SUMMARY
1. The Pentium II differs from earlier microprocessors because instead of being offered as an integrated circuit, the Pentium II is available on a plug-in cartridge or printed circuit board.
2. The level 2 cache for the Pentium II is mounted inside of the cartridge, except for the Celeron, which has no level 2 cache. The cache speed is one half the Pentium II clock speed, except in the Xeon, where it is at the same speed as the Pentium II. All versions of the Pentium II contain an internal level 1 cache that stores 32K bytes of data.
3. The Pentium II is the first Intel microprocessor that is controlled from an external bus con- troller. Unlike earlier versions of the microprocessor, which issued read and write signals, the Pentium II is ordered to read or write information by an external bus controller.
4. The Pentium II operates at clock frequencies from 233 MHz to 450 MHz with bus speeds of 66 MHz or 100 MHz. The level 2 cache can be 512K, 1M, or 2M bytes in size. The Pentium II contains a 64-bit data bus and a 36-bit address bus that allow up to 64G bytes of memory to be accessed.
5. The new instructions added to the Pentium II are SYSENTER, SYSEXIT, FXSAVE, and FXRSTOR.
6. The SYSENTER and SYSEXIT commands are optimized to access the operating system in privilege level 0 from a privilege level 3 access. These instructions operate at a much higher speed than a task switch or even a call and return combination.
7. The FXSAVE and FXRSTOR instructions are optimized to properly store the state of both the MMX technology unit and the floating-point coprocessor.
8. The Pentium III microprocessor is an extension of the Pentium Pro architecture with the addition of the SIMD instruction set that uses the XMM registers.
THE PENTIUM II, PENTIUM III, PENTIUM 4, AND CORE2 MICROPROCESSORS 783
9. The Pentium 4 and Core2 microprocessors are extensions of the Pentium Pro architecture, which includes enhancements that allow it to operate at higher clock frequencies than previ- ously possible because of the 0.13 micron and the latest 45 nm fabrication technologies.
10. The Pentium 4 and Core2 microprocessors require a modified ATX power supply and case to function properly in a system.
11. Version 6.15 of the MASM program and Visual Studio version 6 now support the new MMX and SIMD instructions using the .686 switch with the .MMX and .XMM switches.
12. The Pentium II, Pentium III, Pentium 4, and Core2 microprocessors are all variations of the Pentium Pro microprocessor.
13. Future Pentium 4 and Core2 microprocessors will all use the 64-bit extension to the 32-bit architecture. This will become important in systems with more than 4G bytes of memory.