PENTIUM II / 440LX

THE 440LX CHIPSET

Intel Pentium II ("Klamath")

Codenamed for the Oregon river "Klamath", Intel officially released the Pentium II in May of 1997. The Pentium II improves over the Pentium Pro architecturally in the following areas (many of these having been done to compensate in part for the reduced speed of the Pentium II level 2 cache compared to the Pentium Pro):

Doubled Level 1 Cache:

The level 1 cache is increased in size from 16 KB to 32 KB total (16 KB + 16 KB).

Segment Register Caches:

These are special caches that are used to help the Pentium II process 16-bit code somewhat more efficiently. The Pentium Pro was optimized for 32-bit processing, meaning that it did not deal with 16-bit code quite as well. Probably in response to the dominance of the Windows 95 operating system (which still uses a lot of 16-bit code) there was a desire to improve performance in this respect.

Deeper Write Buffers:

The write buffers were increased in size, producing a small performance improvement.

Without a doubt, the most talked about aspect of the new Pentium II wasn't even the chip itself--it was how it was packaged. The integrated Pentium Pro secondary cache, running at full processor speed, was one of its great performance-enhancing features--a "fan favorite" if you will. Intel replaced this on the Pentium II with a special small circuit board containing the processor and 512 KB of secondary cache, running at half the processor's speed. This assembly, termed a single-edge cartridge (SEC), was designed to fit into a 242-pin slot on the Pentium II motherboard. This change of design led to quite a bit of controversy in several regards!

The newest packaging style for desktop PCs, Single Edge Contact or SEC, is a move away from the single-chip-style packaging that Intel has used for all of its processors up to the Pentium Pro. The PPro had integrated secondary cache, inside the same chip package with the chip itself. With the creation of the Pentium II processor, Intel moved the secondary cache off-chip, but wanted to be able to maintain a special high-speed connection between it and the actual processor. To do this, they decided to not sell the Pentium II as a separate chip, but rather as an integrated package with the level 2 cache. SEC was the result.

The SEC is actually a daughtercard, not a chip package at all. The processor itself is packaged using technology similar to regular PGA, but is mounted onto a small circuit board with a proprietary connector on its edge. The level 2 cache is also mounted onto this daughtercard, which goes into a special slot on the motherboard. This allows for a higher-speed interface to the secondary cache, since it is not on the motherboard as it is with the Pentium and Pentium with MMX motherboards. It also allows Intel to create a patented, proprietary motherboard interface for its new CPUs, which caused a fair bit of commotion at its introduction.

The decision to "downgrade" the secondary cache from processor-speed to half-processor-speed led to some criticism of Intel, as this was viewed as a step backwards by many. There is a new P II (Slot 2) to be released with full processor speed. The P II board provides 66 MHz memory bus speed, 4.5 processor clock multiplier, and 2.8 internal voltage.

General Information

Manufacturer

Intel

Family Name

Pentium II

Code name

"Klamath"

Processor Generation

Sixth

Motherboard Generation

Sixth

Version

Pentium II 233

Pentium II 266

Pentium II 300

Introduced

May 1997

Variants and Licensed Equivalents

--

Speed Specifications

Memory Bus Speed (MHz)

66

Processor Clock Multiplier

3.5

4.0

4.5

Processor Speed (MHz)

233

266

300

"P" Rating

--

Benchmarks

iCOMP Rating

--

iCOMP 2.0 Rating

267

303

332

Norton SI

--

Norton SI32

~115

~130

!?

CPUmark32

~640

~700

!?

Physical Characteristics

Process Technology

CMOS

Circuit Size (microns)

0.35

Die Size (mm^2)

203

Transistors (millions)

7.5

Voltage, Power and Cooling

External or I/O Voltage (V)

3.3

Internal or Core Voltage (V)

2.8

Power Management

SMM

Cooling Requirements

Active heat sink

Packaging

Packaging Style

242-Pin SEC

Motherboard Interface

Slot 1

External Architecture

Data Bus Width (bits)

64

Maximum Data Bus Bandwidth (Mbytes/sec)

533

Address Bus Width (bits)

36

Maximum Addressable Memory

64 GB

Level 2 Cache Type

SEC, non-blocking

Level 2 Cache Size

512 KB

Level 2 Cache Bus Speed

116 MHz

133 MHz

150 MHz

Multiprocessing

Dual (SMP) with compatible motherboard

Internal Architecture

Instruction Set

x86 plus Pentium and Pentium Pro extensions

MMX Support

Yes

Processor Modes

Real, Protected, Virtual Real

x86 Execution Method

x86 Emulation

Internal Components

Register Size (bits)

32

Pipeline Depth (stages)

14?

Level 1 Cache Size

16 KB Data, 16 KB Instruction

Level 1 Cache Mapping

2-Way Set Associative

Level 1 Cache Write Policy

Write-Through, Write-Back

Integer Units

5? (1 for MMX)

Floating Point Unit / Math Coprocessor

Integrated

Instruction Decoders

1 Sophisticated, 2 Simple

Branch Prediction Buffer Size / Accuracy

512 entries / 90%

Write Buffers

!?

Performance Enhancing Features

Out of Order Execution, Speculative Execution, Register Renaming, Superpipelining, Segment Register Caches

Intel 440LX

The 440LX is Intel's latest and current top-end chipset, designed specifically for their latest and current top-end processor, the Pentium II. The Pentium II was released several months before the 440LX was ready, and so early PII motherboards used the older 440FX chipset. This chipset was never designed with the Pentium II in mind of course, and the 440LX was, optimized specifically to take advantage of its architecture.

Compared to the 440FX, the 440LX chipset offers several improvements. The key ones are:

Of course, the 440LX is used in the latest and best Pentium II motherboards, and supports the SEC packaging used by that processor.

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