![Cyrix-Advert](https://upload.wikimedia.org/wikipedia/commons/4/48/Cyrix-Advert.jpg)
The Cyrix 5x86 was a line of
x86
x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was intr ...
microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...
s designed by
Cyrix and released on June 5 of 1995. Cyrix, being a fabless company, had the chips manufactured by
IBM. The line came out about 5 months before the more famous
Cyrix 6x86
The Cyrix 6x86 is a line of sixth-generation, 32-bit x86 microprocessors designed and released by Cyrix in 1995. Cyrix, being a fabless company, had the chips manufactured by IBM and SGS-Thomson. The 6x86 was made as a direct competitor to In ...
. The
Cyrix 5x86 was one of the fastest
CPUs ever produced for
Socket 3
Socket 3 was a series of CPU sockets for various x86 microprocessors. It was sometimes found alongside a secondary socket designed for a math coprocessor chip, such as the 487. Socket 3 resulted from Intel's creation of lower voltage microproce ...
computer
A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
systems. With better performance in most applications than an
Intel
Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...
Pentium
Pentium is a brand used for a series of x86 architecture-compatible microprocessors produced by Intel. The original Pentium processor from which the brand took its name was first released on March 22, 1993. After that, the Pentium II and P ...
processor at 75
MHz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...
, the Cyrix Cx5x86 filled a gap by providing a medium-performance processor option for
486 Socket 3
motherboards (which are incapable of handling Intel's
Pentium
Pentium is a brand used for a series of x86 architecture-compatible microprocessors produced by Intel. The original Pentium processor from which the brand took its name was first released on March 22, 1993. After that, the Pentium II and P ...
CPUs, apart from the
Pentium Overdrive The Pentium OverDrive was a microprocessor marketing brand name used by Intel, to cover a variety of consumer upgrade products sold in the mid-1990s. It was originally released for 486 motherboards, and later some Pentium sockets. Intel dropped the ...
).
The IBM 5x86C is an
IBM branded and produced version of the
Cyrix-designed Cyrix Cx5x86
CPU. Previous IBM x86 processors,
IBM 386SLC The 386SLC was an Intel-licensed version of the 386SX (32-bit internal, 16-bit external, 24-bit memory addressing), developed and manufactured by IBM in 1991. It included power-management capabilities and an 8KB internal CPU cache, which enabled i ...
and
IBM 486SLC The 386SLC was an Intel-licensed version of the 386SX (32-bit internal, 16-bit external, 24-bit memory addressing), developed and manufactured by IBM in 1991. It included power-management capabilities and an 8KB internal CPU cache, which enabled i ...
, were based on modified Intel designs.
Design
The Cyrix 5x86 processor, codename "M1sc", was based on a scaled-down version of the "M1" core used in the Cyrix
6x86
The Cyrix 6x86 is a line of sixth-generation, 32-bit x86 microprocessors designed and released by Cyrix in 1995. Cyrix, being a fabless company, had the chips manufactured by IBM and SGS-Thomson. The 6x86 was made as a direct competitor to Int ...
, which provided 80% of the performance for a 50% decrease in
transistor
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...
s over the 6x86 design. It had the
32-bit
In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculation ...
memory bus of an ordinary 486 processor, but internally had much more in common with
fifth-generation processors such as the Cyrix 6x86, the
AMD K5
The K5 is AMD's first x86 processor to be developed entirely in-house. Introduced in March 1996, its primary competition was Intel's Pentium microprocessor. The K5 was an ambitious design, closer to a Pentium Pro than a Pentium regarding techn ...
, and the Intel Pentium, and even the sixth-generation Intel
Pentium Pro
The Pentium Pro is a sixth-generation x86 microprocessor developed and manufactured by Intel and introduced on November 1, 1995. It introduced the P6 microarchitecture (sometimes termed i686) and was originally intended to replace the original ...
. The chip featured near-complete support for i486 instructions, but very limited support for Pentium instructions. Some performance-enhancing features of the CPU were intentionally disabled due to potentially stability-threatening
bugs which were not fixed before release time (these features can be enabled with freely downloadable software utilities; see below).
The similarly named
SGS-Thomson
STMicroelectronics N.V. commonly referred as ST or STMicro is a Dutch multinational corporation and technology company of French-Italian origin headquartered in Plan-les-Ouates near Geneva, Switzerland and listed on the French stock market. ST ...
(STMicroelectronics) ST5x86 and
IBM 5x86C were licensed rebrandings of the Cyrix design (IBM and ST physically produced Cyrix's CPUs for them), marketed separately but identical for practical purposes, apart from the availability of a 75 MHz edition which Cyrix did not bring to market, and slight differences in voltage requirements. The Cyrix 5x86 design, however, should not be confused with the similarly named
AMD Am5x86 which was essentially a clock-quadrupled 486 (not an all-new design like the Cyrix part) but which had broadly similar performance, used the same Socket 3, and was introduced at the end of the same year.
Cyrix's 5x86 was a very short-lived chip, having a market life of only six months. It is likely Cyrix could have continued to successfully sell processors based on Socket 3, but canned the 5x86 so that it would not compete with its then new 6x86 offerings.
Controversies and anomalies
The official Cyrix 5x86 website boasted about several features of the chip that were disabled by default in the final versions. The most controversial of these features was the "branch-prediction" feature, which was enabled in the benchmarks results on the company website when comparing the chip to Intel's Pentium processor. While it was possible to enable the extra features using a special software utility, it usually resulted in an unstable system, especially on earlier steppings of the chip when running 32-bit code.
There are also many rumours surrounding a 133 MHz, clock-quadrupled version of the Cyrix 5x86. The 133 MHz version is very rare, however, and producers of upgrade kits were given preferential access to it, notably Gainbery. Some of the 100 and 120 MHz parts also contain support for the 4X multiplier setting, and some of these chips may also work at 133 MHz. However, the 5x86 is not known to overclock well; 120 MHz is generally considered to be pushing the limitations of the process on which it was fabricated. An 80 MHz (2×40 MHz) 5x86 also exists, but is unclear as to whether or not it was ever officially released.
IBM's 5x86C was considered to be more conservatively rated than the Cyrix branded parts, and operated at a lower voltage (3.3V). For example: what Cyrix would rate as a 100 MHz part, IBM would mark as 75 MHz. IBM 5x86C was available as 75 MHz and 100 MHz parts. A few examples of 120 MHz parts also exist, but they have early production dates indicating that they may have been produced prior to IBM's decision to scale back clock speeds. 5x86C also had a much longer production run than the Cyrix branded parts. IBM continued to produce 5x86C at least until late 1998 (
QFP
A quad flat package (QFP) is a surface-mounted integrated circuit package with "gull wing" leads extending from each of the four sides. Socketing such packages is rare and through-hole mounting is not possible. Versions ranging from 32 to 304 ...
only), whereas Cyrix's own part was discontinued in 1996. Parts which implement the 4X multiplier or Stepping 1 Rev 3 cores are not known to exist.
Specifications
![Cyrix 5x86 die](https://upload.wikimedia.org/wikipedia/commons/a/ab/Cyrix_5x86_die.jpg)
* iDX4WB pinout, 168 pins
*
Socket 3
Socket 3 was a series of CPU sockets for various x86 microprocessors. It was sometimes found alongside a secondary socket designed for a math coprocessor chip, such as the 487. Socket 3 resulted from Intel's creation of lower voltage microproce ...
* 2.0 million transistors on 0.65 micrometre process
* 144mm² die
* 3.45 volts
* 16
kilobyte
The kilobyte is a multiple of the unit byte for digital information.
The International System of Units (SI) defines the prefix '' kilo'' as 1000 (103); per this definition, one kilobyte is 1000 bytes.International Standard IEC 80000-13 Quant ...
s unified level-one cache
100 MHzcapable edition for 33 MHz (33×3), and 50 MHz (50×2)
front side bus
A front-side bus (FSB) is a computer communication interface ( bus) that was often used in Intel-chip-based computers during the 1990s and 2000s. The EV6 bus served the same function for competing AMD CPUs. Both typically carry data between the ...
100 MHzcapable edition for 33 MHz (33×3), and 25 MHz (25×4)
front side bus
A front-side bus (FSB) is a computer communication interface ( bus) that was often used in Intel-chip-based computers during the 1990s and 2000s. The EV6 bus served the same function for competing AMD CPUs. Both typically carry data between the ...
120/133 MHzcapable edition for 40 MHz (40×3) and 33 MHz (33×4)
front side bus
A front-side bus (FSB) is a computer communication interface ( bus) that was often used in Intel-chip-based computers during the 1990s and 2000s. The EV6 bus served the same function for competing AMD CPUs. Both typically carry data between the ...
.
References
External links
{{commons category
Comparative performance benchmarks*
ttps://web.archive.org/web/20031020013939/http://homepage3.nifty.com/sandy55/PowerBoard/PowerBoard.html Information on write-back cache performance-enhancing utility from Evergreen Techsee "Cyrix5x86" section in the middle of the page and "et9603.exe" hyperlink)
Cx586
586
__NOTOC__
Year 586 ( DLXXXVI) was a common year starting on Tuesday (link will display the full calendar) of the Julian calendar. The denomination 586 for this year has been used since the early medieval period, when the Anno Domini calendar ...