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.
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.
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.