The 1300 series was a joint venture between ICT, based in Putney and GEC telephones based in Coventry. GEC provided the electronics and ICT the peripherals. A jointly owned design company was set up, Computer Developments Ltd of Kenton, Middlesex. Arthurs serial number is 075, this dates him to the early 60’s.
We know Arthur was used by ICT itself, they ran a bureau service for customers, then to the Liverpool Victoria Friendly Society to join Samantha another ICT 1301 LVFS were already operating.
Architecture : 4 bit parallel by 12 digit serial. Decimal and sd arithmetic.
Clock speed: 1 million cycles per second
Main memory: 2,000 words of 48 bits.
Tape storage: Five magnetic tape drives operating at 75 inches per second.
Data is recorded at 300bits per inch on ten tracks, four inverse data tracks and two parity tracks. This allows single bit errors to be both detected and corrected.
Line printer: 120 column, 600 line per minute printer with 50 different characters.
Card reader: 80 column cards, 600 cards per minute.
Card punch: 80 column cards, 100 cards per minute.
Drum storage: 12,000 words of 48 bits.
A core is a small washer of magnetic material which can be magnetised in either of two directions, thus storing a single binary digit. Three wires were threaded through each one, when an electric current flows through two of the wires the core will be magnetised in a direction dependent on the direction of the current flow. If not already magnetised in that direction, a pulse would be produced in the third wire, allowing the memory to be read. Arthur’s main memory consists of 100,000 of these cores, arranged as 2000 words of 50 bits (48 data and two parity), and all hand-wired!. In modern terminology this is almost 12 Kilobytes. Yes Kilo, not Mega or Giga! With it’s control electronics, the memory weighs about half a ton.
It is also worth remembering that Core Memory is non-volatile. That is, it holds the memory when it is powered down, unlike modern computer memory.
Magnetic Tape Drives
Five magnetic tape drives operating at 75 inches per second. Data is recorded at 300 bits per inch on ten tracks, 4 data tracks, four inverse data tracks and two parity tracks. This allows single bit errors to be both detected and corrected.
The backing store on the ICT 1301 is on a Magnetic Drum, it is powered by a 3/4 horsepower three phase motor driving the drum at a speed of 5,250 rpm. Each drum holds 12,000 words of 48 bits. Around the drum are 240 read/write heads which are fixed in position, unlike modern disks which move their heads to access different tracks on their flat media. This would be equivelent to around 72kBytes of storage using todays formats. The drive unit weighs around 300kg.
The ICT 1301 can make use of many peripherals. These include the IBM 082 Card Sorter, and the IBM 129 Card Reader/Writer.
I Would like to thank Roger Holmes owner of Flossie, currently the last working ICT 1301 for proving the information and specification’s of Arthur.
ICT 1301 Photos Part 1
ICT 1301 Photos Part 2
ICT 1301 Photos Part 3