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ICL 7500 series
The ICL 7500 series (7501, 7502, 7503, 7561, etc.) was a range of terminals and workstations, that were developed by ICL during the 1970s for their new range ICL 2900 Series mainframe computers. The colour scheme was compatible with the 2900. The term 7561 is a commonly used though loose term for the interactive video aspects of the 7502 series. The 7501 and 7502 systems were known as Modular Terminal Processors in marketing publications. 7501 and 7502 systems were built at Blackhorse Road, Letchworth (1/3 factory).
7502 consisted of a system enclosure containing up to eight PCB's (CPU card, memory cards, peripheral controllers and video cards). It was similar in size to a desk side or tower PC, but was mounted horizontally. As it was intended to function in an office environment, steel-framed, wood-veneered cabinets and furniture were available for the processor and peripheral units. The 7502 system enclosure had two levels to include space for the dual, 8-inch floppy disk unit. The interior of the cabinet was covered with acoustic-absorbent foam material to cut the noise from the cooling fans. The maximum connectivity was 8 x 7561 VDU stations and four serial printers, but in the early systems it was necessary to reduce the VDU attachments if floppy disk storage was attached. The rear of the 7502 system carried the connectors for VDUs, modem and serial printers and a set of 8 "engineer's switches" which could be used to input data and set options for "teleloading" software.
7501 comprised a smaller enclosure integrated beneath a 7561 VDU terminal. It had only 5 card slots in the backplane and offered reduced connectivity with only one additional VDU terminal possible. A narrow operator's console with indicators, rotary-switch and modem control switches was implemented below the VDU screen bezel.
7501 and 7502 were functionally the same and shared identical interfaces and system software. A 4 Kbyte Read-Only Memory (ROM) in the normal address space provided a system bootstrap capable of downloading the operating software over the normal synchronous communications line, loading or dumping from/to local floppy disk or providing a local engineer's console. For diagnostic purposes an Engineer's Test Unit could be installed between the CPU card and the backplane. This gave the engineer full capability of reading and writing registers or memory and single-stepping machine code or CPU microcode. A digital cassette tape device could be used to load test or operating software.
7503 was similar to 7502 but was normally used as for Remote Job Entry. It featured a line printer, card reader and operator console integrated into a larger operators desk. It used totally different hardware and architecture for its processing system. 7503 was developed by a team in Stevenage, while 7502 was developed in Kidsgrove.
7561 VDUs were memory-mapped display monitors, and not character-based terminals. The tube phosphor was green in colour. The keyboards were separate input/output devices whose data was decoded by the operating software to update the screen display or trigger actions by the system. Security identifiers (Personal Identity Device, or PID) based on magnetically-coded pens with a reader at the top right corner of the keyboard unit could be used to provide levels of access-privilege to users. Early 7561/1 VDUs had simple composite-video inputs, while the updated 7561/2 VDU had improved display tubes and interlaced scan. The native screen resolution was 25 lines of 80 characters, but there were options for a 960-character display format.
7502 used a much closer integration between the processor and the display driver circuits. In 7503, the screen updates involved the processor specifying a screen address to the display driver cards, and then firing a sequence of characters to be stored in consecutive locations starting at the specified address. The display driver hardware included hardware registers to track where the next character was to be placed. In 7502, the display memory was part of the processors' normal memory space. This meant that the processor could read or write any screen location directly.
7502 had a number of command functions that allowed the processor to manipulate blocks of memory directly. This allowed the 7502 to move data on the screen very quickly, such as when the screen contents were to be scrolled up, or for rapidly clearing the screen. Similar functions also allowed the screen attributes to be amended in bulk, such as setting blocks of text to flash or to be displayed in italics.
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ICL 7500 series AI simulator
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ICL 7500 series
The ICL 7500 series (7501, 7502, 7503, 7561, etc.) was a range of terminals and workstations, that were developed by ICL during the 1970s for their new range ICL 2900 Series mainframe computers. The colour scheme was compatible with the 2900. The term 7561 is a commonly used though loose term for the interactive video aspects of the 7502 series. The 7501 and 7502 systems were known as Modular Terminal Processors in marketing publications. 7501 and 7502 systems were built at Blackhorse Road, Letchworth (1/3 factory).
7502 consisted of a system enclosure containing up to eight PCB's (CPU card, memory cards, peripheral controllers and video cards). It was similar in size to a desk side or tower PC, but was mounted horizontally. As it was intended to function in an office environment, steel-framed, wood-veneered cabinets and furniture were available for the processor and peripheral units. The 7502 system enclosure had two levels to include space for the dual, 8-inch floppy disk unit. The interior of the cabinet was covered with acoustic-absorbent foam material to cut the noise from the cooling fans. The maximum connectivity was 8 x 7561 VDU stations and four serial printers, but in the early systems it was necessary to reduce the VDU attachments if floppy disk storage was attached. The rear of the 7502 system carried the connectors for VDUs, modem and serial printers and a set of 8 "engineer's switches" which could be used to input data and set options for "teleloading" software.
7501 comprised a smaller enclosure integrated beneath a 7561 VDU terminal. It had only 5 card slots in the backplane and offered reduced connectivity with only one additional VDU terminal possible. A narrow operator's console with indicators, rotary-switch and modem control switches was implemented below the VDU screen bezel.
7501 and 7502 were functionally the same and shared identical interfaces and system software. A 4 Kbyte Read-Only Memory (ROM) in the normal address space provided a system bootstrap capable of downloading the operating software over the normal synchronous communications line, loading or dumping from/to local floppy disk or providing a local engineer's console. For diagnostic purposes an Engineer's Test Unit could be installed between the CPU card and the backplane. This gave the engineer full capability of reading and writing registers or memory and single-stepping machine code or CPU microcode. A digital cassette tape device could be used to load test or operating software.
7503 was similar to 7502 but was normally used as for Remote Job Entry. It featured a line printer, card reader and operator console integrated into a larger operators desk. It used totally different hardware and architecture for its processing system. 7503 was developed by a team in Stevenage, while 7502 was developed in Kidsgrove.
7561 VDUs were memory-mapped display monitors, and not character-based terminals. The tube phosphor was green in colour. The keyboards were separate input/output devices whose data was decoded by the operating software to update the screen display or trigger actions by the system. Security identifiers (Personal Identity Device, or PID) based on magnetically-coded pens with a reader at the top right corner of the keyboard unit could be used to provide levels of access-privilege to users. Early 7561/1 VDUs had simple composite-video inputs, while the updated 7561/2 VDU had improved display tubes and interlaced scan. The native screen resolution was 25 lines of 80 characters, but there were options for a 960-character display format.
7502 used a much closer integration between the processor and the display driver circuits. In 7503, the screen updates involved the processor specifying a screen address to the display driver cards, and then firing a sequence of characters to be stored in consecutive locations starting at the specified address. The display driver hardware included hardware registers to track where the next character was to be placed. In 7502, the display memory was part of the processors' normal memory space. This meant that the processor could read or write any screen location directly.
7502 had a number of command functions that allowed the processor to manipulate blocks of memory directly. This allowed the 7502 to move data on the screen very quickly, such as when the screen contents were to be scrolled up, or for rapidly clearing the screen. Similar functions also allowed the screen attributes to be amended in bulk, such as setting blocks of text to flash or to be displayed in italics.
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