Fletcher's


The technical specifications of modern INTEL® processors.

( for Home and Business 'Desktop' systems.)


~ INTEL PRODUCTS ~
Standard Pentium \ Pentium Pro \ Pentium MMX \ Pentium II
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~ ARTICLES ~
Slots and Sockets \ Pentium II is a Pro ? \ Calculation of core frequencies \ Overdrive processor \ Backwards compatibility \ Clock multiplying \ Modes of operation
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~RELATED SITES~
Intel Secrets : No affiliation with Intel, many articles and info on motherboards and chipsets.
Chipsets and motherboards: Includes details of old and new chipsets, processors and motherboards.
Intel's Literature CentreFrom the horses mouth
DISCLAIMER


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Pentium ( family 'P5', 'P54C' )

Core Frequency Mhz I/O Core Voltage External Bus Frequency Trans -istors (million) Process micron
( µ )		 Bus / Core clock multiplic. ratio Data Bus Width Pin Grid Array (PGA) package
¹60 5 60 - 0.8 1 64 273
¹66 5 66 - 0.8 1 64 273
² 75 3.3 50 3.3 0.6 1.5 64 296
²90 3.3 60 3.3 0.6 1.5 64 296
²100 3.3 50/66 3.3 0.6 1.5/2.0 64 296
²120 3.3 60 3.3 0.35/0.6 2.0 64 296
²133 3.3 66 3.3 0.35 2.0 64 296
² 150 3.3 60 3.3 0.35 2.5 64 296
²166 3.3 66 3.3 0.35 2.5 64 296
² 200 3.3 66 3.3 0.35 3.0 64 296

8k data + 8k instruction level 1 cache

¹ = 'original' Pentium processor, code name 'P5'

² = BiCmos silicon technology, code name 'P54C', 75 - 200mhz processor 'family'.


Instead of calling it a '586', Intel gave their product a name for the legal requirements of a trademark. The first Pentium is characterised by a 16kb internal split cache, 8k for code and 8k for data, a 64 bit bus width both internally, and also externally, connecting with the motherboard. The Overdrive processor allowed allowed the use of existing 32 bit motherboards. Superscalar execution enables two instructions to be processed simultaneously, Branch Prediction is enabled by a small cache set aside to predict which way program logic will go and a redesigned Floating Point Unit ( called the co-processor ) with 5 times the performance of the 486 DX2 66. Visit the Intel site for more details of the architectural enhancements in the Pentium processor onwards.

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Pentium 'Pro' ( family 'P6')

150, (256k level2 cache) 3.3 60 5.5 0.32 2.5 64 296
166, (512k level2 cache) 3.3 66 5.5 0.32 2.5 64 296
180, (256k level2 cache) 3.3 60 5.5 0.32 3.0 64 296
200, (256 / 512k level2) 3.3 66 5.5 0.32 3.0 64 296

8k data + 8k instruction level 1 cache (total 16k)


The Pro is unique in that it contains two chips in a single package, the CPU proper and either 256 (0.6µ) or 512 (0.35µ, 3.1 million transistors) Kb of high speed Level 2 cache memory and uses the larger type 8 socket and so cannot be used to upgrade from plain Pentium class chips. There is a 16k Level 1 cache on all versions.

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Pentium MMX techn. (MultiMedia eXtensions)... 'P55C'

150 3.3 60 4.5 0.35 2.5 64 296
166 3.3 66 4.5 0.35 2.5 64 296
200 2.8 66 4.5 0.35 3.0 64 296
233 2.8 66 4.5 0.35 3.5 64 296

16k data + 16k instruction level 1 cache (total 32k)

Includes all the features of a standard Pentium, plus the ability to run software designed for MMX technology at a faster rate. The 32k internal cache (16k + 16k) makes even standard software run faster, more instructions / data can be stored on the chip, reducing the number of times the processor has to access slower, 'off chip' memory. The P166 MMX runs standard software faster than a P200 without MMX. What is MMX technology ?

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Pentium II ( 'Klamath', family 'P6' architecture)

SLOT 1
233 2.8 66 7.5 0.35 3.5 64 242
266 2.8 66 7.5 0.35 4.0 64 242
300 2.8 66 7.5 0.35 4.5 64 242

16k data + 16k instruction level1 cache, speed as core frequency, (total 32k) see note below




Pentium II (1998) and 'Deschutes' revision

SLOT 1
333 2.8 66/100 . 0.35 5.0 64 242
SLOT 2
350 1.8 100 . 0.25 3.5 64 242
450 1.8 100 . 0.25 4.5 64 242




Connections, Slots and Sockets

With the Pentium II, Intel has drastically changed the connection method of processor to motherboard. The packaging has changed and a 'processor card' which Intel calls 'Slot 1', the patented (proprietary) motherboard connector for the P IIs Single Edge Contact (SEC) cartridge. This replaces the Pin Grid Array (PGA) or 'Socket 7/8' package of all previous Pentium processors *. The Pentium Pro has a larger PGA and is termed 'Socket 8'. Slot 1 to Socket 8 adapters are made to allow for P. Pro processors to fit into slot 1, as the P. Pro cannot yet be seen to have reached the end of its life. Socket 7 is the 'de facto' industry standard (and still has plenty of mileage) design originated by Intel that can be used for any P54C or P55C processor, including the AMD K5/6 and the Cyrix/IBM 6x86 range. Socket 7 superseded socket 5/6 that earlier, single voltage processors used. Socket 4 was used by the 5 volt Pentium. Prior to this, socket standards were less well defined. SEE Clone Processors
.
* both Socket 7 and 8 are termed as ZIF sockets (Zero Insertion Force, i.e. enables a push fit upgrade).



Pentium II is a Pentium Pro ?

It could be argued that Intel's main reason for creating the Pentium II was to reduce the cost of manufacturing Pentium Pro class chips and also increase yields. Because the CPU core and Level 2 cache are both on the same chip in the Pro (users got performance gains as the Level 2 cache operates at the same speed as the core) the whole package can only be tested at the end of the manufacturing process. Any defects mean that both components must be discarded. Separating the Level 2 cache and packaging it in the SEC cartridge (Slot1) can also be seen as a strategy to keep competition ( like AMD and Cyrix (IBM) ) at bay by creating a new motherboard architecture, (Intel produce most of the motherboards ) as well as giving more flexibility to design and manufacturing. Pentium II processors are based on the Pentium Pro. They also include MMX technology ( now needed in business applications such as video conferencing as well as games ) and provide the fastest performance for both multimedia and business. Technically, Slot 1 offers the same functions as Socket 8 (P. Pro). Intel have removed the internal L2 cache the Pro had ( which lowers cost and makes more economical manufacture ). To make up this loss, the L1 cache is doubled to 32k. This helps reduce the disadvantage of an external L2 cache ( i.e off the CPU chip, running at half speed ). A separate level 2, 512Kb cache (larger for the new 'Deschutes' chip) and other components are mounted on the SEC, but separation from the main processor means a 'backside' bus is used to join the L2 cache and CPU. This runs at half clock speed. However 'Deschutes' ( a new 'slot 2' ) will run full speed. MMX is a standard feature in the Pentium II and will remain so from now on, but will eventually be replaced by MMX2. The main competitors, produce compatible equivalents. The Pentium II SEC measures 5.505" x 2.473" x0.647"

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Attempting to predict Intel's processor roadmap has always been a popular industry pastime, mainly due to the company's traditional reluctance to talk about future products in the public domain. However, Intel has 'opened up' slightly with a short term version of its roadmap on the Intel Developer Web site, the longer term details are still the subject of much speculation.




ARTICLES


       Real, Protected and Native (386 Enhanced) Modes.

These modes of operation help provide a degree of 'backwards compatibility', of a different sort to 'instruction set backwards compatibility' and are necessary because of issues of memory addressing.

A 286 could address 16 mb (in 64k chunks), but a 386 and greater (32 bit) processors have been able to address 4 gb (in one chunk.)

New processors released from Intel (or clone chip makers) can emulate the 'addressing' ability of a previous model if necessary ( to maintain compatibility with 'older' software which was written for the amount of addressable memory of the time.)

This is achieved by a switching between addressing 'modes' of operation. For example, simulation of the 'original' 8088 chip by an 80286 or greater CPU is achieved by 'REAL' mode (8088/86 compatibility, emulating the 1MB memory restriction).

A 286 in Protected mode allows 'protected' memory ranges to avoid program conflicts (for multitasking).

The 80386 introduced a new mode, as well as operating in real mode and protected mode it used Virtual 8086 mode

Virtual 8086 mode enables one or more 'virtual' real modes to be set up in protected memory, or put another way the 386 could emulate multiple 8086 chips, each in an isolated memory space. In this way, the 386 became the first practical multitasking chip in the Intel family, and enabled Windows to come of age.

The 286 was able to multitask protected mode programs, but the programs and operating systems of the time offered little support for this feature. It could run Windows, but not well.

An Operating System such as Win '95 can have more than one DOS 'window' operational. To further complicate matters, Windows 3.0/3.1 had the ability to run in 386 Enhanced mode or a Standard mode, the latter being developed for operation with a 80286 processor (ver. 3.11, Windows for Workgroups will only run in 386 Enhanced mode.) Many applications can determine what type of microprocessor is present and then install themselves to make the most of the features available

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       The 'Overdrive' Processor ( P24T, P54T. )

New models with incremental performance improvement going back to the x486, gave Intel a potential marketing nightmare, continuing technological advance meant faster and more powerful products were constantly emerging to both keep pace with competition and to meet market demand. However Intel turned the situation to their advantage by encouraging system designers to place a socket ('Power Up' or 'Overdrive' socket) on the motherboard such that a PC owner could upgrade by unplugging the processor and replacing it with a 'DX' or clock increased version. The PC would never be obsolete! Customer satisfaction! Intel were able to announce a version of the Pentium that would be compatible with x486 processor pin outs on machines that had been bought as 'Pentium ready', a misleading term enabling a 486 to Pentium upgrade - the Pentium Overdrive processor. However, to maintain compatibility with the existing 32 bit motherboard, the Overdrive does not have an 'external' 64 bit bus, creating a potential performance drop.

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       Backwards Compatibility

The original IBM PC was manufactured around the Intel 8088 microprocessor and since its introduction Intel and there competitors have provided a steam of new, higher specification processors as upgrades, even if the remainder of the system has received little or no enhancement of performance. However when Intel push new processor products they must ensure that the existing software base will function without modification.

Software is written to run on a specific microprocessor and Operating System. Customer investment in existing software must always be protected, although software itself goes through an upgrade process, progressing with processor upgrades and other system enhancements. Existing investment in software (direct and indirect) is too large to be neglected either by those who buy software or write software. The strategy of never rendering any PC software obsolete is a key marketing strength of the Intel architecture. New microprocessors, like any product improvement,

always contains extra features and performance enhancements which can be exploited by programmers when they provide upgrades to software or new software. New software may not work with older microprocessors, but older software will always work with new microprocessors. New software must be checked for compatibility before purchase if required to run on an older processor, but even the latest Intel and 'clone' processors can execute software written for the 17 year old 8088 device!

The application instruction set of the Pentium processor family includes the complete 486 set with 'extensions' to accommodate some of the additional functionality of a Pentium. However, software compiled specifically for a Pentium (MMX or not) may not be backwards compatible with a previous processor. Any new processor designs which cannot run the huge body of PC software will have a difficult time dethroning the Intel architecture.

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       Clock Multiplying

As chips have continued to shrink in size, the opportunity has arisen to run them internally at higher speeds, less heat dissipation from lower power consumption is a factor in this as has the increase in circuit logic occupying the same space. However externally, bus speed on the motherboard has remained stationary for a comparably long time although new standards will amend this soon, consequently the processor can still be subject to bottlenecks elsewhere in the system. A level1 cache design on the processor enabled clock multiplying without great modification to surrounding hardware. The internal speed is obtained by circuitry, which multiplies typical bus speeds of 50, 60 or 66 by a factor of 1, 1.5, 2.0, 2.5 or 3.0. The resulting core frequency in Mhz of a processor is a factor of the clock multiplication factor and the bus frequency, hence 3.0 x 66 = 198 ( which gets rounded by manufacturers to 200mhz for effect .)

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       Performance Indicators

There are industry standard benchmarks which give comparisons between processors of different makes. It should be remembered also that RAM size and type will affect performance even though this is external to the chip. Cache size advantage is considered as a part of the processor



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