The 3167 was introduced in 1989 to provide the fastest floating point performance possible on a 386 based system at that time. The Weitek Abacus is not a real coprocessor, strictly speaking, but rather a memory mapped peripheral device. It was optimized for speed wherever possible. Besides using the faster memory mapped interface to the CPU (the 80x87 uses IO-ports), it does not support many of the features of the 80x87 coprocessors, allowing all of the chip's resources to be concentrated on the fast execution of the basic arithmetic operations.
The Weitek Abacus provided up to 2.5 times the performance of an Intel 387DX coprocessor, but it's performance would drop to about half the stated rate for double precision, while the value for the Intel 387DX would not change much. Anyhow, before the advent of the Intel RapidCAD, the Weitek 3167 usually beat all 387 compatible coprocessors even for double precision operations. For typical applications the advantage of the Weitek 3167 over the 387 clones is much smaller.
The Abacus 3167 is packaged in a 121-pin PGA that fits into an EMC socket provided by most 386 based systems. It does not fit into the normal coprocessor socket designed to hold a 387 compatible coprocessor in a 68-pin PGA. To get the best of both worlds, one might want to use a Weitek 3167 and a 387 compatible coprocessor in the same system. These coprocessors can coexist in the same system just fine. Only problem is that most 386 based systems contain only one coprocessor socket, usually of the EMC (extended math coprocessor) type. Thus, you can install either a 387 coprocessor or a Weitek 3167, but not both. There are little daughter boards available though that fit into the EMC socket and provide two sockets, an EMC and a standard coprocessor socket.
While support for 80x87 coprocessors is very common in application programs, the Weitek Abacus coprocessors do not enjoy such wide spread support. Due to their high price, only a few high-end PCs have been equipped with Weitek coprocessors. Therefore most of the programs that support these coprocessors are also high-end products like AutoCAD and Versacad-386.