UNIVAC Solid State
| Company type | Computer |
|---|---|
| Industry | Computer hardware |
| Predecessor | USAF computer (1957) |
| Founded | December 1958 |
| Founder | Sperry Rand |
Area served | Europe, United States |
| Products | Solid State 80, Solid State 90 (SS I and SS II versions) |
| Owner | Sperry Rand |
| Parent | Sperry Rand |
The UNIVAC Solid State was a magnetic drum-driven solid-state computer introduced by Sperry Rand in December 1958, designed to rival the IBM 650. It stood out as one of the first machines promoted as predominantly solid-state, incorporating 700 transistors alongside 3,000 magnetic amplifiers (FERRACTOR) for its core logic functions, complemented by roughly 20 vacuum tubes primarily dedicated to power regulation. Two principal models were available: the Solid State 80, compatible with IBM-style 80-column punch cards, and the Solid State 90, which used Remington-Rand 90-column cards. Each model was further subdivided into two versions—SS I 80/90 and SS II 80/90. The SS II featured an additional 1,280 words of core memory and support for magnetic tape drives, whereas the SS I depended exclusively on a 5,000-word drum memory and did not support tape drives.
Memory was structured around a drum divided into a standard access segment and a FAST ACCESS AREA. A segment containing 4,000 words was accessed via a single set of read/write (R/W) heads, requiring programmers to monitor which words were positioned under the heads to optimize retrieval times. In the worst case, access latency could extend to a full drum rotation; however, a faster section comprising 1,000 words employed four R/W head sets, thereby limiting maximum wait time to only a quarter of a revolution. Programming necessitated moving any altered word from the drum into one of three static registers—A, X, or L—for processing before writing the updated data back onto the drum.
Both versions came equipped with a card reader, card punch, and line printer. The operator’s interface was confined to a 10-key adding machine-style keypad utilized for bootstrapping commands and debugging purposes. There was no contemporary operating system; all software packages were self-contained and included their own boot loaders. Programs were exclusively loaded from punched cards; even on the SS II, tape drives could not be used to initiate program execution.
The SS II configuration with two tape drives had an approximate weight of .
Architecture
The UNIVAC Solid State operated as a two-address system using bi-quinary coded decimal representation with signed 10-digit words. Its primary memory consisted of a 5,000-word magnetic drum rotating at 17,667 RPM within a helium-filled enclosure. Programmers needed to account for drum latency—the time delay caused by waiting for data to rotate into position—to ensure efficient processing.
Technology
The Solid State stood among the earliest commercial computers to employ predominantly solid-state components. Nonetheless, much of its logical circuitry relied on magnetic amplifiers rather than transistors due to early germanium transistors’ inconsistency and unreliability. These magnetic amplifiers incorporated small toroidal stainless steel cores wrapped with moly-permalloy magnetic alloy and copper windings.
Operating these amplifiers required high-current clock pulses that early transistor technology could not generate. The system clock originated from a timing track on the main storage drum and was amplified through driver tubes (6146 power pentodes) followed by a main clock power amplifier composed of six 4CX250B metal/ceramic power tetrode tubes arranged in push-pull parallel configuration, delivering roughly one kilowatt of power. This high-voltage clock signal was then stepped down via oil-immersed transformers throughout the machine to produce a 36-volt high-current clock distribution. The SS80/90 emitted radio frequency interference detectable on AM bands at frequencies of 707 kHz and 1414 kHz. Its power supply provided -1.6 kV cathode and -800 V screen grid outputs rated at 1.8 A capacity; this unit weighed close to 100 pounds and was installed atop the power supply assembly. Consequently, the SS80/90’s fundamental operation relied heavily on the very technology it aimed to supplant—a noteworthy aspect from a marketing perspective.
Applications
Conceived as the successor to a USAF computer delivered in 1957 to Lawrence G. Hanscom Field near Cambridge, Massachusetts, the Solid State was manufactured in two variants: the Solid State 80, designed for IBM-Hollerith 80-column cards, and the Solid State 90, compatible with Remington-Rand 90-column cards. Together, these models were referred to as the Solid State 80-90. Primarily marketed across Europe, this system aimed at the broad business computing sector. During the early 1960s, UNIVAC SS80/90 machines were deployed at various institutions such as DC Transit, the Small Business Administration (SBA), and the Communications Workers of America (CWA) in Washington DC.
Peripherals
The line printer delivered output at a rate of 600 lines per minute by utilizing a continuously spinning print drum that contained letters, numerals, and punctuation marks arranged for each print column. Each printed line comprised 132 flat-faced hammers spaced at ten characters per inch and activated by solenoids. When the appropriate character reached the printing position on the drum, a thyratron triggered the solenoid to drive the hammer against the paper and an ink ribbon, imprinting the character before the hammer retracted to prepare for the next print cycle. Misalignment of characters vertically could occur due to improper calibration or wear of components.
The card punch device was capable of processing up to 150 punched cards per minute. Precise synchronization was essential among the card punch, reader, and printer—each an electromechanical apparatus. Manufactured by Bull, which held patents for 80-column punch card machinery, it came in two configurations: the P147 model featuring an electromagnetic clutch and the P67 model employing a solenoid-driven mechanical "dog" clutch to initiate punch cycles. The P67’s clutch mechanism resulted in more frequent timing errors compared to the P147. Routine maintenance involved replacing worn taper pins and recalibrating timing due to gear and cam deterioration. The unit incorporated preread, punch, and checkread stations and demanded skilled diagnostic expertise.
While Bull’s punch machine serviced the UNIVAC Solid State 80 with its 80-column cards, the Solid State 90 utilized Univac’s proprietary "Tower Punch" for handling 90-column cards. Operating at a speed of 150 cards per minute, this Tower Punch included mechanical pin sensing at both pre-punch and post-punch read stations, allowing it to read cards, add punched data, and verify accuracy within a single operational cycle.
See also
References