View source for Cyrix Cx486SLC

{{Short description|Cyrix x86 microprocessor}}
{{redirect|486SLC|the unrelated IBM CPU of the same name|IBM 386SLC#IBM 486SLC}}
{{Infobox CPU
|name           = Cyrix Cx486SLC
|image          = Cyrix Cx486SLCe-V25MP DF7339E top.jpg
|image_size     = 200px
|caption        = Cyrix Cx486SLC Microprocessor
|soldby         = [[Cyrix]], [[Texas Instruments]]
|designfirm     = Cyrix
|manuf1         = {{plainlist|
*Texas Instruments
*SGS-Thomson
}}
|produced-start = May 1992
|produced-end   =
|model          =
|transistors    =
|slowest        = 20 |slow-unit = MHz
|fastest        = 50 |fast-unit = MHz
|fsb-slowest    = 20 |fsb-slow-unit = MHz
|fsb-fastest    = 40 |fsb-fast-unit = MHz
|data-width     = 16
|address-width  = 24
|sock1          =
|sock2          =
|brand1         =
|arch           = [[x86-16]], [[IA-32]]
|microarch      =
|cpuid          =
|code           =
|numcores       = 1
|co-processor   = 287, 387SX
|l1cache        = {{plainlist|
*1 KB (Cx486)
*8 KB (TI486SXLC)
}}
|application    = Desktop
|successor      = [[Cyrix Cx486]]
|announced=}}

The '''Cyrix Cx486SLC''' is a x86 microprocessor that was developed by [[Cyrix]]. It was one of Cyrix's first [[Central processing unit|CPU]] offerings, released after years of selling [[Floating-point unit|math coprocessors]] that competed with [[Intel|Intel's]] units and offered better performance at a comparable or lower price. It was announced in March of 1992,<ref>{{Cite news|date=30 March 1992|title=It's a 386 - no, it's a 486!|volume=26, No. 13.|pages=8|work=[[Computerworld]]|publisher=[[IDG Enterprise]]|url=https://books.google.com/books?id=ioRslYZXVkAC&dq=Cyrix+Cx486SLC&pg=PA8|access-date=22 February 2022|issn=0010-4841}}</ref> and released 2 months later in May, with a price of $119.<ref>{{Cite news|date=31 March 1992|title=Cyrix-Intel market fight heats up with new chip|work=[[The Desert Sun]]|url=https://www.newspapers.com/image/748935605/?terms=Cyrix%20Cx486SLC&match=1|access-date=20 February 2022}}</ref> It was priced competitively against the [[Intel]] 486SX, causing Intel to lower the price of their chip from $286 to $119 in just days.<ref>{{Cite news|date=16 April 1993|title=Competition benefits consumers, Advancing technology produces good buys on computer chips|work=[[Argus-Leader]]|url=https://www.newspapers.com/image/239878557/?terms=Cyrix%20Cx486DLC&match=1|access-date=21 February 2022}}</ref>

== Specifications ==
The 486SLC is based on the [[i386SX]] bus, and was intended as an entry-level chip to compete with the Intel 386SX and 486SX. [[STMicroelectronics|SGS-Thomson]] and [[Texas Instruments]] manufactured the 486SLC for Cyrix.<ref>{{Cite news |date=31 March 1992 |title=TEXAS "TO MAKE CYRIX Cx486" AS WELL AS SGS THOMSON |work=Tech Monitor |url=https://techmonitor.ai/technology/texas_to_make_cyrix_cx486_as_well_as_sgs_thomson |access-date=2 March 2022}}</ref><ref>{{Cite news |last=Quinlan |first=Tom |date=18 May 1992 |title=TI licenses Cyrix 486SLC Technology |volume=14 |pages=6 |work=[[InfoWorld]] |issue=20 |publisher=[[InfoWorld Media Group, Inc.]] |url=https://books.google.com/books?id=XlEEAAAAMBAJ&dq=sgs-thomson+486slc&pg=PA6 |access-date=3 March 2022 |issn=0199-6649}}</ref> Texas Instruments also sold it under its own name as TX486SLC. Later, Texas Instruments also released their own version of the chip, the TI486SXLC which featured 8KB internal cache vs 1KB in the original Cyrix design.<ref>{{Cite book|url=http://www.bitsavers.org/components/ti/TI486/1994_TI486SXLC_and_TI486SXL_Microprocessors_Reference_Guide.pdf|title=TI486SXLC and TI486SXL Microprocessors Reference Guide|publisher=[[Texas Instruments]]|year=1994|pages=1.2|chapter=Features}}</ref> These chips went under the name Potomac, and Cyrix would receive full royalties for them.<ref>{{Cite news|date=8 October 1993|title=COMPANY NEWS; TEXAS INSTRUMENTS INTRODUCES LINE OF 486 CHIPS|work=[[The New York Times]]|url=https://www.nytimes.com/1993/10/08/business/company-news-texas-instruments-introduces-line-of-486-chips.html|access-date=8 February 2022}}</ref> The similarly named [[IBM 486SLC]], 486SLC2, 486SLC3 (16-bit external bus version of IBM 486DLC aka Blue Lightning) and [[386SLC|IBM 386SLC]] are often confused with the Cyrix chips, but are not related and instead based on an Intel CPU core.

Introduced in May 1992, like the later and more famous [[Cyrix Cx5x86]] it was a hybrid CPU, incorporating features of a new CPU (in this case the [[Intel 80486]]) while having a pin out similar to the existing 386SX, enabling existing board designs to be easily modified for the new chip.<ref name=":0">{{Cite news|last=Quinlan|first=Tom|date=6 April 1992|title=Cyrix gains customers for its 486 chip|volume=14, No. 14.|page=29|work=[[InfoWorld]]|publisher=[[InfoWorld Media Group, Inc.]]|url=https://books.google.com/books?id=6z0EAAAAMBAJ&dq=Cyrix+Cx486SLC&pg=PA29|access-date=2 February 2022}}</ref> It ran at speeds of 20, 25, 33, and 40&nbsp;MHz, although it had difficulty running reliably at 40&nbsp;MHz using some operating systems. In December 1992 Cyrix also released the Cyrix Cx486SLC/e (25, 33&nbsp;MHz) which offered power management, and a low voltage laptop version, the 3.3v Cyrix Cx486SLC/e-V (20, 25&nbsp;MHz). In December 1993 Cyrix released a clock doubled version (25/50&nbsp;MHz) cx486SLC2,<ref>{{Cite news|last=Polilli|first=Steve|date=15 November 1993|title=Cyrix readies clock-doubled processor|volume=15, No. 46.|page=38|work=[[InfoWorld]]|publisher=[[InfoWorld Media Group, Inc.]]|url=https://books.google.com/books?id=DDsEAAAAMBAJ&dq=Cyrix+Cx486SLC2&pg=PA38|access-date=2 February 2022|issn=0199-6649}}</ref> as well as a clip-on upgrade for 386SX systems, the cx486SRx2 (16/33, 20/40 & 25/50&nbsp;MHz).<ref>{{Cite news|date=25 April 1994|title=Is the Cyrix 386-to-486 Upgrade Chip really that good? Just ask anybody.|page=79|work=[[InfoWorld]]|publisher=[[InfoWorld Media Group, Inc.]]|url=https://books.google.com/books?id=IzsEAAAAMBAJ&dq=cx486SRx2&pg=PA79|access-date=3 February 2022|issn=0199-6649}}</ref>

The 486SLC can be described as a 386SX with the 486 instruction set and 1K of onboard [[L1 cache]] added. Unfortunately it inherited the 386SX's 24-bit address bus (16&nbsp;MB max. DRAM), and 16-bit datapath which limited its memory bandwidth. Like the 386 and 486SX, it had no on-board [[X87|x87 math coprocessor]], but unlike the 486SX, it could make use of an Intel i287, 387SX or compatible [[x87]] coprocessor. Due to the limitations of the 386SX's bus and its smaller L1 cache, its performance could not compete with the 486SX when the latter was running on a full 32-bit bus.<ref>{{Cite news|last=Barr|first=Christopher|date=July 1992|title=Is the 486SLC a 386 or 486?|volume=11, No. 13.|page=40|work=[[PC Mag]]|publisher=[[Ziff Davis, Inc.]]|url=https://books.google.com/books?id=X4152M1DLygC&dq=cyrix+486SLC&pg=PA40|access-date=3 February 2022|issn=0888-8507}}</ref>

The 486SLC was primarily used in very inexpensive low-end [[motherboard]]s and PC clones. Because of its low power consumption, it also saw use in [[laptop]]s.<ref>{{Cite news|date=16 June 1992|title=Fast Inroads for Cyrix 486 Hybrid Chip|volume=11|pages=29, 32|work=[[PC Mag]]|issue=11|publisher=[[Ziff Davis, Inc.]]|url=https://books.google.com/books?id=WFhT5khImwMC&dq=Cyrix+Cx486SLC+lawsuit&pg=PT33|access-date=15 February 2022|issn=0888-8507}}</ref> The 486SLC was also available as a 32-bit version based on the i386DX bus, see [[486DLC]].
<gallery mode="packed" heights="200">
Texas Instruments TX486SLC.jpg|TI486SLC
Evergreen Technologies Inc., 486 SuperChip (16118395508) (cropped).jpg|Cyrix Cx486SLC with 87SLC co-processor (top view)
Evergreen Technologies Inc., 486 SuperChip (16305942855) (cropped).jpg|Cyrix Cx486SLC with 87SLC co-processor (bottom view)
KL TI 486SXLC.jpg|TI486SXLC
</gallery>

== Versions ==
=== Cx486SLC/SLC2 ===
The base 486SLC, which had speeds of 20, 25, 33, and 40 MHz with 1 KB of cache and a 16-bit bus. A later version, the 486SLC2, ran at 50 MHz.
{| class="wikitable"
!Model
!Bus Speed
!Frequency
!Cache
!Voltage
!Notes
|-
|'''Cx486SLC-20'''
|20 MHz
|20 MHz
|1 KB
|5 V
|100-pin [[quad flat package]] (QFP).
|-
|'''Cx486SLC/E-V20'''
|20 MHz
|20 MHz
|1 kB
|3.3 V
|Advanced power management, low voltage, 100-pin QFP.
|-
|'''Cx486SLC-25MP'''
|25 MHz
|25 MHz
|1 kB
|5 V
|100-pin QFP.
|-
|'''Cx486SLC/E-25-MP'''
|25 MHz
|25 MHz
|1 kB
|5 V
|Advanced power management, 100-pin QFP.
|-
|'''Cx486SLC/E-25-QP'''
|25 MHz
|25 MHz
|1 kB
|5 V
|Advanced power management, 100-pin QFP.
|-
|'''Cx486SLC/E-V25MP'''
|25 MHz
|25 MHz
|1 kB
|3.3 V
|Advanced power management, low voltage, 100-pin QFP.
|-
|'''Cx486SLC-33MP'''
|33 MHz
|33 MHz
|1 kB
|5 V
|100-pin QFP.
|-
|'''Cx486SLC/E-33-MP'''
|33 MHz
|33 MHz
|1 kB
|5 V
|Advanced power management, 100-pin QFP.
|-
|'''Cx486SLC/E-40-MP'''
|40 MHz
|40 MHz
|1 kB
|5 V
|Advanced power management, 100-pin QFP.
|-
|'''Cx486SLC2-50'''
|25 MHz
|50 MHz
|1 kB
|5 V
|100-pin QFP.
|}

=== TI486SLC ===
TI's rebranded version of the Cx486SLC.
{| class="wikitable"
|+[https://archive.org/details/bitsavers_tiTI486199rReferenceGuide_13259023/page/n21/mode/2up?q=ti486slc&view=theater TI 486SLC/486DLC Reference Guide]
!Model
!Bus Speed
!Frequency
!Cache
!Voltage
!Notes
|-
|'''TI486SLC/E'''
|25 MHz
|25 MHz
|1 KB
|5 V
|Advanced power management, 100-pin [[Quad flat package|QFP]].
|-
|'''TI486SLC/E-33PAF'''
|33 MHz
|33 MHz
|1 KB
|5 V
|Advanced power management, 100-pin QFP.
|-
|'''TI486SLC/E-V'''
|25 MHz
|25 MHz
|1 KB
|3 V
|Advanced power management, low voltage, 100-pin QFP.
|}

=== TI486SXLC/SXLC2 ===
The TI486SXLC/SXLC was Texas Instrument's version of the Cx486SLC. They had 8 KB of cache over the original 1 KB, a 32-bit internal data bus, and supported clock-doubling.
{| class="wikitable"
|+[https://usermanual.wiki/Document/1994TI486SXLCandTI486SXLMicroprocessorsReferenceGuide.1822911953/view TI 486SXLC/486SXL Reference Guide]
!Model
!Bus Speed
!Frequency
!Cache
!Voltage
!Notes
|-
|'''TI486SXLC-V25-PJF'''
|25 MHz
|25 MHz
|8 kB
|3.3 V
|Low power version of SXLC, 100-pin [[Quad flat package|QFP]] for compatibility with 486SLC.
|-
|'''TI486SXLC-040-PJF'''
|20-40 MHz†
|40 MHz
|8 KB
|5V
|100-pin QFP for compatibility with 486SLC.
|-
|'''TI486SXLC2-050-PJF'''
|25 MHz
|50 MHz
|8 kB
|5 V
|100-pin QFP for compatibility with 486SLC.
|-
| colspan="6" |† - Can operate at nonclock-doubled 40 MHz or clock-doubled 20/40 MHz.
|}

=== Cx486SRx2 ===
{| class="wikitable"
|+[https://www.farnell.com/datasheets/100667.pdf Cx486DRx2/Cx486SRx2 Datasheet]
!Model
!Bus Speed
!Frequency
!Cache
!Voltage
!Notes
|-
|'''Cx486SRx2-25/50'''
|25 MHz
|50 MHz
|1 kB
|3.3 V
|Clip-on upgrade version of the SLC, compatible with the 386SX-16, 20, or 25 MHz.
|}

== Intel v. Cyrix lawsuit ==
Before even announcing the chip in March of 1992, Intel filed a lawsuit against Cyrix for patent infringement. Prior to this, Cyrix asked for a declaratory judgement that would prevent Intel from suing Cyrix.<ref name=":0" /> Texas Instruments joined the suit shortly after with an intervene, siding with Cyrix.<ref>{{Cite news|date=3 June 1992|title=TI asks to intervene in Cyrix-Intel suit|pages=37|work=[[Fort Worth Star-Telegram]]|url=https://www.newspapers.com/image/642973164/?terms=cyrix%20intel%20lawsuit&match=1|access-date=21 February 2022}}</ref>

Cyrix used SGS-Thomson as a second manufacturer of the chip, as the company had license to use Intel's patents. Intel however claimed the licence SGS-Thomson had was never intended to allow companies like Cyrix to circumvent Intel patents, which Intel stated was "patent laundering".<ref>{{Cite news|last=Pollack|first=Andrew|date=30 March 1992|title=New Rival For Intel's Key Chip|work=[[The New York Times]]|url=https://www.nytimes.com/1992/03/30/business/new-rival-for-intel-s-key-chip.html|access-date=15 February 2022}}</ref>

The lawsuit, which concluded in 1994, stated:<blockquote>''Cyrix is entitled to judgment in its favor on its affirmative defenses of patent exhaustion and implied license based on the use or resale of its claim 1 microprocessors purchased from TI and ST.''<ref>{{Cite web|date=21 January 1994|title=Cyrix Corp. v. Intel Corp., 846 F. Supp. 522 (E.D. Tex. 1994)|url=https://law.justia.com/cases/federal/district-courts/FSupp/846/522/1687321/|url-status=live|access-date=15 February 2022|website=[[Justia]]|archive-url=https://web.archive.org/web/20151002135814/http://law.justia.com/cases/federal/district-courts/FSupp/846/522/1687321/ |archive-date=2015-10-02 }}</ref></blockquote><blockquote></blockquote>

== See also ==
* '''[[Cyrix Cx486DLC]]''' - Cyrix's next CPU offering, released in June of 1992.

== References ==
<references />
*{{cite web|url=http://www.tweaktown.com/reviews/22/via_c3_aka_cyrix_3/index.html |title=VIA C3 (AKA Cyrix 3) |date= 5 July 2001 | website=TweakTown |archive-url=https://web.archive.org/web/20200729035127/https://www.tweaktown.com/reviews/22/via_c3_aka_cyrix_3/index.html |archive-date=29 July 2020}} Mentions Cyrix Cx486SLC in the Introduction.

[[Category:Cyrix x86 microprocessors|486SLC]]
[[Category:Computer-related introductions in 1992]]
[[Category:X86 microarchitectures]]