P5 (microarchitecture)

  • Base 4
  • Base 5
  • Socket 7
  • P5
  • P54
  • P54CS
  • P55C
  • Tillamook

The Pentium is a site presented by Intel 1993 processor (CPU). He was the successor of the i486 CPU series from the same home. When the Pentium was announced, expected the professional world with a continuation of the formerly standard naming scheme for x86 processors. Accordingly, the CPU should have 80586 or shortly i586 hot. End of 1992, Intel had but then announced that the time for CeBIT 1993 announced CPU should bear the name Pentium. Pente ( πέντε ) - the Greek word for five - should now enter the name of the fifth -generation x86 from Intel.

Intel justified this step with the impossibility to obtain protection under trademark law numbers. In the i486 processors Intel had experienced what it can mean when the competition such as Cyrix must use the same name as the original.

One of the main architects was John Crawford.

The Pentium processor family

Pentium should then not only the fifth but the sixth and seventh generation x86 hot from Intel. Today an entire processor dynasty that name. The Pentium followed the Pentium Pro, Pentium II, Pentium III, Pentium 4, Pentium M, Pentium D and the Intel Pentium Dual-Core. Although these processors except the instruction set have little in common with the first Pentium, they bear his name.

Many people of the name Pentium was therefore used synonymously with the current Pentium processor, which makes a conceptual distinction from the original Pentium sometimes not easy. For this reason, Pentium family has later also the name Pentium 1 naturalized, although Intel has never called him so for the first one.

The Pentium -1 family

On the right you can see a typical representative of all three types of Pentium -1 family, some with different housing variants. In the center is a Pentium 60 (P5 ), above a Pentium 166 ( P54CS ). Clockwise a Pentium follow 120 ( P54C ), a Pentium MMX 233 ( P55C ), then a Pentium 75 ( P54C ) in the ceramic version, a Pentium 90 ( P54C ) with integrated heat sink and finally a Pentium MMX 166 ( P55C ).


1 all Pentium processors based on the core of the Pentium-60/66, designated as Intel internally P5. Nevertheless, it has P5- family - in contrast to the P6 family - never naturalized as a name for the Pentium -1 family. Unlike, for example, the Pentium Pro, the Pentium by the same developer team, which had already developed the 486 comes from.

The Pentium was the first superscalar CISC microprocessor in the world. Man this integrated RISC technology without losing backward compatibility to 486. From the 486 to the Pentium, the biggest technical change took place in the history of the 8086 line.

Already the 486 led simple commands in a kind of pipeline. Unlike the Pentium its pipeline stages but were rather sent interconnected functional groups, as they already knew from 386. Thus, the instruction fetch could ( instruction fetching, fetch), the instruction decode ( decode ) and indeed run the command execution ( execute) largely parallel, but it was not possible to better utilize the functional units involved in the instruction execution, by allowing it to simply work in parallel, when the command sequence allowed.

This should change the Pentium. He owned two integer pipelines, one floating point pipeline, dynamic branch prediction, separate data and code caches with a size of 8KB and a 64 -bit wide external data bus with fast burst modes to connect the external cache quickly. There were also additional features such as a system management mode ( SMM), hardware- supported performance monitoring and execution tracing. The two pipelines that allow the Pentium to have two involved in the instruction execution functional units working in parallel, if there is the possibility (integer and floating-point operations can be performed largely independently of each other ). The dynamic branch prediction compensates for a conceptual drawback of the pipeline architecture: If a jump occurs, the results already part of processed commands are invalid and therefore the complete contents of the pipeline must be discarded (so-called pipeline flush). The address bus was 32 ​​bits wide (4 GiB address space), which is far enough at this time, since the chipsets caching permitted only in a small part of the address space.

The FDIV bug

Only one and a half years after his performance made ​​the Pentium with a spectacular design flaw stir. The FDIV bug - sometimes also referred to merely as something unspecific Pentium bug due to its popularity - shook the confidence of many users in the fledgling Pentium family.

Variants of Pentium -1

The P5 Pentium

The first generation of Pentium, P5, was presented at the CeBIT 1993. The only two representatives of the P5 Pentium, the Pentium 60 and 66 Both operate with a supply voltage of about 5 volts and are not multiprocessing capable by default. But you already support the MESI protocol to ensure cache coherency in multiprocessor mode. Your core is - comparable to the first 486 processors - still operate at the same clock frequency as the bus interface. Both CPUs only fit into the socket 4 and differ only slightly from their otherwise functional successor, the P54C.

Despite his advanced designs of the P5 was not a great success for Intel. But that was not attributable to a lack of technical skills; rather, Intel had created an in-house competitor, the clocked with 100 MHz processor i486 DX4. Complete systems with the DX4 were significantly cheaper to purchase and were at least those with a Pentium 60 in terms of computing power hardly after. In addition, the DX4 could be upgraded if a 486 motherboard was already present, which did not provide good starting conditions for the new processor.

Another problem is the power supply voltage of about 5 volts. In conjunction with the then often just dimensioned heat sinks (which were at the time of introduction of the Pentium is not always required and therefore spread a little) and fans, this leads to a strong heating of the CPU, and often adjacent components on the motherboard (heat conduction through the conductors made of copper ), which usually leads to unstable operation of the computer.

The P54C Pentium

The P54C Pentium, which is also referred to as Pentium -S, was introduced at CeBIT 1994. He came first with 90 and 100 MHz and shortly thereafter with 75 MHz on the market. By the year 1997 yet was followed by versions with 120, 133, 150, 166 and 200 MHz. In contrast to P5 of the P54C has an onchip APIC and is thus innately multiprocessing capability. Nevertheless guaranteed Intel not who do not support the multi-processor operating at any CPUs for the function of the APIC, which is why versions sold. In addition, the P54C has improved, so-called SL -enhanced power management. For the first P54C was the base 5 and later also provided the base 7. The supply voltage was reduced to 3.3V.

Unlike its predecessor, the P5, the P54C was a great success for Intel. It took almost two years to competitive Pentium clones came on the market. The 486 platform initially further from - While Intel Pentium favored, slaughtered the competition - also successful. So AMD and Cyrix brought further fast 486 processors on the market in late 1995 - under the name 5x86 - even those that could take up to a Pentium 75, it is quite. At that time, Intel was already but the Pentium 133 In the course of 1996, AMD countered with the 5k86, later K5 and Cyrix with the 6x86. The latter even managed the then fastest Pentium to be dangerous with the integer processing power. But before the 6x86 able to establish itself properly, in turn countered Intel in early 1997 with a further development of the P54C, P55C the.

The P55C Pentium (Pentium MMX)

The P55C was developed in Intel's research and development center in Haifa ( Israel). He is the last and most powerful processor from the Pentium -1 family. The sale was made under the name Pentium MMX, since it is equipped as a first processor with Intel's new MMX instruction set extension. The Pentium MMX is available with clock frequencies 133-300 MHz, stay with 133, 266 and 300 MHz, the mobile variant reserved. Since CPU core and bus interface operating at P55C with different voltages, it requires a special form of Socket 7, the so-called split- Voltage -enabled Socket 7, not to be confused with the Super Socket 7

In addition, the P55C has been greatly improved internally. Although he retained essentially the architecture of the P54C in, but optimized and supplemented them in many places. Thus, the P55C has twice as much cache as its predecessors, has significantly improved - inherited from the Pentium Pro - branch prediction, four instead of two write - buffer and an internal CPU return stack to accelerate subroutine return jumps. His pipelines have been improved. So they can now be loaded in parallel using command combinations ( so-called command pairings ) that were previously not possible, and an additional step has been added.

Although the improvements on the pipeline was made ​​mainly because of the enlargement to the MMX instructions, even non- MMX applications benefit from it. Bottom line, the improvements in a significant performance increase noticeable. The P55C is for non- MMX applications on average about 15 to 20 percent faster than an equally clocked P54C, with a large part of this increase is attributable to the larger cache.

As PentiumODPMT ( P54CTB, P5 - OverDrive processor ) there were versions of the P5- MMX, which is also on motherboards with Socket 5, ie without shared power supply, were used due to an integrated voltage converter.

Model Overview

* These are only available as a Mobile Pentium or Pentium MMX Mobile for laptops. ** Not TDP, but Max Active Power Dissipation Intel *** SmartDie 27315402 (or 273154-002 ) Mobile Pentium ® Processor MMX ™ Technology Micron 0:25 SmartDie ® Product Specification

More Pentium models


Intel data sheets:

  • Pentium (P5 ): http://datasheets.chipdb.org/Intel/x86/Pentium/24159502.pdf
  • Pentium ( P54C ): http://datasheets.chipdb.org/Intel/x86/Pentium/24199710.PDF
  • Pentium MMX ( P55C ): http://datasheets.chipdb.org/Intel/x86/Pentium % 20MMX/24318504.PDF
  • Mobile Pentium MMX ( P55C ): http://datasheets.chipdb.org/Intel/x86/Pentium % 20MMX/24329204.PDF
  • Mobile Pentium MMX ( Tillamook ): http://datasheets.chipdb.org/Intel/x86/Pentium % 20MMX/24346802.PDF
  • Mobile Pentium ® Processor with MMX ™ Technology (0.25 Micron Process) Intel ® SmartDie Product Specification: http://datasheets.chipdb.org/Intel/x86/Pentium % 20MMX/27315402.PDF