The UNIVAC Solid State was a magnetic drum-based solid-state computer announced by Sperry Rand in December 1958 as a response to the IBM 650. It was one of the first computers offered for sale to be (nearly) entirely solid-state, using 700 transistors, and 3000 magnetic amplifiers (FERRACTOR) for primary logic, and 20 vacuum tubes largely for power control. It came in two versions, the Solid State 80 (IBM-style 80-column cards) and the Solid State 90 (Remington-Rand 90-column cards). In addition to the "80/90" designation, there were two variants of the Solid State the SS I 80/90 and the SS II 80/90. The SS II series included two enhancements the addition of 1,280 words of core memory and support for magnetic tape drives. The SS I had only the standard 5,000-word drum memory described in this article and no tape drives.
The memory drum had a regular access speed AREA and a FAST ACCESS AREA. A bank of 4,000 words of memory had one set of read/write (R/W) heads to access. The programmer was required to keep track of what words of memory where under the R/W heads and available to be read or written. At worst the program would have to wait for a full revolution of the drum to access the required memory locations. However 1,000 words of memory had four sets of R/W heads requiring only at most a 90-degree turn of the drum to access the required words.
Programming required that any function that changed the contents of a memory location had first to transfer the contents of the affected word from the drum to a static register.
There were three of these registers A X L, to add the values contained in drum memory locations the programmer would transfer the contents of the specific drum location to register A, then the second operand would be copied to the X register. The ADD instruction would be executed leaving the result in the X register. The contents of the X register would then be written back to the appropriate word on the drum.
Both variants included a card reader, a card punch, and the line printer described in this article. The only "console" was a 10-key adding machine-type keypad, from which the operator would enter the commands to boot the computer. That keypad was also used by programmers in the debugging process. There was no operating system as we have come to know them in recent years; every program was completely self-contained, including the boot loader that initiated execution. All programs were loaded from punched cards; even on the SS II, with its tape drives, there was no ability to launch programs from those drives.
The SS II, including two tape drives, weighed about .
Architecture
The UNIVAC Solid State was a two-address, bi-quinary coded decimal computer using signed 10-digit words. Main memory storage was provided by a 5000-word magnetic drum spinning at 17,667 RPM in a helium atmosphere. For efficiency, programmers had to take into account drum latency, the time required for a specific data item, once written, to rotate to where it could be read.
Technology
The Solid State was one of the first commercially produced computers to use mostly solid-state components.