ICT 1900 series

The 1900 series was notable for being one of the few non-American competitors to the IBM System/360, enjoying significant success in the European and British Commonwealth markets.

In order to sweeten the deal, Ferranti demonstrated to ICT the Ferranti-Packard 6000 (FP6000) machine, which had been developed by its Canadian subsidiary Ferranti-Packard, to a design known as Harriac that had been initiated in Ferranti by Harry Johnson and fleshed out by Stanley Gill and John Iliffe.

Another plan being considered was to license a new range of machines being developed by RCA, probably compatible with the expected IBM 8000.

On 29 September 1964 the ICT 1900 range was announced in a filmed presentation, scripted by Antony Jay.

The first commercial sale was made in 1964 to the Morgan Crucible Company, comprising a 16K word 1902 with an 80-column 980-card/minute reader, a card punch, a 600 line/min printer and 4 x 20kchar/s tape drives[nb 1].

The accumulators were addressable as if they were the first eight words of memory, giving the effect of register-to-register instructions with no extra operation codes being needed.

The large number of optional features in the FP6000 design gave ICT great flexibility in pricing.

Later models added paging hardware, allowing true virtual memory with the GEORGE 4 operating system.

The largest change between the original FP6000 and the 1900 series was the inclusion of the ICT standard interface for connection of peripherals.

On smaller members of the series, some expensive instructions (floating point for example) were also implemented as extracodes.

In order to deal with data on paper tape or from communications equipment, a system of shifts could be used to represent the full 128 characters of ASCII.

All machines except the 1901 were operated from a modified Teletype Model 33 ASR used to give commands to the executive.

The original discrete germanium semiconductor implementations were replaced by Texas Instruments 7400 series TTL integrated circuits in most of the range and Motorola MECL 10K ECL integrated circuits in the new 1906A (which was based on the original 1906 rather than the dual processor 1904 of the 1906E/F).

There was a proposal to build a multiprocessor version of the 1906A, the 1908A (known internally as Project 51), which would allow ICL to compete with the large CDC and IBM machines in universities and research centers but it was eventually abandoned in favor of accelerating work on the New Range, which was being designed to replace both the 1900 series and the ICL System 4.

During and after the production of the 1900 series a number of compatible (or clone) machines were produced by ICL licensees, as well as competitors.

Based on a fully microprogrammed CPU, the Stanford EMMY commercialised by Palyn Associates, the ME29 was sold as a replacement for the 2903 and 2904, still executing the 1900 order code.

Second generation "S3E" (microcoded) versions of the larger New Range systems (such as the 2960/2966 from West Gorton, and the later 2940/50 from Stevenage), could run 1900 series code under DME (Direct Machine Environment) as an emulation as well as the New Range instruction set under the newer VME (Virtual Machine Environment).

Executive performed all the I/O operations on behalf of user programs, allowing allocation of different peripherals as needed.

Despite its simplicity executive was, for the time, quite powerful, allocating memory to programs as needed (rather than the fixed partitions provided by OS/360).

With the introduction of magnetic disk systems executive became more complex, using overlaying to reduce its memory footprint.

The branch was initially staffed with people being released by the end of work on the OMP operating system for the Ferranti Orion.

George 3 was a complete operating system in itself, it used a much reduced executive responsible only for handling low level hardware access.

George 3 implemented both batch processing and Multiple online programming (MOP) – interactive use from terminals.

Other software was available as paid options from ICT or other sources, including such exotic packages as Storm Sewer Design and Analysis.