Editing Acorn Archimedes (section)

=== A300 and A400 series ===
{{anchor|A300|A310}}

Powered by an [[ARM architecture#ARM2|ARM2]] (Acorn RISC Machine) processor, the Acorn Archimedes was variously described as "the first [[Reduced instruction set computer|RISC]] machine inexpensive enough for home use",<ref name="pountain198710">{{cite magazine | url=https://archive.org/details/byte-magazine-1987-10-rescan/1987_10_BYTE_12-11_Heuristic_Algorithms/page/n130/mode/1up | title=The Archimedes A310 | magazine=BYTE | date=October 1987 | access-date=4 August 2014 | author=Pountain, Dick | pages=125}}</ref> and "the first commercially-available RISC-based microcomputer". The first models were released in June 1987, as the 300 and 400 series.<ref name="popcompweekly19870626">{{cite magazine | url=https://archive.org/details/popular-computing-weekly-1987-06-26/page/n5/mode/1up | title=Acorn RISCs it | magazine=Popular Computing Weekly | date=26 June 1987 | access-date=28 March 2021 | pages=6}}</ref> The 400 series included four expansion slots and an [[ST-506]] controller for an internal [[hard drive]], whereas the 300 series required the addition of a backplane to gain expansion slot capabilities. A two slot [[backplane]] could be added to the 300 series as an official upgrade, with the possibility of 4-slot backplane being available from third parties, but a hard drive expansion card was also required for these machines, occupying one slot.<ref name="acornuser198809_hardware">{{ cite magazine | url=https://archive.org/details/AcornUser074-Sep88/page/n72/mode/1up | title=Do It The Hard Way | magazine=Acorn User | date=September 1988 | access-date=30 June 2022 | last1=Watkins | first1=David | pages=71, 73, 75 }}</ref>

Both series included the [[Arthur (operating system)|Arthur operating system]] (later replaced by [[RISC OS]] as a paid-for upgrade), [[BBC BASIC]] programming language, and an [[emulator]] for Acorn's earlier [[BBC Micro]], and were mounted in two-part cases with a small central unit, [[Computer display|monitor]] on top, and a separate [[Computer keyboard|keyboard]] and three-button [[computer mouse|mouse]] (the middle one used for pop-up [[context menu]]s of the operating system). All models featured eight-channel 8-bit [[stereo sound]] and were capable of displaying [[8-bit color|256 colours]] on screen.<ref name="introduction" />{{rp|pages=4}}<ref name="vidc_datasheet">{{Cite web|url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/Misc/Acorn_VIDC_Datasheet.pdf|title=VIDC (Video Controller) datasheet}}</ref>{{rp|pages=2}}

Three models were initially released with different amounts of memory, the A305, A310 and A440.<ref name="introduction">{{cite tech report | url=http://chrisacorns.computinghistory.org.uk/docs/Acorn/Misc/AcornTraining_IntroToArc.pdf | title=Introduction to Archimedes | publisher=Acorn Computers Limited | access-date=28 February 2021 | pages=4 | quote=The particular models available were the A305 and A310, with 0.5 MB and 1 MB of RAM respectively, and the A440, with 4 MB of RAM.}}</ref> The 400 series models were replaced in 1989 by the A410/1, the A420/1 and A440/1,<ref name="acornuser198906a">{{ cite magazine | url=https://archive.org/details/AcornUser083-Jun89/page/n8/mode/1up | title=Acorn back home with new micro | magazine=Acorn User | date=June 1989 | access-date=27 March 2021 | pages=7}}</ref> these featuring an upgraded MEMC1a and RISC OS. Earlier models which shipped with Arthur could be upgraded to {{nowrap|RISC OS 2}} by replacing the [[read-only memory|ROM]] chip containing the operating system.<ref name="acornuser198902_riscos" /> Because the ROM chips contained the operating system, the computer [[booting|booted]] instantly into its GUI system, familiar from the [[Atari ST]].<ref name="pcw198506_atarist">{{ cite magazine | url=https://archive.org/details/PersonalComputerWorld1985-06/page/136/mode/2up | title=Atari 520ST | magazine=Personal Computer World | date=June 1985 | access-date=29 July 2021 | last1=Bright | first1=Peter | pages=136–138, 140, 142 }}</ref>{{rp|pages=140|quote=Unlike most other disk-based machines both the DOS and the front end are contained in ROM. This allows the machine to go directly into its operating system on start-up without having to read from disk.}}

Despite the A310 being limited to 1&nbsp;MB of RAM officially,<ref name="archive198903b" /> several companies made upgrades to 2&nbsp;MB and 4&nbsp;MB, with the smaller upgrades augmenting the built-in RAM and the larger upgrades replacing it entirely.<ref name="acornuser199204_memory">{{ cite magazine | url=https://archive.org/details/AcornUser117-Apr92/page/n92/mode/1up | title=Memory Lapse | magazine=Acorn User | date=April 1992 | access-date=30 May 2021 | last1=Brown | first1=Malcolm | pages=91–92 }}</ref> The 400 series were officially limited to 4&nbsp;MB of RAM, but several companies released 8&nbsp;MB upgrades that provided an extra MEMC chip plus 4&nbsp;MB of RAM to complement an existing 4&nbsp;MB of fitted RAM.<ref name="acornuser199108_8mb">{{ cite magazine | url=https://archive.org/details/AcornUser109-Aug91/page/n117/mode/2up | title=Mega Memory | magazine=Acorn User | date=August 1991 | access-date=4 June 2021 | last1=Carrion | first1=Tom | pages=116–117 }}</ref>