Книга: Introduction to Microprocessors and Microcontrollers

Future development

The new Pentium design with speeds over 1.8 GHz and 0.13 µm technology is given the codename ‘Northwood’ that replaces the previous ‘Williamette’. The Williamette had reached the end of its development whereas the Northwood is just starting and since it is already running at 2.8 GHz, the magic 3 GHz chip is imminent, then we can probably look forward to the even more magic 4 GHz before the Northwood design is obsolete.

The Celeron

The bold type in computer adverts always shouts about ‘price and speed’ and many people fall into the trap of assuming that a 2.8 GHz microprocessor is obviously faster than a 2.5 GHz microprocessor. This is a false assumption but still well established so for this section of the market there is a demand for a very cheap microprocessor with a high clock speed.

The solution is to use the Pentium design and cheapen it by taking out some of the non-essential areas. There have been twelve such versions to track the Pentium releases during its development. In the 2 GHz Celeron, the price reduction has been achieved at the expense of reducing the L2 cache from 512 kB down to 128 kB and the FSB down from 533 MHz to 400 MHz.

Quiz time 12

In each case, choose the best option.

1 SIMD is:

(a) used in standard Pentiums but not in the MMX versions.

(b) a way of preventing wraparound.

(c) single in-line multimedia data.

(d) single instruction multiple data.

2 Branch prediction logic:

(a) is another name for the prefetch register.

(b) is only used in MMX versions.

(c) saves memory in 85% of occasions.

(d) attempts to guess the future steps to be taken by a program.

3 An exception:

(a) will be ignored if the I flag is set to a high level.

(b) is an unusual branching of the program.

(c) is an interrupt signal generated by the microprocessor.

(d) occurs whenever the Pentium is surprised by an arithmetic result.

4 The initials SIMD stand for:

(a) SIM card type D.

(b) Single Instruction Multiple Data.

(c) Superscalar Instruction Mode for Data.

(d) Streaming Instructions Modular Data.

5 In its construction, the Pentium 4 uses:

(a) 0.13 µm technology.

(b) 1.8 µm technology.

(c) 1.3 µm technology.

(d) 0.18 µm technology.

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