This project aims to make a Alfaskop 4110 running towards the Hercules IBM mainframe emulator and run the Memo mail software by Verimation.
The Alfaskop terminal was a big success for the early Swedish IT industry. The product was originally developed by SRT, Standard Radio & Telefon AB which was an ITT owned company. Later the Alfaskop part was moved in to the partly state owned Stansaab. Which then became DataSAAB. DataSAAB was bought by Ericsson to be part of the EIS business unit. Later on when Ericsson concetrated resources on telecom the EIS unit was sold to Nokia. Eventually Nokia part became ICL and the terminal division ended up in terminal manufacturer Wyse Technologies.
In total 900 000 units were delivered world wide. More information about the Alfaskop Series 41, marketing material and technical documents can be found here.. The development of the Alfaskop series of terminals started in the late 1960ies. The first displays, 3100, emulated the IBM 2260 series of terminals. Later models 3500 and 3700 emulated the IBM 3275 and IBM 3277 terminals. S/41 (4100) series emulated te IBM 3278 and IBM 3279 terminals. The S/41 series evolved in into the S/91 seires, with similar capabilities as the S/41 but in more modern hardware.
The Memo software was originally developed by Volvo IT in the late 1970ies. At its peak in 1992 over 800 of the largest coporations in the world used Memo Mail. Memo mail is still developed and maintained by Verimation AB. A text on Memo mail and other early mail systems developed.
The Hercules project aims at emulating the IBM mainframes with its roots in the IBM S/360 architecture. This architecture has seens extensive development since the mid 1960ies when it was introduced. First by the S/370 series and then onto today with the z-series.
There are today not one single Alfaskop Series 41 terminal that is able to run and show what is was like. The root cause is that the system as a whole was quite complex. The system 41 terminal of Display Unit (DU) requires a communication processor and a floppy drive (FD) to be able to run. It also has no software built in but loads this from the cluster. Interfacing towards the cluster is quite complex. It uses synchronous communication and requires specialized hardware to communicate. All these factors jointly most likely made most of these units end up in the trash rather than saved.
Since the system has had an important role in the Swedish IT industry it would be very intersting to show how this system could operate in reality. We wanted to preserve an operating ALfaskop system and demonstrate it operating with as high fidelity as possible.
The above picture show the overall system architecture. It involves tha full Alfaskop cluster with floppy unit and cluster controller together with the terminal itself. The cluster connects using synchronous BSC communication. A small STM32 microcontroller takes care of the BSC protocol. It handles the byte synchronization and the CRC generation and checking. The data is then sent over a ordinary asnynchronous serial line to the Raspberyy Pi serial port. Inside the Raspberry Pi the socat software takes the data from the serial ports and redirects it to the BSC/TCP port of Hercules. Inside Hercules there is an emulation for the IBM 2703 communication unit. The 2703 is controlled by the TCAM software of the MVS operating system. On top of TCAM the TSO, Time Sharing Option, is running which allow users to log in to the system.
The Alfaskop terminals were mostly used for emulating the IBM 3270 terminal series. Although other emulations were available. The software provided from DDHF is the 3270 BSC variant. The 3270 data stream is described in this document. The documentatation for the IBM 3274 Control Unit provide relevant information on how the communication towards the host takes place. The communicationprocessor could either be connected locally to the IBM main frame or remotely using a dial-up or leased line. In the host end there is a 2703 or 3704 or similar IBM communication unit that interfaces towards the IBM processor. The line normally used 9600 bps syncrounous BSC communication described in this document.
The Alfaskop Series 41 was primarily used as a terminal with emulating various terminal types, like IBM 3278, UNIVAC UTS 400, DEC VT100 etc. The Alfaskop series of terminals were programmed in a special language, SPL. From the beginning this meant StanSAAB Programming Language and was a modified variant of PL/1 programming language. The SPL programming language was developed in PL/1 on a IBM mainframe by a consultant that worked for Stansaab as an under consultant for Programmator around 1977-1978. He worked closely with the person developing the operating system. The operating system was coded entirely in 6800 assembler. The SPL programming language allowed inline assembler constructs if the software developer wanted to improve performance and the compiler has mechanims to do optimizations on the global level.
Later on other software was developed for the Alfaskop series 41, like Alfaword, which was a wordprocessing package. Another package was called Alfaform. These software packages were also coded in the SPL programming language. There was also a port of the UCSD p-system to the System 41 series. Together with FD4120 floppy drive a complete personal computer was formed. The only software found this far is the 3278 terminal emulation software to be used in the clustered configuraration (4016). Unfortunately very little software for the Alfaskop system has been preserved. If you happen to have any software for the Alfaskop series, please get in contact with me.
The system software diskette 4016 has been found at Dansk Datahistorisk Förening. This disk has origninally been with SAS. People at DDHF made an image dump of this disk and provided it to us.
In the beginning of this project we had no access to a CPR4101 neither a FD4120 unit. The initial idea was that based on the software and the scematics that was available an emulation of the floppy unit and cluster controller could be developed in the MAME framework. It turned out to be quite complicated and is still unfinished. The lack of specification of the programmable logic parts turned out to be a major problem since large part of the interrupt handling was taking place in them. When we eventually were able to get our hands on the real units the focus shited to get the full system running and not emulating parts of the cluster. Thus this the old architecture that was envisioned.
The basic idea is to use MAME to emulate the CP and the FD. All technical documentation and schematics are available and is scanned.
To communicate between the various entities of the cluster a TCP variant of the two wire bus will be created eumlating the 32 ports of the CP. To interface to the real Alfaskop DU 4110 a two-wire bus to TCP bridge will be created. In the first implementation it will use an Ericsson TWIB PC board connected to a small uController and a ESP32. Later on the interfacing will be done using a CPLD connected to a ESP32. The CPLD will handle HDLC and include the MODEM.
The special twinax connnector used for the Alfaskop series was devolped by Ossi Carlsson AB, an ELDON AB company. The bus called SS3 which employed a 9.585 MHz (half the pixel clock of the terminal) clock to recover the approximately 300 kbit/s signal modulated by FFSK. The signalling over the link employed HDLC. Initially the FFSK modem was implemented using discrete TTL circuits and a bipolar PROM. Later on a Ferranti ULA (custom IC) was designed which did the entire modulation and demodulation process.
In an attempt to interface to the SS3 bus the easiest was to actually reuse one of the Ericsson made TWIB PC-bus boards that happened to be available. The board is very simple and has just the Intel 8274 HDLC chip and some adress decoding as well as DMA and interrupt logic. Apart for that there is also a twin wire MODEM circuitry including the Ferranti ULA.