Intel387TMDX

Case Temperature T_C
    Under Bias ...........-65°C to +110°C
Storage Temperature .......-65°C to +150°C
Voltage on Any Pin with
    Respect to Ground .......-0.5 to V_CC +0.5V
Power Dissipation................1.5W

The Intel387^TM DX Math Coprocessor provides arithmetic instructions for a variety of numeric data types in Intel386TM DX Microprocessor systems. It also executes numerous built-in transcendental functions (e.g. tangent, sine, cosine, and log functions). The Intel387 DX MCP effectively extends the register and instruction set of a Intel386 DX Microprocessor system for existing data types and adds several new data types as well. Figure 1.1 shows the model of registers visible to programs. Essentially, the Intel387 DX MCP can be treated as an additional resource or an extension to the Intel386 DX Microprocessor. The Intel386 DX Microprocessor together with a Intel387 DX MCP can be used as a single unified system.

The Intel387 DX MCP works the same whether the Intel386 DX Microprocessor is executing in real-address mode, protected mode, or virtual-8086 mode. All memory access is handled by the Intel386 DX Microprocessor; the Intel387 DX MCP merely operates on instructions and values passed to it by the Intel386 DX Microprocessor. Therefore, the Intel387 DX MCP is not sensitive to the processing mode of the Intel386 DX Microprocessor.

In real-address mode and virtual-8086 mode, the Intel386 DX Microprocessor and Intel387 DX MCP are completely upward compatible with software for 8086/8087, 80286/80287 real-address mode, and Intel386 DX Microprocessor and 80287 Coprocessor real-address mode systems.

In protected mode, the Intel386 DX Microprocessor and Intel387 DX MCP are completely upward compatible with software for 80286/80287 protected mode, and Intel386 DX Microprocessor and 80287Coprocessor protected mode systems.

The only differences of operation that may appear when 8086/8087 programs are ported to a protected- mode Intel386 DX Microprocessor and Intel387 DX MCP system (not using virtual-8086 mode), is in the format of operands for the administrative instructions FLDENV, FSTENV, FRSTOR and FSAVE. These instructions are normally used only by exception handlers and operating systems, not by applications programs.

The Intel387 DX MCP contains three functional units that can operate in parallel to increase system performance. The Intel386 DX Microprocessor can be transferring commands and data to the MCP bus control logic for the next instruction while the MCP floating-point unit is performing the current numeric instruction.