Weitek WTL 4167 co-processor family

Weitek 4167 is a high-performance Floating Point Unit for Intel 80486 family of microprocessors. The 4167 works similar to Weitek 3167 FPU, and offers much better performance (3 - 4 times faster by some estimates) than the 3167. To communicate with the Weitek 4167 the CPU reads from/writes to memory space designated for the FPU. This communication method was beneficial to previous generation of Weitek 3167 FPUs because it was faster than I/O communication method used by 80387 co-processors. On 4167 this communication method became one of FPU disadvantages due to changes in 80486 CPU architecture. In 80486 family the co-processor was integrated with the main processor, thus eliminating communication delay between the CPU and FPU. Other disadvantages of the Weitek 4167 were the same as for the 3167 FPU:

• The 4167 FPU didn't fit into 80486 upgrade socket and required a separate 142-pin socket to be present on the motherboard.
• The Weitek FPU instruction set was different from 80x87 instruction set. All applications compiled for 487 FPU didn't work with the 4167 co-processor. To take advantage of the 4167 FPU the applications had to be re-compiled using a compiler which supported Weitek co-processor.

The 4167 offered better performance than integrated FPU in the 80487 and 80486DX processors, but it lost its performance lead with the introduction of 80486DX2 CPUs.