RapidCAD is a specially packaged Intel 486DX and a dummy floating point unit (FPU) designed as pin-compatible replacements for an Intel 80386 processor and 80387 FPU. Because the i486DX has a working on-chip FPU, a dummy FPU package is supplied to go in the Intel 387 FPU socket. The dummy FPU is used to provide the FERR signal, necessary for compatibility purposes.
Despite being able to execute instructions in the same number of cycles as an i486DX, integer performance on RapidCAD suffers due to the absence of level 1 cache and the bottleneck of the 386 bus. RapidCAD offers minimal improvement in integer performance over a 386DX (typically 10%, at most 35%), but provides substantial improvement in floating point operations (up to 80% faster) for which it was marketed. Floating point performance is mostly improved by moving the FPU onto the CPU core.
This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.
Athlon is the brand name applied to a series of x86-compatible microprocessors designed and manufactured by Advanced Micro Devices (AMD). The original Athlon was the first seventh-generation x86 processor and was the first desktop processor to reach speeds of one gigahertz (GHz). It made its debut on June 23, 1999.
The Cyrix 6x86 is a sixth-generation, 32-bit x86 microprocessor designed by Cyrix and manufactured by IBM and SGS-Thomson. It was originally released in 1996.
The Intel 80386, also known as i386 or just 386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistors and were the CPU of many workstations and high-end personal computers of the time. As the original implementation of the 32-bit extension of the 80286 architecture, the 80386 instruction set, programming model, and binary encodings are still the common denominator for all 32-bit x86 processors, which is termed the i386-architecture, x86, or IA-32, depending on context.
The Intel 80486, also known as the i486 or 486, is the successor model of 32-bit x86 microprocessor to the Intel 80386. Introduced in 1989, the 80486 improved on the performance of the 80386DX thanks to on-die L1 cache and floating-point unit, as well as an improved, five-stage tightly-coupled pipelined design. It was the first x86 chip to use more than a million transistors. It represents the fourth generation of binary compatible CPUs since the original 8086 of 1978.
Intel's i486SX was a modified Intel 486DX microprocessor with its floating-point unit (FPU) disabled. It was intended as a lower-cost CPU for use in low-end systems. Computer manufacturers that used these processors include Packard Bell, Compaq, ZEOS and IBM.
The first Pentium microprocessor was introduced by Intel on March 22, 1993. Its P5 microarchitecture was the fifth generation for Intel, and the first superscalar IA-32 microarchitecture. As a direct extension of the 80486 architecture, it included dual integer pipelines, a faster floating-point unit, wider data bus, separate code and data caches and features for further reduced address calculation latency. In October 1996, the Pentium with MMX Technology was introduced, complementing the same basic microarchitecture with the MMX instruction set, larger caches, and some other enhancements.
The Intel i486DX2, rumored as 80486DX2 is a CPU produced by Intel that was introduced in 1992. The i486DX2 was nearly identical to the i486DX, but it had additional clock multiplier circuitry. It was the first chip to use clock doubling, whereby the processor runs two internal logic clock cycles per external bus cycle. An i486 DX2 was thus significantly faster than an i486 DX at the same bus speed thanks to the 8K on-chip cache shadowing the slower clocked external bus.
The Intel i860 was a RISC microprocessor design introduced by Intel in 1989. It was one of Intel's first attempts at an entirely new, high-end instruction set architecture since the failed Intel iAPX 432 from the 1980s. It was released with considerable fanfare, slightly obscuring the earlier Intel i960, which was successful in some niches of embedded systems, and which many considered to be a better design. The i860 never achieved commercial success and the project was terminated in the mid-1990s.
Cyrix Corporation was a microprocessor developer that was founded in 1988 in Richardson, Texas, as a specialist supplier of math coprocessors for 286 and 386 microprocessors. The company was founded by Tom Brightman and Jerry Rogers. Cyrix founder, President and CEO Jerry Rogers, aggressively recruited engineers and pushed them, eventually assembling a small but efficient design team of 30 people.
The Pentium Pro is a sixth-generation x86 microprocessor developed and manufactured by Intel introduced in November 1, 1995. It introduced the P6 microarchitecture and was originally intended to replace the original Pentium in a full range of applications. While the Pentium and Pentium MMX had 3.1 and 4.5 million transistors, respectively, the Pentium Pro contained 5.5 million transistors. Later, it was reduced to a more narrow role as a server and high-end desktop processor and was used in supercomputers like ASCI Red, the first computer to reach the teraFLOPS performance mark. The Pentium Pro was capable of both dual- and quad-processor configurations. It only came in one form factor, the relatively large rectangular Socket 8. The Pentium Pro was succeeded by the Pentium II Xeon in 1998.
The Pentium OverDrive was a microprocessor marketing brand name used by Intel, to cover a variety of consumer upgrade products sold in the mid-1990s. It was originally released for 486 motherboards, and later some Pentium sockets. Intel dropped the brand, as it failed to appeal to corporate buyers, and discouraged new system sales.
The Am386 CPU is a 100%-compatible clone of the Intel 80386 design released by AMD in March 1991. It sold millions of units, positioning AMD as a legitimate competitor to Intel, rather than being merely a second source for x86 CPUs.
The Intel 8087, announced in 1980, was the first x87 floating-point coprocessor for the 8086 line of microprocessors.
The Motorola 68881 and Motorola 68882 are floating-point coprocessor (FPU) devices that were used in some computer systems in conjunction with the 68020 or 68030 microprocessors. The Motorola 68881 was introduced in 1984. The addition of one of these devices added substantial cost to a computer, but added a floating-point unit that could rapidly perform floating point mathematical calculations. In the mid 1980s, this feature was useful mostly for scientific and mathematical software.
x87 is a floating-point-related subset of the x86 architecture instruction set. It originated as an extension of the 8086 instruction set in the form of optional floating-point coprocessors that worked in tandem with corresponding x86 CPUs. These microchips had names ending in "87". This was also known as the NPX. Like other extensions to the basic instruction set, x87 instructions are not strictly needed to construct working programs, but provide hardware and microcode implementations of common numerical tasks, allowing these tasks to be performed much faster than corresponding machine code routines can. The x87 instruction set includes instructions for basic floating-point operations such as addition, subtraction and comparison, but also for more complex numerical operations, such as the computation of the tangent function and its inverse, for example.
The R4000 is a microprocessor developed by MIPS Computer Systems that implements the MIPS III instruction set architecture (ISA). Officially announced on 1 October 1991, it was one of the first 64-bit microprocessors and the first MIPS III implementation. In the early 1990s, when RISC microprocessors were expected to replace CISC microprocessors such as the Intel i486, the R4000 was selected to be the microprocessor of the Advanced Computing Environment (ACE), an industry standard that intended to define a common RISC platform. ACE ultimately failed for a number of reasons, but the R4000 found success in the workstation and server markets.
The 386SLC was an Intel-licensed version of the 386SX, developed and manufactured by IBM in 1991. It included power-management capabilities and an 8KB internal CPU cache, which enabled it to yield comparable performance to 386DX processors of the same clock speed, which were considerably more expensive. Known inside IBM as "Super Little Chip" for its initials, it was used in the IBM PS/2 35, 40 and 56 Series and in the IBM PS/ValuePoint 325T, but never gained much market share. This was mainly due to an agreement with Intel, in which IBM was not allowed to sell their CPUs if they were not part of a system or upgrade board. It was also marketed as an optional upgrade for 8086-equipped IBM PS/2 25 Series computers.
The Vortex86 is a computing system-on-a-chip (SoC) based on a core compatible with the x86 microprocessor family. It is produced by DM&P Electronics, but originated with Rise Technology.
The R4200 is a microprocessor designed by MIPS Technologies, Inc. (MTI) that implemented the MIPS III instruction set architecture (ISA). It was also known as the VRX during development. The microprocessor was licensed to NEC, and the company fabricated and marketed it as the VR4200. The first VR4200, an 80 MHz part, was introduced in 1993. A faster 100 MHz part became available in 1994. The R4200 was developed specifically for low-power Windows NT computers such as personal computers and laptops. MTI claimed the microprocessor's integer performance was greater than that of a high-end Intel i486 and 80% of a P5-variant Pentium microprocessor. The R4200 ultimately did not see any use in personal computers and was repositioned as an embedded microprocessor that competed with the R4600. The R4300i variant was used in the widely popular Nintendo 64 video game console.
The Cyrix Cx486 or Cyrix 486 was an x86-Compatible microprocessor designed by Cyrix to primarily compete with the Intel 486 with which it was software compatible, would operate in the same motherboards provided proper support by the BIOS was available and generally showed comparable performance. The chip also competed with parts from AMD and UMC.