The Clipper architecture is a 32-bit RISC-like instruction set architecture designed by Fairchild Semiconductor

Fairchild Semiconductor

Fairchild Semiconductor International, Inc. is an American semiconductor company based in San Jose, California. Founded in 1957, it was a pioneer in transistor and integrated circuit manufacturing...

. The architecture never enjoyed much market success, and the only computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 manufacturers to create major product lines using Clipper processors were Intergraph

Intergraph

Intergraph Corporation is an American software development and services company. It provides enterprise engineering and geospatially powered software to businesses, governments, and organizations around the world. Intergraph operates through two divisions: Process, Power & Marine and Security,...

 and High Level Hardware

HLH Orion

The Orion was a series of 32-bit super-minicomputers designed and produced in the 1980s by High Level Hardware Limited , a company based in Oxford, UK...

. The first processors using the Clipper architecture were designed and sold by Fairchild, but the division responsible for them was subsequently sold to Intergraph in 1987; Intergraph continued work on Clipper processors for use in its own systems.

The Clipper architecture used a simplified instruction set compared to earlier CISC

Complex instruction set computer

A complex instruction set computer , is a computer where single instructions can execute several low-level operations and/or are capable of multi-step operations or addressing modes within single instructions...

 architectures, but it did incorporate some more complicated instructions than were present in other contemporary RISC processors. These instructions were implemented in a so-called Macro Instruction ROM

Read-only memory

Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...

 within the Clipper CPU. This scheme allowed the Clipper to have somewhat higher code density than other RISC CPUs.

Versions

The initial Clipper microprocessor produced by Fairchild was the C100, which became available in 1986. This was followed by the faster C300 from Intergraph in 1988. The final model of the Clipper was the C400, released in 1990, which was extensively redesigned to be faster and added more floating-point registers. The C400 processor combined two key architectural techniques to achieve a new level of performance — superscalar instruction dispatch and superpipelined operation.

Intergraph started work on a subsequent Clipper processor design known as the C5, but this was never completed or released. Nonetheless, some advanced processor design techniques were devised for the C5, and Intergraph was granted patent

Patent

A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

s on these. These patents, along with the original Clipper patents, have been the basis of patent-infringement lawsuits by Intergraph against Intel and other companies.

Unlike many other microprocessors, the Clipper processors were actually sets of several distinct chips. The C100 and C300 consist of three chips: one central processing unit containing both an integer unit and a floating point unit

Floating point unit

A floating-point unit is a part of a computer system specially designed to carry out operations on floating point numbers. Typical operations are addition, subtraction, multiplication, division, and square root...

, and two cache

Cache

In computer engineering, a cache is a component that transparently stores data so that future requests for that data can be served faster. The data that is stored within a cache might be values that have been computed earlier or duplicates of original values that are stored elsewhere...

 and memory management

Memory management

Memory management is the act of managing computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and freeing it for reuse when no longer needed. This is critical to the computer system.Several...

 units (CAMMUs), one responsible for data and one for instructions. The CAMMUs contained caches, translation lookaside buffer

Translation Lookaside Buffer

A translation lookaside buffer is a CPU cache that memory management hardware uses to improve virtual address translation speed. All current desktop and server processors use a TLB to map virtual and physical address spaces, and it is ubiquitous in any hardware which utilizes virtual memory.The...

s, and support for memory protection

Memory protection

Memory protection is a way to control memory access rights on a computer, and is a part of most modern operating systems. The main purpose of memory protection is to prevent a process from accessing memory that has not been allocated to it. This prevents a bug within a process from affecting...

 and virtual memory

Virtual memory

In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...

. The C400 consists of four basic units: an integer CPU, an FPU, an MMU, and a cache unit. The initial version used one chip each for the CPU and FPU and discrete elements for the MMU and cache unit, but in later versions the MMU and cache unit were combined into one CAMMU chip.

Intergraph's Clipper systems

Intergraph sold several generations of Clipper systems, including both server

Server (computing)

In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...

s and workstation

Workstation

A workstation is a high-end microcomputer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems...

s. These systems included the InterAct, InterServe, and InterPro product lines and were targeted largely at the CAD market.

Fairchild promoted the CLIX operating system, a version of UNIX System V

UNIX System V

Unix System V, commonly abbreviated SysV , is one of the first commercial versions of the Unix operating system. It was originally developed by American Telephone & Telegraph and first released in 1983. Four major versions of System V were released, termed Releases 1, 2, 3 and 4...

, for use with the Clipper. Intergraph adopted CLIX for its Clipper-based systems and continued to develop it; this was the only operating system available for those systems. Intergraph did work on a version of Microsoft

Microsoft

Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

 Windows NT

Windows NT

Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It was a powerful high-level-language-based, processor-independent, multiprocessing, multiuser operating system with features comparable to Unix. It was intended to complement...

 for Clipper systems and publicly demonstrated it, but this effort was canceled before release. http://groups-beta.google.com/group/comp.sys.intergraph/msg/2fb2da69ab31c29d Intergraph decided to discontinue the Clipper line and began selling x86 systems with Windows NT instead.