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close this bookNew Training Technologies (ILO - UNEVOC, 1995, 95 p.)
close this folderAppendix A Compatibility
View the document(introduction...)
View the documentPC buses (architecture)
View the documentMicroprocessors
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Microprocessors

The engine of a PC is its microprocessor. Several manufacturers are producing them; INTEL is currently equipping most of the IBM and compatible PCs:

· the very first PCs were equipped with 8088 microprocessors, sending and receiving 8-bit data;

· the 8086 came later, sending and receiving 16-bit data;

· the 80286 is also a 16-bit data microprocessor, which can work in two modes: the "real mode" used with DOS based applications, and the "protected mode" used with software which allows parallel processing of different applications (e.g. the OS/2 of IBM). When in real mode, the 80286 may address 1 Mb of memory, and when in protected mode, 16 Mb. To run a program like WINDOWS, a 80286 is a minimum configuration;

· the 80386 is a 32-bit data microprocessor, offering extended memory processing functions. A simplified version (80386SX) only uses 16-bit data for the bus, and 32-bit for the other functions;

· the 80486 is a 32-bit data microprocessor, with a built-in arithmetic co-processor, which takes over a certain number of tasks from the microprocessor itself. It offers much more powerful memory management functions than the 80386; a 80486SX version does not have the built-in mathematical coprocessor, for those who do not have intensive computing applications. The so-called DX2 microprocessors double the internal clock frequency of the 80486, but they cannot be installed on all mother boards (on a 80486SX one has to install an "overdrive" on the arithmetic co-processor support, which plays the same role);

· the Pentium has been recently introduced on the market; it is a 32-bit microprocessor. It has RISC (Reduced Instructions Set Computer) characteristics, as opposed to the usual CISC (Complex Instructions Set Computer). The data bus is a 64-bit bus; it has two different 8 Kb cache memories and works at very high frequencies (60 or 66 MHz). It is one of the most powerful computing microprocessors in use at the moment;

· the Power PC microprocessor is the very first result of the work done in collaboration between APPLE, IBM and MOTOROLA. It equips recently announced PCs (e.g. Power Mac of APPLE, Enterprise Desktop of HP) which process all kinds of operating systems (APPLE, IBM, MICROSOFT, UNIX) and all kinds of application programs (IBM compatible, WINDOWS, APPLE); this is a remarkable advancement towards compatibility!

MOTOROLA microprocessors equip the APPLE and the ATARI computers:

· the 68000 model works with 16 bits;
· the 68020 model is a 32-bit one working at 12 to 25 MHz;
· the 68030 model is an improved 32-bit microprocessor;
· the 68040 model is a faster and more powerful 32-bit microprocessor.