Cyrix Corporation
Industry Semiconductors
Fate Merged
Successor National Semiconductor, later VIA Technologies
Founded 1988
Defunct November 11, 1997
Headquarters Richardson, TX, USA
Key people Jerry Rogers, Tom Brightman (founders)[1]
Products 6x86
Employees approx. 300

Cyrix Corporation was a microprocessor developer that was founded in 1988 in Richardson, Texas as a specialist supplier of high-performance math coprocessors for 286 and 386 microprocessors. The company was founded by former Texas Instruments (TI) staff members and had a long but troubled relationship with TI throughout its history. Cyrix founder Jerry Rogers aggressively recruited engineers and pushed them, eventually assembling a small but efficient design team of 30 people.

Cyrix merged with National Semiconductor on 11 November 1997.



The first Cyrix product for the personal computer market was a x87 compatible FPU coprocessor. The Cyrix FasMath 83D87 and 83S87 were introduced in 1989. The FasMath was the fastest 386-compatible coprocessor and provided up to 50% more performance than the Intel 80387. Cyrix FasMath 82S87, a 80287-compatible chip was developed from the Cyrix 83D87 and has been available since 1991.

Cyrix FasMath

Its early CPU products included the 486SLC and 486DLC, released in 1992, which, despite their names, were pin-compatible with the 386SX and DX, respectively. While they added an on-chip L1 cache and the 486 instruction set, performance-wise they were somewhere between the 386 and the 486. The chips were mostly used as upgrades by end users looking to improve performance of an aging 386 and especially by dealers, who by changing the CPU could turn slow-selling 386 boards into budget 486 boards. The chips were widely criticized in product reviews for not offering the performance suggested by their names, and for the confusion caused by their naming similarity with Intel's SL line and IBM's SLC line of CPUs, neither of which was related to Cyrix's SLC. The chips did see use in very low-cost PC clones and in laptops.

Cyrix would later release the Cyrix 486SRX2 and 486DRX2, which were essentially clock-doubled versions of the SLC and DLC, marketed exclusively to consumers as 386-to-486 upgrades.

Eventually Cyrix was able to release a 486 that was pin-compatible with its Intel counterparts. However, the chips were later to market than AMD's 486s and benchmarked slightly slower than AMD and Intel counterparts, which relegated them to the budget and upgrade market. While AMD had been able to sell some of its 486s to large OEMs, notably Acer and Compaq, Cyrix had not. The Cyrix chips did gain some following with upgraders, as their 50-, 66- and 80 MHz 486 CPUs ran at 5 volts, rather than the 3.3 volts used by AMD, making the Cyrix chips usable as upgrades in early 486 motherboards.

In 1995, with its Pentium clone not yet ready to ship, Cyrix repeated its own history and released the Cx5x86, which plugged into a 486 socket, ran at 100, 120 or 133 MHz, and yielded performance comparable to that of a Pentium running at 75 MHz. While AMD's Am5x86 was little more than a clock-quadrupled 486 with a new name, Cyrix's 5x86 implemented some Pentium-like features.

Cyrix MediaGX

Later in 1995 Cyrix released its best-known chip, the 6x86 (M1). This processor continued the Cyrix tradition of making faster replacements for Intel designed sockets. However, the 6x86 was the star performer in the range, giving a tangible performance boost over the Intel "equivalent". 6x86 processors were given names such as P166+ indicating a performance better than a Pentium 166MHz processor. In fact, the 6x86 processor was clocked at a significantly lower speed than the Pentium part it outperformed. Initially Cyrix tried to charge a premium for its extra performance, but the 6x86's math coprocessor was not as fast as that in the Intel Pentium. The main difference was not one of actual computing performance on the coprocessor, but a lack of instruction pipelining. Due to the increasing popularity of first-person 3D games, Cyrix was forced to lower its prices. While the 6x86 quickly gained a following among computer enthusiasts and independent computer shops, unlike AMD, its chips had yet to be used by a major OEM customer. The game in question causing most problems for performance was id Software's Quake. Unlike previous 3D games Quake used the pipelined Pentium FPU to do perspective correction calculations in the background while texture mapping, effectively doing two tasks at once. This wouldn't have been a big problem for the 6x86 if Quake have had a fallback to do perspective correction without the FPU like in e.g. the game Descent however id Software choose not to include this. This boosted the popularity of Intel CPUs amongst the gaming community.

The later 6x86L was a revised 6x86 that consumed less power, and the 6x86MX (M2) added MMX instructions and a larger L1 cache. The MII, based on the 6x86MX design, was little more than a name change intended to help the chip compete better with the Pentium II.

In 1996 Cyrix released the MediaGX CPU, which integrated all of the major discrete components of a PC, including sound and video, onto one chip. Initially based on the old 5x86 technology and running at 120 or 133 MHz, its performance was widely criticized but its low price made it successful. The MediaGX led to Cyrix's first big win, when Compaq used it in its lowest-priced Presario 2100 and 2200 computer. This led to further MediaGX sales to Packard Bell and also seemed to give Cyrix legitimacy, as 6x86 sales to Packard Bell and eMachines quickly followed.

Later versions of the MediaGX ran at speeds of up to 333 MHz and added MMX support. A second chip was added to extend its video capabilities.

PR system

Because the 6x86 was more efficient on an instructions-per-cycle basis than Intel's Pentium, and because Cyrix sometimes used a faster bus speed than either Intel or AMD, Cyrix and competitor AMD co-developed the controversial PR system in an effort to compare its products more favorably with Intel's. Since a 6x86 running at 133 MHz generally benchmarked slightly faster than a Pentium running at 166 MHz, the 133 MHz 6x86 was marketed as the 6x86-P166+. Legal action from Intel, who objected to the use of the strings "P166" and "P200" in non-Pentium products, led to Cyrix adding the letter "R" to its names.

The PR nomenclature was controversial because while Cyrix's chips generally outperformed Intel's when running productivity applications, on a clock-for-clock basis its chips were slower for floating point operations, so the PR system broke down when running the newest games. Additionally, since the 6x86's price encouraged its use in budget systems, performance could drop even further when compared with Pentium systems that were using faster hard drives, video cards, sound cards, and modems.

Although AMD used the PR rating in its early K5 chips, it soon abandoned the PR rating, although it would later use a similar concept in marketing its later CPUs.

Manufacturing partners

6x86MX under the IBM name

Cyrix had always been a fabless company: Cyrix designed and sold their own chips, but contracted the actual semiconductor manufacturing to an outside foundry. In the early days, Cyrix mostly used Texas Instruments production facilities and SGS Thomson (now STMicroelectronics). In 1994, following a series of disagreements with Texas Instruments, and production difficulties at SGS Thomson, Cyrix turned to IBM Microelectronics, whose production technology rivaled that of Intel.

As part of the manufacturing agreement between the two companies, IBM received the right to build and sell Cyrix-designed CPUs under the IBM name. While some in the industry speculated this would lead to IBM using 6x86 CPUs extensively in its product line and improve Cyrix's reputation, IBM continued to mostly use Intel CPUs, and to a lesser extent, AMD CPUs, in the majority of its products and only used the Cyrix designs in a few budget models, mostly sold outside of the United States. IBM instead sold its 6x86 chips on the open market, competing directly against Cyrix and sometimes undercutting Cyrix's prices.

Legal troubles

Unlike AMD, Cyrix had never manufactured or sold Intel designs under a negotiated license. Cyrix's designs were the result of meticulous in-house reverse engineering. Thus, while AMD's 386s and even 486s had some Intel-written microcode software, Cyrix's designs were completely independent. Focused on removing potential competitors, Intel spent many years in legal battles with Cyrix, consuming Cyrix financial resources, claiming that the Cyrix 486 violated Intel's patents, when in reality the design was proven independent.

Intel largely lost the Cyrix case. But the final settlement was out of court: Intel agreed that Cyrix had the right to produce their own x86 designs in any foundry that happened to already hold an Intel license. Both firms gained out of this: Cyrix could carry on having their CPUs made by Texas Instruments, SGS Thomson, or IBM, all holders of Intel cross-licenses; Intel avoided a potentially embarrassing loss.

The follow-on 1997 Cyrix-Intel litigation was the reverse: instead of Intel claiming that Cyrix 486 chips violated their patents, now Cyrix claimed that Intel's Pentium Pro and Pentium II violated Cyrix patents—in particular, power management and register renaming techniques. The case was expected to drag on for years but was settled quite promptly, by another mutual cross-license agreement. Intel and Cyrix now had full and free access to each other's patents. The settlement didn't say whether the Pentium Pro violated Cyrix patents or not; it simply allowed Intel to carry on making them either way—exactly as the previous settlement sidestepped Intel's claim that the Cyrix 486 violated Intel patents.

Merger with National Semiconductor

In August 1997, while the litigation was still in progress, Cyrix merged with National Semiconductor (who also already held an Intel cross-license). This provided Cyrix with an extra marketing arm and access to National Semiconductor fabrication plants, which were originally constructed to produce RAM and high-speed telecommunications equipment. Since the manufacture of RAM and CPUs is similar, industry analysts at the time believed the marriage made sense. The IBM manufacturing agreement remained for a while longer, but Cyrix eventually switched all their production over to National's plant. The merger improved Cyrix's financial base and gave them much better access to development facilities.

The merger also resulted in a change of emphasis: National Semiconductor's priority was single-chip budget devices like the MediaGX, rather than higher performance chips like the 6x86 and MII. Whether National Semiconductor doubted Cyrix's ability to produce high-performance chips or feared competing with Intel at the high end of the market is open to debate. The MediaGX, with no direct competition in the marketplace and with continual pressure on OEMs to release lower-cost PCs, looked like the safer bet.

National Semiconductor ran into financial trouble soon after the Cyrix merger, and these problems hurt Cyrix as well. By 1999, AMD and Intel were leapfrogging one another in clock speeds, reaching 450 MHz and beyond while Cyrix took almost a year to push the MII from PR-300 to PR-333. Neither chip actually ran at 300 MHz. A problem suffered by many of the MII models was that they used a non-standard 83 MHz bus. The vast majority of Socket 7 motherboards used a fixed 1/2 divider to clock the PCI bus, normally at 30 MHz or 33 MHz. With the MII's 83 MHz bus, this resulted in the PCI bus running alarmingly out of spec at 41.5 MHz. At this speed, many PCI devices could become unstable or fail to operate. Some motherboards supported a 1/3 divider, which resulted in the PCI bus running at 27.7 MHz. This was more stable, but adversely affected system performance. The problem was only fixed in the final few models, which supported a 100 MHz bus. Almost all of the 6x86 line produced a large amount of heat, and required quite large heatsink/fan combos (for the time) to run properly. There was also a problem which made the 6x86 incompatible with the then-popular Sound Blaster AWE64 sound card. Only 32 of its potential 64 voice polyphony could be utilized, as the WaveSynth/WG software synthesizer relied on a Pentium-specific instruction which the 6x86 lacked. Meanwhile, the MediaGX faced pressure from Intel's and AMD's budget chips, which also continued to get less expensive while offering much greater performance. Cyrix, whose product had been considered a performance product in 1996, had fallen to the mid-range, then the entry level, and to the fringe of the entry level and was in danger of completely losing its market.

Cyrix MII 433GP front
Cyrix MII 433GP back

The last Cyrix-badged microprocessor was the Cyrix MII-433GP which ran at 300 MHz (100x3) and performed faster than an AMD K6/2-300 on FPU calculations (as benched with Dr. Hardware). However, this chip was regularly pitted against actual 433 MHz processors from other manufacturers. Arguably this made the comparison unfair, even though it was directly invited by Cyrix's own marketing.

National Semiconductor distanced itself from the CPU market, and without direction, the Cyrix engineers left one by one. By the time National Semiconductor sold Cyrix to VIA Technologies, the design team was no more and the market for the MII had disappeared. VIA used the Cyrix name on a chip designed by Centaur Technology, since VIA believed Cyrix had better name recognition than Centaur, or possibly even VIA.

Cyrix's failure is described by Glenn Henry CEO of Centaur Technology as "Cyrix had a good product, but they got bought by a 'big smokestack' company and they got bloated. When Via bought Cyrix, they had 400, and we had 60, and we were turning out more product."[2]

National Semiconductor retained the MediaGX design for a few more years, renaming it the Geode and hoping to sell it as an integrated processor. They sold the Geode to AMD in 2003.

In June 2006, AMD unveiled the world's lowest-power x86-compatible processor that consumes only 0.9 watts of power. This processor is based on the Geode core, demonstrating that Cyrix's architectural ingenuity still survives.


Although the company was short-lived and the brand name is no longer actively used by its current owner, Cyrix's competition with Intel created the market for budget CPUs, which cut the average selling price of PCs and ultimately forced Intel to release its Celeron line of budget processors and cut the prices of its faster processors more quickly in order to compete.

Additionally, the acquisition of Cyrix's intellectual property and agreements would be used by VIA to defend itself from its own legal troubles with Intel, even after VIA Technologies stopped using the Cyrix name.

In popular media

The film Eraser featured a defense corporation known as "Cyrex". Cyrix became concerned about the potential name conflict, and contacted the film production company. The name was then retroactively digitally edited to become "Cyrez" to avoid any confusion.


  • This is an edited version of a document that first appeared at, and is used with permission. Some of the less suitable material has been omitted.

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