CertiGuide to A+ (Core Hardware)  9  Chapter 0010:  CPUs       9  V  Pentium Family CPUs

V  Pentium Family CPUs 1 Pentium MMX

The original Pentium was out (introduced) at 60MHz, and was later upped to 66Mhz. While the Pentium rocked the digital world, it did have one challenge. Operating at five volts, the CPU put out tremendous heat, limiting the ability to create even faster processors. The 66 MHz Pentium consumed a whopping 16 W of power (3.2 Amps). This made laptop computers fry legs of the laps they sat on. The solution was simple, as soon as it was technically feasible. Lower the required voltage. And lowering the voltage to about 3.3 volts exactly what Intel did, starting with the 75Mhz Pentium. Actually, the 75Mhz Pentium used 3.465 volts, but you get the idea.

Intel worked on getting the requirements down, and labeled each Pentium with a suffix:

• Standard (STD): 3.30V
  
  
• Voltage Reduced (VR): 3.38V
  
  
• VR Extended (VRE): 3.50V

Voltage ‘standards’ begin to get confusing with later Pentiums, all Pentium Overdrive CPUs, and settles to 3.3Volts and 2.8Volts at the core of the CPU through the PII.

To make sure the newer Pentium using the lower voltage was not inadvertently plugged into a system board using five volts Intel changed the socket type (Socket 4) to a 296-pin arrangement and staggered the pinouts to create the Staggered Pin Grid Array (SPGA).

Another feature of the second-generation offering was the Advanced Programmable Interrupt Controller (APIC) that in concert with a dual-processor interface allowed system board makers to create systems holding multiple CPUs. This really helps out some Operating Systems, such as NT handling larger loads. When multiple-processors are used the process is known as Symmetric Multi-Processing (SMP).

Another issue facing the Intel engineers was the fact that they were able to get CPU speeds moving along faster than the rest of the system bus could handle. The solution was to use a clock-multiplier circuit to run the processor at speeds faster than the rest of the system. Table 10 shows a typical multiplier and system board speed.

V  Pentium Family CPUs 1 Pentium MMX