tailieunhanh - Ebook The indispensable PC hardware book (3rd edition): Part 2

(BQ) Part 2 book "The indispensable PC hardware book" has contents: Graphics adapters, other interfaces, hard disk drives, floppies and floppy drives, floppies and floppy drives, other peripheral chips and components, multimedia,.and other contents. | 18 Our Mathematical Grandmother The MathCo 8087 The four basic arithmetical operations with integers are already integrated on the 8086/88. It is not surprising that the 8086/88 can handle neither floating-point numbers nor transcendental functions; this is carried out by the mathematical coprocessor 8087. It can enhance the performance up to a factor of 100, when compared to software emulations. Additionally, the 8087 supports an SOSS/SS CPU in maximum mode with 68 new mnemonics. 8087 Number Formats and Numerical Instruction Set As a mathematical coprocessor, the 8087 can process floating-point numbers directly. In the same way as the 80286 and its successors, the 8087 represents all numbers in the temporary real format according to the IEEE standard. Figure (Chapter 6) shows the number formats that are supported by the 8087. Unfortunately, the 8087 does not implement the IEEE standard for floating-point numbers in a very strict way (not very surprising - the 8087 was available before the standard). The 8087 numeric instruction set is slightly smaller than that for an i387 or 80287XL; for example, the FSETPM (set protected mode) instruction is (of course) missing. Further, no functions for evaluating sine and cosine are available. But they can be constructed with the help of the tangent. A detailed list of all 8087 instructions is given in Appendix Cl. 8087 Pins and Signals Like the 8086/88, the 8087 has 40 pins in all for inputting and outputting signals and supply voltages. Usually, the 8087 comes in a 40-pin DIP package. Figure shows the pin assignment of the 8087. ADlS-ADO (I/O) Pins 39, 2-16 These 16 connections form the 16 data bits when the 8087 is reading or writing data, as well as the lower 16 address bits for addressing memory. As is the case with the 8086, these 16 pins form a time-divisionally multiplexed address and data bus. A19-A16/S6-S3 (II01 Pins 35-38 These four pins form the four high-order bits of the address bus, as well