Editing Floating-point unit (section)

== Add-on FPUs ==
{{Main|Coprocessor}}
Several models of the [[PDP-11]], such as the PDP-11/45,<ref>{{cite book|url=http://bitsavers.org/pdf/dec/pdp11/handbooks/PDP1145_Handbook_1973.pdf|title=PDP-11/45 Processor Handbook|at=Chapter 7 "Floating Point Processor"|date=1973|publisher=[[Digital Equipment Corporation]]}}</ref> PDP-11/34a,<ref name="1979-pdp-11-handbook">{{cite book|url=http://bitsavers.org/pdf/dec/pdp11/handbooks/PDP11_Handbook1979.pdf|title=PDP-11 Processor Handbook|date=1979|publisher=[[Digital Equipment Corporation]]}}</ref>{{rp|pages=184–185}} PDP-11/44,<ref name="1979-pdp-11-handbook" />{{rp|pages=195,211}} and PDP-11/70,<ref name="1979-pdp-11-handbook" />{{rp|pages=277,286–287}} supported an add-on floating-point unit to support floating-point instructions. The PDP-11/60,<ref name="1979-pdp-11-handbook" />{{rp|page=261}} MicroPDP-11/23<ref name="micro-PDP-11-handbook">{{cite book|url=http://bitsavers.org/pdf/dec/pdp11/handbooks/EB-24944-18_Micro_PDP-11_Handbook_1983-84.pdf|title=MICRO/PDP-11 Handbook|page=33|date=1983|publisher=[[Digital Equipment Corporation]]}}</ref> and several [[VAX]] models<ref>{{cite book |url=http://bitsavers.org/pdf/dec/vax/handbook/VAX_Hardware_Handbook_Volume_1_1986.pdf |title=VAX – Hardware Handbook Volume I – 1986 |date=1985 |publisher=[[Digital Equipment Corporation]] |language=en-us}}</ref><ref>{{cite book |url=http://bitsavers.org/pdf/dec/vax/handbook/VAX_Hardware_Handbook_Volume_2_1986.pdf |title=VAX – Hardware Handbook Volume II – 1986 |date=1986 |publisher=[[Digital Equipment Corporation]] |language=en-us}}</ref> could execute floating-point instructions without an add-on FPU (the MicroPDP-11/23 required an add-on microcode option),<ref name="micro-PDP-11-handbook" /> and offered add-on accelerators to further speed the execution of those instructions.

In the 1980s, it was common in [[IBM PC]]/compatible [[microcomputers]] for the FPU to be entirely separate from the [[Central processing unit|CPU]], and typically sold as an optional add-on. It would only be purchased if needed to speed up or enable math-intensive programs.

The IBM PC, [[IBM Personal Computer XT|XT]], and most compatibles based on the 8088 or 8086 had a socket for the optional 8087 coprocessor. The [[IBM Personal Computer/AT|AT]] and [[Intel 80286|80286]]-based systems were generally socketed for the [[x87#80287|80287]], and [[Intel 80386|80386/80386SX]]-based machines{{snd}}for the [[x87#80387|80387]] and [[Intel 80387SX|80387SX]] respectively, although early ones were socketed for the 80287, since the 80387 did not exist yet. Other companies manufactured co-processors for the Intel x86 series. These included [[Cyrix]] and [[Weitek]]. [[Acorn Computers]] opted for the WE32206 to offer [[Single-precision floating-point format|single]], [[Double-precision floating-point format|double]] and [[extended precision]]<ref>{{cite web |title=Western Electric 32206 co-processor |url=https://www.cpu-world.com/CPUs/32206/index.html |website=www.cpu-world.com | access-date=2021-11-06}}</ref> to its [[ARM architecture|ARM]] powered [[Acorn Archimedes|Archimedes]] range, introducing a gate array to interface the ARM2 processor with the WE32206 to support the additional ARM floating-point instructions.<ref name="abcomputing199003_arm">{{ cite magazine | title=Programming The ARM: The Floating Point Co-processor | magazine=A&B Computing | last1=Fellows | first1=Paul | date=March 1990 | pages=43–44 }}</ref> Acorn later offered the FPA10 coprocessor, developed by ARM, for various machines fitted with the ARM3 processor.<ref name="acorn_fpa10">{{ cite press release | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/PR/FPA_release.txt | title=Acorn Releases Floating Point Accelerator | publisher=Acorn Computers Limited | date=5 July 1993 | access-date=7 April 2021 }}</ref>

Coprocessors were available for the [[Motorola 68000 series|Motorola 68000 family]], the [[Motorola 68881|68881 and 68882]]. These were common in [[Motorola 68020]]/[[Motorola 68030|68030]]-based [[workstation]]s, like the [[Sun-3]] series. They were also commonly added to higher-end models of Apple [[Macintosh]] and Commodore [[Amiga]] series, but unlike IBM PC-compatible systems, sockets for adding the coprocessor were not as common in lower-end systems.

There are also add-on FPU coprocessor units for [[microcontroller]] units (MCUs/μCs)/[[single-board computer]] (SBCs), which serve to provide floating-point [[arithmetic]] capability. These add-on FPUs are host-processor-independent, possess their own programming requirements ([[Mathematical operation|operations]], [[instruction set]]s, etc.) and are often provided with their own [[integrated development environment]]s (IDEs).