Pentium III

Pentium III logo

Pentium III-M Logo

The Pentium III brand refers to Intel's 32-bit x86 desktop and mobile microprocessors (with the sixth-generation Intel P6 microarchitecture) introduced on February 26, 1999 and containing 9.5 million transistors. The brand's initial processors were very similar to the earlier CPUs branded Pentium II. The most notable difference was the addition of the SSE instruction set (to accelerate media processing and 3D graphics), and the introduction of a controversial serial number embedded in the chip during the manufacturing process.

Similarly to the Pentium II it superseded, the Pentium III was also accompanied by the Celeron brand for lower-end CPU versions, and the Xeon for high-end (server and workstation) derivatives. The Pentium III was eventually superseded by the Pentium 4, but its Tualatin core also served as the basis for the Pentium M CPUs, which used many ideas from the Intel P6 microarchitecture. Subsequently, it was the P-M microarchitecture of Pentium M branded CPUs, and not the NetBurst found in Pentium 4 processors, that formed the basis for Intel's energy-efficient Intel Core microarchitecture of CPUs branded Core 2, Pentium Dual-Core, Celeron (Core), and Xeon.

The Pentium III was the first Intel processor to break 1 GFLOPS, with a theoretical performance of 2 GFLOPS.

Pentium III cores

Katmai

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An Early Intel Pentium III Katmai Engineering Sample which is still labelled as a Pentium II.

The original version, Katmai (Intel product code 80525), was very similar to the Pentium II (using a 0.25 µm fabrication process), the only differences being the introduction of SSE, and an improved L1 cache controller (which was the cause of the minor performance improvements over the latter PIIs). It was first released at speeds of 450 and 500 MHz. Two more versions were released: 550 MHz on May 17, 1999 and 600 MHz on August 2, 1999. On September 27, 1999 Intel released the 533B and 600B running with 533/600 MHz but using a 133 MHz FSB, all others use a 100 MHz FSB.

The Katmai used the same slot based design as the Pentium II but with the newer SECC2 cartridge that allowed direct CPU core contact with the heatsink. There've been some early models of the Pentium III with 450 and 500 MHZ with SECC cartridge being delivered for OEM-use only.

A notable stepping for enthusiasts was SL35D. This version of Katmai was officially rated for 450 MHz, but often contained cache chips for the 600 MHz model and thus usually was capable of running at 600 MHz.

Coppermine

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A Pentium III Katmai SECC2 cartridge with Heatsink Removed

The second version, Coppermine, or 80526, had an integrated full-speed 256-bit 256 KiB L2 cache with lower latency, named Advanced Transfer Cache by Intel, which improved performance significantly over Katmai. Under competitive pressure from AMD’s Athlon processor, Intel also re-worked the chip internally, and finally fixed the well known instruction pipeline stalls. The result was a remarkable 30% increased performance in some applications where these stalls happened.

It was built on a 0.18 μm process. Pentium III Coppermines running at 500, 533, 550, 600, 650, 667, 700, and 733 MHz were first released on October 25, 1999. From December 1999 to May 2000, Intel released Pentium IIIs running at speeds of 750, 800, 850, 866, 900, 933 and 1000 MHz (1 GHz). Both 100 MHz FSB and 133 MHz FSB models were made. An "E" was appended to the model name to indicate cores using the new .18 micron fabrication process. An additional "B" was later appended to designate 133Mhz FSB models, resulting in an "EB" suffix.

A 1.13 GHz version was released in mid-2000 but famously recalled after a collaboration between HardOCP and Tom's Hardware discovered various instabilities with the operation of the new CPU speed grade. The Coppermine core was unable to reliably reach the 1.13 GHz speed without various tweaks to the processor's microcode, aggressive cooling, additional voltage (1.75 V vs. 1.65 V), and specifically validated platforms. Intel only officially supported the processor on its own VC820 i820-based motherboard, but even this motherboard displayed instability in the independent tests of the hardware review sites. In benchmarks that were stable, performance was shown to be sub-par, with the 1.13 GHz CPU equalling a 1.0 GHz model. Tom's Hardware attributed this performance deficit to relaxed tuning of the CPU and motherboard to improve stability. Intel needed at least six months to resolve the problems using a new cD0 stepping and re-released 1.1 GHz and 1.13 GHz versions in 2001.

A common misconception is that a modified version of the Coppermine was developed for Microsoft's Xbox game console. The Xbox does not actually use a Pentium III processor per se. It runs a Mobile Celeron 733 (Coppermine-128) in a Micro-PGA2 package. Given the fact that the Mobile Celeron 733 has the same 8-way associative cache used in Pentium III chips, it isn't a stretch to just call the Xbox CPU a "Pentium III with half the cache." Still, that statement isn't entirely correct.

Although the codename Coppermine makes it sound as if the chip was fabricated with copper interconnects, Coppermine in fact used aluminum interconnects.

Later in Coppermine's life, Intel implemented a heatspreader to improve contact between the CPU and the heatsink. The heatspreader itself didn't improve thermal conductivity, since it added another layer of metal and thermal paste between the CPU and the heatsink. But it greatly assisted in holding the heatsink flat against the CPU. Earlier Coppermine CPUs with bare cores made for challenging heatsink mounting. If the heatsink was not flat against the core, heat transfer efficiency was crippled. Some heatsink makers also began using pads on their coolers, similar to what AMD did with the "Thunderbird" Athlon. The enthusiast community went so far as to create shims to assist in maintaining a flat interface.

Coppermine-T

This core was an intermediate step between Coppermine and Tualatin, with support for lower-voltage system logic present on the latter but core power within previously defined voltage specs of the former so it could work in older system boards.

Intel used the latest generation Coppermines with cD0-Stepping and modified them so that they worked with low voltage system bus operation (GTL) at 1.25 V AGTL as well as normal 1.5 V AGTL+ signal levels, and would auto detect differential or single-ended clocking. This modification made them compatible to the latest generation Socket-370 boards supporting CPU in FC-PGA2 packages while maintaining combatility to the older FC-PGA boards. The Coppermine-T was also Dual-Processing capable but only in FC-PGA2 boards.

The Coppermine-T is the only Coppermine to feature an integrated Heatspreader.

Tualatin

The third revision, Tualatin (80530), was a trial for Intel's new 0.13 µm process. Pentium III Tualatins were released during 2001 until early 2002 at speeds of 1.0, 1.13, 1.2, 1.26, 1.33 and 1.4 GHz. Tualatin performed quite well, especially in variations which had 512 KiB L2 cache (called the Pentium III-S). The Pentium III-S variant was mainly intended for servers, especially those where power consumption mattered, i.e., thin blade servers.

The Tualatin also formed the basis for the highly popular Pentium III-M mobile processor, which became Intel's front-line mobile chip (the Pentium 4 drew a lot more power, and so was not well-suited for this role) for the next two years. The chip offered a good balance between power consumption and performance, thus finding a place in both performance notebooks and the "thin and light" category.

Tualatin-based Pentium III CPUs can usually be visually distinguished from Coppermine-based processors by the metal integrated heat-spreader (IHS) fixed on top of the package. However, the very last models of Coppermine Pentium IIIs also featured the IHS — the heatspreader is actually what distinguishes the FC-PGA2 package from the FC-PGA — both are for Socket 370 motherboards.

Before the addition of the heatspreader, it was sometimes difficult to install a heatsink on a Pentium III. One had to be careful to not put force on the core at an angle because doing so would cause the edges and corners of the core to crack and could destroy the CPU. It was also sometimes difficult to achieve a flat mating of the CPU and heatsink surfaces, a factor of critical importance to good heat transfer. This became increasingly challenging with the socket 370 CPUs, compared with their Slot 1 predecessors, because of the force required to mount a socket-based cooler and the narrower, 2-sided mounting mechanism (Slot 1 featured 4-point mounting). As such, and because the 0.13 µm Tualatin had an even smaller core surface area than the 0.18 µm Coppermine, Intel installed the metal heatspreader on Tualatin and all future desktop processors.

The Tualatin core was named after the Tualatin Valley and Tualatin River in Oregon, where Intel has large manufacturing and design facilities.

Pentium III's SSE implementation

Pentium III CPU mounted on a motherboard

Since Katmai was built in the same 0.25 µm process as Pentium II "Deschutes", it had to implement SSE using as little silicon as possible. To achieve this goal, Intel implemented the 128-bit architecture by double-cycling the existing 64-bit data paths and by merging the SIMD-FP multiplier unit with the x87 scalar FPU multiplier into a single unit. To utilize the existing 64-bit data paths, Katmai issues each SIMD-FP instruction as two μops. To compensate partially for implementing only half of SSE’s architectural width, Katmai implements the SIMD-FP adder as a separate unit on the second dispatch port. This organization allows one half of a SIMD multiply and one half of an independent SIMD add to be issued together bringing the peak throughput back to four floating point operations per cycle — at least for code with an even distribution of multiplies and adds.

The issue was that Katmai’s hardware-implementation contradicted the parallelism model implied by the SSE instruction-set. Programmers faced a code-scheduling dilemma: Should the SSE-code be tuned for Katmai's limited execution resources, or should it be tuned for a future processor with more resources? Katmai-specific SSE optimizations yielded the best possible performance from the Pentium III family, but was suboptimal for later Intel processors, such as the Pentium 4 and Core.

Core specifications

Katmai (0.25 µm)

• L1-Cache: 16 + 16 KiB (Data + Instructions)
• L2-Cache: 512 KiB, external chips on CPU module at 50% of CPU-speed
• MMX, SSE
• Slot 1 (SECC, SECC2)
• Front side bus: 100, 133 MHz
• VCore: 2.0 V, (600 MHz: 2.05 V)
• First release: May 17, 1999
• Clockrate: 450-600 MHz
  • 100 MHz FSB: 450, 500, 550, 600 MHz
  • 133 MHz FSB: 533, 600 MHz (B-models)

Coppermine (0.18 µm)

• L1-Cache: 16 + 16 KiB (Data + Instructions)
• L2-Cache: 256 KiB, fullspeed
• MMX, SSE
• Slot 1 (SECC2), Socket 370 (FC-PGA)
• Front side bus: 100, 133 MHz
• VCore: 1.6V, 1.65V, 1.70V, 1.76V (cD0, see below)
• First release: October 25, 1999
• Clockrate: 500 - 1133 MHz
  • 100 MHz FSB: 500, 550, 600, 650, 700, 750, 800, 850, 900, 1000, 1100 MHz (E-Models)
  • 133 MHz FSB: 533, 600, 667, 733, 800, 866, 933, 1000, 1133 MHz (EB-Models)

Coppermine-T (0.18 µm)

• L1-Cache: 16 + 16 KiB (Data + Instructions)
• L2-Cache: 256 KiB, fullspeed
• MMX, SSE
• Socket 370 (FC-PGA, FC-PGA2)
• Front side bus: 100 and 133 MHz
• VCore: 1.75 V
• First release: June 2001
• Clockrate: 600 - 1133 MHz
  • 133 MHz FSB: 800, 933, 1000, 1133 MHz

Tualatin (0.13 µm)

• L1-Cache: 16 + 16 KiB (Data + Instructions)
• L2-Cache: 256 or 512 KiB, fullspeed
• MMX, SSE, Hardware prefetch
• Socket 370 (FC-PGA2)
• Front side bus: 133 MHz
• VCore: 1.45, 1.475 V
• First release: 2001
• Clockrate: 1000 - 1400 MHz
  • Pentium III (256 KiB L2-Cache): 1000, 1133, 1200, 1333, 1400 MHz
  • Pentium III-S (512 KiB L2-Cache): 1133, 1266, 1400 MHz

Controversy about privacy issues

The Pentium III was the first CPU to include an unique, retrievable, identification number, called PSN (Processor Serial Number). A Pentium III's PSN can be read by software through the CPUID instruction if this feature has not been disabled in BIOS.

On November 29 1999, the Science and Technology Options Assessment Panel (STOA) of the European Parliament, following their report on electronic surveillance techniques asked parliamentary committee members to consider legal measures that would "prevent these chips from being installed in the computers of European citizens."

Eventually Intel decided to remove the PSN feature on Tualatin-based Pentium IIIs, and the feature was not carried through to the Pentium 4 or Pentium M.

External links

• Listing of various PII, PIII, and Celeron alphanumeric model designations
• Intel Pentium III technical specifications Nice overview, but use with caution: Some information on this site is in conflict with Intel's documentation.
• Comparison of 7th generation x86 CPU architectures
• Intel FAQ about the pentium III processor serial number