RapidCAD is a specially packaged
Intel 486DX and a dummy
floating-point unit
A floating-point unit (FPU), numeric processing unit (NPU), colloquially math coprocessor, is a part of a computer system specially designed to carry out operations on floating-point numbers. Typical operations are addition, subtraction, multip ...
(FPU) designed as pin-compatible replacements for an
Intel 80386
The Intel 386, originally released as the 80386 and later renamed i386, is the third-generation x86 architecture microprocessor from Intel. It was the first 32-bit computing, 32-bit processor in the line, making it a significant evolution in ...
processor and
80387
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 work in tandem with corresponding x86 CPUs. These m ...
FPU. Because the i486DX has a working on-chip FPU, a dummy FPU package (the "RapidCAD-2") 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. Other source reports that the performance range from 20 to 170 percent faster than the regular Intel386 DX based computers. It was available at manufacturer's suggested list price of US$499.
Technical specifications
;Intel RapidCAD-1
* Package: 132-pin CPGA
* CPU clock: 16–33 MHz
[Intel Corporation, "New Product Focus: End User: CAD Programs Blast Off With Engineering Coprocessor", Microcomputer Solutions, March/April 1992, page 10-11]
* Transistors: 800,000
* Process: CHMOS 0.8 μm
* Voltage: 5 V
* sSpec: SZ624
;Intel RapidCAD-2
* Package: 68-pin CPGA
* CPU clock: 16–33 MHz
* Transistors: 275,000
* Process: CHMOS
* Voltage: 5 V
* sSpec: SZ625
See also
*
Intel 80486 OverDrive
*
Pentium OverDrive
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 Intel 80486, 486 motherboards, and later some Pentium compatible pr ...
References
External links
CPU Shack – The CPU Museum: Intel RAPIDCAD
{{Intel processors, discontinued
RapidCAD
32-bit microprocessors
Computer-related introductions in 1992
Coprocessors
Floating point