RPC-4000

The LGP-30, standing for Librascope General Purpose and then Librascope General Precision, was an early off-the-shelf computer. It was manufactured by the Librascope company of Glendale, California (a division of General Precision Inc.), and sold and serviced by the Royal Precision Electronic Computer Company, a joint venture with the Royal McBee division of the Royal Typewriter Company. The LGP-30 was first manufactured in 1956 with a retail price of $47,000—equivalent to about $414,000 today.

The LGP-30 was commonly referred to as a desk computer. It was 26 inches (660 mm) deep, 33 inches (840 mm) high, and 44 inches (1120 mm) long, exclusive of the typewriter shelf. The computer weighed approximately 740 pounds (340 kg) and was mounted on sturdy casters which facilitated movement of the computer.

The primary design consultant for the Librascope computer was Stan Frankel, a Manhattan Project veteran and one of the first programmers of ENIAC. He designed a usable computer with a minimal amount of hardware. The single address instruction set had only 16 commands. Not only was the main memory on magnetic drum, but so were the CPU registers, timing information and the master bit clock, each on a dedicated track. The number of vacuum tubes were kept to a minimum by using solid-state diode logic, a bit-serial architecture and multiple usage of each of the 15 flip-flops.

It was a binary, 31 bit word computer with a 4096 word drum memory. Standard inputs were the Flexowriter keyboard and paper tape (ten 6-bit characters/second). The only printing output was the Flexowriter printer (typewriter, working at 10 characters/second). An optional higher speed paper tape reader and punch was available as a separate peripheral.

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