Transformer read-only storage (TROS) was a type of

read-only memory Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing sof ...

(ROM) used in the 1960s and early 1970s before

solid-state Solid state, or solid matter, is one of the four fundamental states of matter. Solid state may also refer to: Electronics * Solid-state electronics, circuits built of solid materials * Solid state ionics, study of ionic conductors and their use ...

memory devices were developed.

Overview

TROS was created by IBM as a read-only storage method for storing

microcode In processor design, microcode (μcode) is a technique that interposes a layer of computer organization between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. Microcode is a laye ...

for IBM computers. TROS used stacks of removable

Mylar BoPET (biaxially-oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and aro ...

flexible printed wiring sheets that fitted onto fixed transformer bases. It was used on the

IBM System/360 Model 20 The IBM System/360 Model 20 is the smallest member of the IBM System/360 family announced in November 1964. The Model 20 supports only a subset of the System/360 instruction set, with binary numbers limited to 16 bits and no floating point. In ...

IBM System/360 Model 40 The IBM System/360 Model 40 was a mid-range member of the IBM System/360 family. It was announced on April 7, 1964, shipped in 1965, and withdrawn on October 7, 1977. History On April 7, 1964, IBM announced the IBM System/360, to be availa ...

and the Type 2841 file control unit.

Use

TROS memory was used to store microcode for

mainframe computer A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterpris ...

s and intelligent controllers used to control sophisticated storage devices such as disk drives and tape drives. If there were a bug in the microcode it was possible to rework it by replacing one or more of the printed wiring sheets, thereby changing the contents of the microcode memory.

References

External links

* {{US patent reference , number = 3432830 , issue-date = 1969 , inventor = Charles E Owen, Daniel M Taub, William A Warwick , title = Transformer read-only storage construction
Full text of U.S. Patent 3432830
Computer storage technologies