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LGP-30
The LGP-30, standing for Librascope General Purpose and then Librascope General Precision, is 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, at a retail price of $47,000, equivalent to $540,000 in 2024.
The LGP-30 was commonly referred to as a desk computer. Its height, width, and depth, excluding the typewriter shelf, was 33 by 44 by 26 inches (84 by 112 by 66 cm). It weighed about 800 pounds (360 kg), and was mounted on sturdy casters which facilitated moving the unit.
The primary design consultant for the Librascope computer was Stan Frankel, a Manhattan Project veteran and one of the first programmers of ENIAC, assisted by James Cass, at the time a graduate student at Caltech. They designed a usable computer with a minimal amount of hardware. The single address instruction set had only 16 commands. Magnetic drum memory held the main memory, and the central processing unit (CPU) processor registers, timing information, and the master bit clock, each on a dedicated track. The number of vacuum tubes (113) was minimized by using solid-state diode logic, a bit-serial architecture and multiple use of each of the 15 flip-flops.[citation needed]
It was a binary, 31-bit word computer with a 4096-word drum memory. Standard inputs were the Flexowriter keyboard and paper tape (ten six-bit characters/second). The standard 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.[citation needed]
The computer contained 113 electronic tubes and 1450 diodes. The tubes were mounted on 34 etched circuit pluggable cards which also contain associated components. The 34 cards were of only 12 different types. Card-extenders were available to permit dynamic testing of all machine functions. 680 of the 1450 diodes were mounted on one pluggable logic board.[citation needed]
The LGP-30 required 1500 watts operating under full load. The power inlet cord could plug into any standard 115 volt 60-cycle single-phase line. The computer incorporated voltage regulation suitable for powerline variation of 95 to 130 volts. In addition to power regulation, the computer also contained circuitry for a warm-up stage, which minimized thermal shock to the tubes to ensure longer life. The computer contained a cooling fan which directed filtered air through ducts to the tubes and diodes, to extend component life and ensure proper operation. No expensive air conditioning was necessary if the LGP-30 was operated at reasonable temperatures.[citation needed]
Al Barr, professor of Computer Science at Caltech, noted in 2023 the power saving features of the design. "Much of the computer hardware before the LGP-30 used far too many vacuum tubes. Vacuum tubes used a great deal of electrical power, produced a lot of heat, and were fairly unreliable since they frequently burned out like incandescent light bulbs. The LGP-30 used a goodly amount of solid-state diode logic to reduce the number of vacuum tubes, increasing its reliability and decreasing its power use. The hardware design was one of the stepping stones that opened the door to the modern computer revolution."
Each drum word had 32 bit locations, but only 31 were used, permitting a "restoration of magnetic flux in the head" at the 32nd bit time. Since each instruction had only one address, a method was needed to optimize allocation of operands. Otherwise, each instruction would wait a complete drum (or disk) revolution each time a data reference was made. The LGP-30 provided for operand-location optimization by interleaving the logical addresses on the drum, so that two adjacent addresses (e.g., 00 and 01) were separated by nine physical locations. These spaces allowed for operands to be located next to the instructions that used them. The drum had 64 tracks, each with 64 words (sectors). The time between two adjacent physical words was about 0.260 millisecond (ms), and the time between two adjacent addresses was 9 x 0.260 or 2.340 ms. The worst-case access time was 16.66 ms.[citation needed]
Hub AI
LGP-30 AI simulator
(@LGP-30_simulator)
LGP-30
The LGP-30, standing for Librascope General Purpose and then Librascope General Precision, is 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, at a retail price of $47,000, equivalent to $540,000 in 2024.
The LGP-30 was commonly referred to as a desk computer. Its height, width, and depth, excluding the typewriter shelf, was 33 by 44 by 26 inches (84 by 112 by 66 cm). It weighed about 800 pounds (360 kg), and was mounted on sturdy casters which facilitated moving the unit.
The primary design consultant for the Librascope computer was Stan Frankel, a Manhattan Project veteran and one of the first programmers of ENIAC, assisted by James Cass, at the time a graduate student at Caltech. They designed a usable computer with a minimal amount of hardware. The single address instruction set had only 16 commands. Magnetic drum memory held the main memory, and the central processing unit (CPU) processor registers, timing information, and the master bit clock, each on a dedicated track. The number of vacuum tubes (113) was minimized by using solid-state diode logic, a bit-serial architecture and multiple use of each of the 15 flip-flops.[citation needed]
It was a binary, 31-bit word computer with a 4096-word drum memory. Standard inputs were the Flexowriter keyboard and paper tape (ten six-bit characters/second). The standard 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.[citation needed]
The computer contained 113 electronic tubes and 1450 diodes. The tubes were mounted on 34 etched circuit pluggable cards which also contain associated components. The 34 cards were of only 12 different types. Card-extenders were available to permit dynamic testing of all machine functions. 680 of the 1450 diodes were mounted on one pluggable logic board.[citation needed]
The LGP-30 required 1500 watts operating under full load. The power inlet cord could plug into any standard 115 volt 60-cycle single-phase line. The computer incorporated voltage regulation suitable for powerline variation of 95 to 130 volts. In addition to power regulation, the computer also contained circuitry for a warm-up stage, which minimized thermal shock to the tubes to ensure longer life. The computer contained a cooling fan which directed filtered air through ducts to the tubes and diodes, to extend component life and ensure proper operation. No expensive air conditioning was necessary if the LGP-30 was operated at reasonable temperatures.[citation needed]
Al Barr, professor of Computer Science at Caltech, noted in 2023 the power saving features of the design. "Much of the computer hardware before the LGP-30 used far too many vacuum tubes. Vacuum tubes used a great deal of electrical power, produced a lot of heat, and were fairly unreliable since they frequently burned out like incandescent light bulbs. The LGP-30 used a goodly amount of solid-state diode logic to reduce the number of vacuum tubes, increasing its reliability and decreasing its power use. The hardware design was one of the stepping stones that opened the door to the modern computer revolution."
Each drum word had 32 bit locations, but only 31 were used, permitting a "restoration of magnetic flux in the head" at the 32nd bit time. Since each instruction had only one address, a method was needed to optimize allocation of operands. Otherwise, each instruction would wait a complete drum (or disk) revolution each time a data reference was made. The LGP-30 provided for operand-location optimization by interleaving the logical addresses on the drum, so that two adjacent addresses (e.g., 00 and 01) were separated by nine physical locations. These spaces allowed for operands to be located next to the instructions that used them. The drum had 64 tracks, each with 64 words (sectors). The time between two adjacent physical words was about 0.260 millisecond (ms), and the time between two adjacent addresses was 9 x 0.260 or 2.340 ms. The worst-case access time was 16.66 ms.[citation needed]