Pentium
|
Pentium logo, with MMX enhancement |
The
Pentium is a fifth-generation
x86 architecture
microprocessor from
Intel, developed by
Vinod Dham. It was the successor to the
486 line, and was first shipped on
March 22,
1993.
The Pentium was originally to be named 80586 or i586, to follow the naming convention of previous generations. However, Intel was unable to convince a court to allow them to
trademark a number (such as 486), in order to prevent competitors such as
Advanced Micro Devices from branding their processors with similar names (such as AMD's Am486). Intel enlisted the help of
Lexicon Branding to create a brand that could be trademarked. The
Pentium brand was very successful, and was maintained through several generations of processors, from the
Pentium Pro to the
Pentium Extreme Edition. Intel has retired the brand and replaced it with the "Intel Core" brand. The first
Intel Core, released in January
2006, extended the
Pentium M microarchitecture. The
Intel Core 2, released in July 2006, features the new
Intel Core Microarchitecture.
In
programming, it is sometimes necessary to distinguish the original Pentium processor architecture from later Pentium-branded architectures. For these cases,
i586 is often used to refer to all the early Pentium processors, as well as processors made by Intel's competitors that can run
machine code targeted to the early Pentiums.
|
Pentium Overdrive for 486 systems |
*
Superscalar architecture - The Pentium has two datapaths (pipelines) that allow it to complete more than one instruction per clock cycle. One pipe (called "U") can handle any instruction, while the other (called "V") can handle the simplest, most common instructions. The use of more than one pipeline is a characteristic typical of
RISC processors designs, the first of many to be implemented on the x86 platform, thus signaling the road to take, and showing that it was possible to merge both technologies, creating almost “hybrid” processors.
*
64-bit data path - This doubles the amount of information pulled from the memory on each fetch. This doesn't mean that the Pentium can execute so-called
64-bit applications; its main registers are still 32 bits wide.
*
MMX instructions (later models only) - A basic
SIMD instruction set extension designed for use in
multimedia applications.
Pentium architecture chips offered just under twice the performance of a 486 processor per clock cycle. The fastest Intel 486 parts were almost the same speed as a first-generation Pentium, and a few late-model
AMD 486 parts were roughly equal to the Pentium 75.
The earliest Pentiums were released at the clock speeds of 66 MHz and 60 MHz. Later on 75, 90, 100, 120, 133, 150, 166, 200, and 233 MHz versions gradually became available. 266 and 300 MHz versions were later released for mobile computing.
Pentium OverDrive processors were released at speeds of 63 and 83 MHz as an upgrade option for older 486-class computers.
| Code name | P5 | P54 | P54C | P55C | P55C (Tillamook) | | Process size (µm) | 0.80 | 0.60 | 0.35 | 0.25 |
|---|
| Clock speed (MHz) | 60 | 66 | 75 | 90 | 100 | 120 | 133 | 150 | 166 | 200 | 120* | 133* | 150* | 166 | 200 | 233 | 200 | 233 | 266 | 300 |
|---|
| Voltage | 5.0 | 5.0 | 3.3 | 3.3 | 3.3 | 3.3 | 3.3 | 3.3 | 3.3 | 3.3 | 2.8 | 2.8 | 2.8 | 2.8 | 2.8 | 2.8 | 1.8 | 1.8 | 1.8 | 1.8 |
|---|
| Introduced | March 1993 | Oct. 1994 | March 1994 | March 1995 | June 1995 | Jan. 1996 | June 1996 | colspan="2" | Oct. 1996 | June 1997 | Sept. 1997 | Jan. 1998 | Jan. 1999 |
|---|
*
* These were only available for notebooks.P5, P54, P54C
The original Pentium microprocessor had the internal code name P5, and was a pipelined in-order superscalar microprocessor, produced using a 0.8
µm process. It was followed by the P54, a shrink of the P5 to a 0.6 µm process, which was dual-processor ready and had an internal clock speed different from the front side bus (it's much more difficult to increase the bus speed than to increase the internal clock). In turn, the P54 was followed by the P54C, which used a 0.35 µm process - a pure
CMOS process, as opposed to the Bipolar CMOS process that was used for the earlier Pentiums.
The early versions of 60-100 MHz Pentiums had a problem in the floating point unit that, in rare cases, resulted in reduced precision of division operations. This bug, discovered in Lynchburg, Virginia in 1994, became known as the
Pentium FDIV bug and caused great embarrassment for Intel, which created an exchange program to replace the faulty processors with corrected ones. The 60 and 66 Mhz 0.8
µm versions of the Pentium processors were also known for their fragility and their (for the time) high levels of heat production - in fact, the Pentium 60 and 66 were often nicknamed "coffee warmers". They were also known as "high voltage Pentiums", due to their 5V operation. The heat problems were removed with the P54, which ran at a much lower voltage (3.3V). P5 Pentiums used
Socket 4, while P54 started out on
Socket 5 before moving to
Socket 7 in later revisions. All desktop Pentiums from P54C onwards used Socket 7. Another bug known as
f00f bug was discovered soon, fortunately operating system vendors responded by implementing workarounds that prevented the crash.
The
Pentium OverDrive for
486 systems, a sort of oddity among the other Pentium processors, was released in early 1995. The Pentium architecture had to be modified in many ways to operate on the 486 platform's narrower 32-bit data bus and slower cache architecture. As such, the chip came equipped with a 32 KB L1 cache, double the what a pre-P55C Pentium came equipped with. The chip also included an attached fan/heatsink assembly in addition to onboard power regulation to convert the frequent 5 volt power circuitry on 486 boards down to the Pentium's 3.3 volt needs.
P55C, Tillamook
Subsequently, the P55C was released as the
Pentium with MMX Technology (usually just called
Pentium MMX); it was based on the P5 core, the 0.35 µm process was also used for this series, but it had a new set of 57 "MMX" instructions intended to improve performance on multimedia tasks, such as encoding and decoding digital media data.
The new instructions work on new data types: 64-bit packed vectors of either eight 8-bit integers, four 16-bit integers, two 32-bit integers, or 1 64-bit integer. So, for example, the PADDUSB (Packed ADD Unsigned Saturated Byte) instruction adds two vectors, each containing eight 8-bit unsigned integers together, pairwise; each addition that would
overflow saturates, yielding 255, the maximum unsigned value that can be represented in a byte. These rather specialized instructions generally require special coding by the programmer for them to be used. MMX did not achieve significant popularity until after the P55C's lifetime.
The performance of the P55C was improved over previous versions by a doubling of the Level 1
CPU cache from 16 KiB to 32 KiB.
Pentium P55C notebook CPUs used a "mobile module" that held the CPU. This module was a
PCB with the CPU directly attached to it in a special smaller form factor. The module snapped to the notebook motherboard and typically a heat spreader plate was installed and made contact with the module. Such notebooks frequently used the Intel
430MX chipset, a feature-reduced
430FX. However, with Tillamook (named after a
city in Oregon), the module also held the
430TX chipset along with the system's 512 KiB
SRAM cache memory.
|
Pentium III chip mounted on a motherboard |
Intel has retained the Pentium trademark for naming later generations of processor architectures, which are internally quite different from the Pentium itself:
*
Pentium Pro*
Pentium II*
Pentium III*
Pentium 4*
Pentium M*
Pentium D*
Pentium Extreme EditionIt can be seen from this that brand name is only loosely related to the nature of a CPU's microarchitecture. The Pentium brand is traditionally used for desktop and notebook parts, the
Celeron brand is used for "value" parts (typically lower performance and lower price), and the
Xeon brand is used for high-performance parts suitable for
servers and
workstations. The same basic microarchitecture may be used for all brands, but implementations may differ in clock speeds,
cache sizes, and package and sockets. Moreover, the same name is used for chips with unrelated microarchitectures.
The
Intel Core processor uses the same microarchitecture as the Pentium M processors, but discards the Pentium M name (and also uses Intel's new logo); with the release of the
Intel Core 2 processors on July 27, 2006, Intel has retired the Pentium name.
*
Pentium Compatible Processor*
CPU design*
IA-32 processor design and instruction set
