and POKE (direct reading and writing of a memory address).
When programming in BASIC, the screen serves both as an output device and as a buffer for user input. All outputs visible on the screen can be modified at any time and returned to the computer as user input by pressing the ENTER key. This concept is operating and input (engl. As a screen editor screen editor ), respectively. At that time, competing computers only offered line editors that were much more complicated to use .
Since the PET can only display characters, its graphic capabilities are limited to the display of so-called block graphics . For this purpose, the standard character set contains, in addition to capital letters and playing card symbols, all combinations of 2 × 2 partial squares with which a pseudo-resolution of 80 × 50 points can be displayed. An alternatively usable character set offers uppercase and lowercase letters without graphic symbols.
Finished software was only available for the play area. The moon landing game , which simulated a moon landing, and slot machine games ( sinking ships ) were popular. One made do with self-programming or typing in programs from Funkschau , ELO or Chip , the latter two being the only German computer magazines in 1979 alongside the American magazines Creative Computing and Byte . At this time, the first computer program on German television was established: the WDR Computer Club with Wolfgang Back and Wolfgang Rudolph . There programs were also sent in the form of acoustic signals, which - recorded with the microphone or a connecting cable on a music cassette - could later be read into the PET via a data set and executed.
When programming the PET, the requirements of the time quickly reached limits. After switching on, a PET 2001 with a memory expansion of 8 KiB reports "7167 bytes free". Since the program and data have to share this memory, small projects often fail - from today's perspective - due to the limited storage capacity of the PET. It was not uncommon for two versions of a program to be produced: a clear and documented version (one command per line, many comments) and a working version, in which bytes were saved wherever possible by using several commands per line and omitting comments.
The operating software of the PET 2001 is divided into the BASIC interpreter and the so-called Kernal, which at that time was still called the Kernel internally at Commodore and was only later (at the time of the VC-20 ) the name Kernal . The Kernal represents, so to speak, the PET operating system. It contains the software for system initialization and for hardware-related input and output. The Kernal is also responsible for the screen editor.
The BASIC interpreter of the PET originally comes from Microsoft and was adapted to the Kernal by Commodore . It occupies 8 KiB of the 14 KiB ROM and shows some unusual behavior in its first version. For example, the execution of the line
20 IF F OR I=8 GOTO 80
to the message Syntax Error , because the BASIC interpreter as
20 IF FOR I=8 GOTO 80
is interpreted. It is controversial whether one can speak of an error with this behavior: some say the entered line is syntactically correct and should not lead to an error message, others claim that this behavior is well documented and cannot be viewed as an error.
The working speed of the BASIC interpreter of the PET is slow at around one millisecond per BASIC command from today's perspective, as is the loading of programs with two minutes for 8 KiB. For example, the version of the game Space Invaders reprogrammed in BASIC ran very slowly. Applications programmed in machine language, however, allow significantly higher execution speeds. For example, there is a chess program that is more than sufficient for amateurs with its skill level.
In order to enable the compatibility of machine programs on 8-bit computers from Commodore over several Kernal versions and computer generations, there is a jump table at the end of the ROM area (i.e. immediately before the address $ FFFA) , via which the most important kernel Routines can be called. Commodore kept this jump table up to the C128 . For example, the machine command JSR $FFD2 on every 8-bit Commodore computer outputs the contents of the accumulator as ASCII characters on the screen. Unfortunately, this did not improve the compatibility of application software very much because many programmers - mainly for speed reasons - simply ignored this compatible method of calling.
Games
Like the later CBM series, the PET only had character set and no pixel graphics. Therefore, graphic elements had to be realized by cleverly combining special characters. Usually the so-called quarter point graphic was used for this: Since there were twelve special characters, each of which had a quarter, half or three quarters of the area of the cursor (ie one character) filled, including the characters for an empty or fully filled one Cursor graphics are generated with twice the number of lines and columns compared to text display (ie with four times the resolution).
The shift register of the VIA 6522 was often used for sound generation. All that was needed was to connect an amplifier to the user port in order to be able to generate tones consisting of square-wave signals. Later CBM models already had a piezo loudspeaker connected to the circuit board. The later PCs used a similar process.
Although the PET was not a classic game computer, a few dozen games were developed and shipped on cassette and sometimes floppy disk, mainly by Scott Adams and Avalon Hill .
Outstanding projects realized in assembler are a chess program or a space combat simulation in pseudo-3D with Star Wars motifs.
Many of the arcade, console, board and card game classics of the time were ported by private users, including numerous adventures , programs from the Unix world (Startrek, Space War ), small animated films and reaction games (cowboy duel, clown quest) as well as a successful one Implementation of Space Invaders (whose BASIC version was very slow due to the system).
emulation
With emulators like VICE and MESS the PET 2001 can be emulated on current computers.
Successor models
Due to good sales in the USA and Canada, the PET series was also introduced in Europe. However, there was a conflict with Philips there , as this company had already secured the rights to the name "PET" (there, the abbreviation for program development terminal). The models were renamed “CBM” ( C ommodore B usiness M achines ).
The upwardly compatible successor to the PET 2001 was the CBM 3001 . With a view to office applications, Commodore further developed the PET 2002 to the office series CBM 4016/4032 and 8016/8032 , to which floppy disk drives (5¼ ", also 8") could be connected and which had a professional typewriter keyboard. From the 4000 series there was also an improved Commodore BASIC with various commands for using diskettes.
The PET series was discontinued in 1982. The CBM-II series was planned as the successor, but had little success because of the beginning of the dying of non- IBM PC- compatible business computers . Soon afterwards, Commodore also relied on IBM-compatible models in the business segment.
With a view to the home computer market, especially the ability to play computer games on the PET 2001, the VC20 was released in January 1981 and the C64 in December 1982 , both based on the architecture of the PET 2001, but not with the exception of the simplest programs are compatible with PET (or with each other).
literature
- Brian Bagnall: People's Computer: The Rise and Fall of the Computer Pioneer Commodore. Gameplan, Utting 2011, ISBN 978-3-00-023848-2 . Dedicated to the development and success of PET 2001.
- Boris Kretzinger: Commodore. The rise and fall of a computer giant. A short foray into the company's history with data, facts and the reasons why the computer pioneer failed in the end. Scriptorium-Verlag, Morschen 2005, ISBN 3-938199-04-0 ( Edition “Retrobooks” - reading feed for computer lovers 1).
Web links
- Photos and more information about the calculator
- The PET 2001 at Old-Computers.com
- PET 2001 manual for download (PDF) (709 kB)
- More detailed information on PET 2001
- Detailed repair description of a PET 2001
Individual evidence
- ↑ oldcomputers.net
- ↑ Commodore PET - The Worlds First Personal Computer , commodore.ca
- ↑ Steven Levy : Hackers: Heroes of the Computer Revolution. Doubleday 1984, ISBN 0-385-19195-2
- ↑ Steve Wozniak : " iWoz: How I invented the personal computer and co-founded Apple. ", Deutscher Taschenbuchverlag, October 2008, ISBN 978-3-423-34507-1
- ↑ Special Issue 91 . In: 64'er . No. 91 , 1993, p. 10 .
