MCS Alpha 1

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The Alpha-1 from MCS, the high CPU card at the top right is only partially visible.

The ALPHA-1 from the Berlin company MCS ("Micronic Computer Systems GmbH") is an early home computer that came onto the market in 1977 . It is heavily inspired by the design of the KIM-1 , but has been significantly improved and expanded. In contrast to the systems available at the time, the Alpha was ready for use immediately after unpacking.

General

The ALPHA-1 was offered in three versions: Type 1 in an aluminum housing with an attached CPU card, Type 2 in an aluminum housing with a built-in CPU card, Type 3 and Type 1 in a futuristic Plexiglas housing. Type 1 was also offered as a kit.

The scope of delivery included extensive documentation (manual with circuit diagrams and commented monitor listing), the MOS books "Programming Manual" and "Hardware Manual" in German as well as data sheets from MOS Technologies for the 6502 processor and the 6532 I / O modules and ( informative) to the 6520 , which was not installed.

construction

The outstanding features were the aluminum housing, built-in power supply unit and DIN sockets for two cassette recorders, 25-pin connection socket for terminal, printer and tape reader and punch, 20-pin DIL plug for the free port of the 6532 and CPU card in euro card format with 6502 and 1 kilobyte of RAM. All ICs were socketed. A toggle switch was used for the "Keyboard" and " Terminal " operating modes , another influenced the program sequence : in the middle position, programs ran in real time , and a single-step mode or a timer-controlled "slow step mode" was also provided. The built-in " disassembler ", which was able to show the 6502 mnemonics as plain text on the 7-segment display, is a great relief . After pressing the MN key, the display showed, for example, "STA" instead of "A9". Software: The machine language monitor (MONA = MONitor Alpha) is built into a 2 kilobyte EPROM from Texas Instruments (TMS 2716), which still allows itself the luxury of three operating voltages.

In addition to the usual functions, the built-in disassembler should be mentioned, which has to live with the restrictions of the "7-segment alphabet" (letters such as "K" or "X" cannot be displayed). This disadvantage is eliminated when using a video terminal . Type 1 and 3 of the MONA operating system were supplied with a digital clock routine in order to show rapid success in operating the Alpha. Hours , minutes and seconds were entered in three addresses on the " Zeropage ", another address served as a control register and after starting the monitor program in place of FFB2 you had a six-digit digital clock. Instead, an autobaud routine was built into the Alpha Type 2.

Three finished programs were stored on the supplied program cassette: behind "Einarmiger Bandit" and "Bauer Brösel" were the adapted programs "Farmer Brown" and "Bandit" by Jim Butterfield from the " First Book of KIM-1 ". A program was also included to move memory blocks (programs). Additional programs could be purchased, some of which were strongly based on the "First Book of KIM": moon landing, chess, jukebox and meteorite storm are mentioned here. In-house developments such as alarm systems or "freely programmable controls" were also available.

Extensions

MCS developed the CPU board of the Alpha as a European board with a 64-pin VG bar, which could also be used in a 19-inch housing. This system was called "BETA-8" and could be configured extensively. Various ROM, RAM and IO cards were available as additional cards. A video interface and floppies with an associated controller were then further steps towards the development system. BASIC, ASSEMBLER editor, debugger and disassembler were offered as software extensions. A simple I / O adapter with switches and light-emitting diodes and a more complex "I / O tester" were available for the 2 x 8-bit free ports.

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