Digital Electronics: Principles, Devices and Applications

Microprocessors 5572. The real address mode (also called the ‘real mode’) emulates the programming environment ofthe 8086 processor, with a few extensions (such as the ability to break out of this mode). Resetinitialization places the processor into real mode.3. The virtual 8086 mode (also called the ‘V86 mode’) is another form of 8086 emulation mode. Unlikethe real address mode, virtual 8086 mode is compatible with protection and memory management.The processor can enter virtual 8086 mode from protected mode to run a program written for the8086 processor, then leave virtual 8086 mode and re-enter protected mode to run programs that usethe 32-bit instruction set.13.11.5 PowerPC RISC MicroprocessorsThe PowerPC family of microprocessors are high-performance superscalar RISC microprocessorsdeveloped jointly by MOTOROLA, IBM and Apple. They are used in personal computers, workstationsand servers as well as for industrial and commercial embedded applications. Different versions ofPowerPC microprocessors include PowerPC 601, 602, 603, ec603e, 604, 604e, 620, 740, 750, 745,755, 750CX, 750CXE, 750FX and 750X microprocessors. PowerPC 601, 602, 603, ec603e and 604 are32-bit microprocessors with a 32-bit address bus and a 64-bit data bus. They have 32 32-bit generalpurposeregisters and 32 64-bit floating-point registers. PowerPC 601 was introduced in the year 1993for desktop PCs and low-end workstation applications. It uses 0.5 m process technology and isavailable in 100 and 120 MHz clock frequency versions. PowerPC 602 was designed for graphical andmultimedia applications. PowerPC 603 was introduced in the year 1993 and was used for applicationswhere low power consumption was a critical requirement. It operates at 100 MHz. Its version 603eis an embedded microprocessor operating at 300 MHz. PowerPC 604 introduced in the year 1994 isavailable in different versions operating at 80, 100, 120, 133 and 250 MHz.PowerPC 740/750 are 32-bit RISC microprocessors with special added features including afaster memory bus (66 MHz), larger L1 caches, enhanced integer and floating-point units andhigher core frequency. PowerPC 750CX was developed by IBM using an 0.18 m copper process.PowerPC 750FX was introduced in the year 2002 and had an operational frequency of up to 900MHz. PowerPC 750GX introduced in the year 2004 is the latest and most powerful G3 processorfrom IBM.13.12 Pentium Series of MicroprocessorsThe Pentium family of processors has its roots in the Intel 486 processor and has the same instructionset with a few additional instructions. Pentium processors have a 64-bit data bus and represent a majorstep forward in personal computer CPU design. The first Pentium processors (the P5 variety) wereintroduced in 1993. They were fabricated in 0.8 m bipolar complementary metal oxide semiconductor(BiCMOS) technology. The P5 processor runs at a clock frequency of either 60 or 66 MHz and has3.1 million transistors. The next version of the Pentium processor family was the P54 processor. TheP54 processors were fabricated in 0.6 m BiCMOS technology. The P54 was followed by P54C,introduced in 1994, which used a 0.35 m CMOS process, as opposed to the bipolar CMOS processused for the earlier Pentiums. The P5 operated on 5 V supply and the P54 and P54C series operatedon a 3.5 V supply voltage. All these processors had a problem in the floating-point unit. They werefollowed by the P55C processor, also referred to as the Pentium MMX. It was based on the P5 coreand fabricated using the 0.35 m process. The performance of the P55C was improved over theprevious versions by doubling the level 1 CPU cache from 16 to 32 kB. Intel has retained the Pentiumtrademark for naming later generations of processor architectures, which are internally quite different