Editing Acorn Archimedes (section)

==== Graphics expansions ====

An expansion to speed up the VIDC chip in the Archimedes from 24&nbsp;MHz to 36&nbsp;MHz was announced by Atomwide in 1990, offering higher resolution display modes for machines connected to multisync monitors.<ref name="acornuser199006_atomwide">{{ cite magazine | url=https://archive.org/details/AcornUser095-Jun90/page/n8/mode/1up | title=Atomwide Enhancers | magazine=Acorn User | date=June 1990 | access-date=10 May 2021 | pages=7 }}</ref> Although resolutions up to {{nowrap|1280 x 480}} and {{nowrap|1024 x 640}} were supported, flicker due to a decreased refresh rate was reported as a problem, with {{nowrap|1152 x 486}} appearing to be more comfortable in this regard. The SVGA resolution of {{nowrap|800 x 600}} was also supported in up to 16 colours.<ref name="riscuser199101_vidc">{{ cite magazine | url=https://archive.org/details/eu_RiscUser_1991-0102A_OCR/page/n29/mode/2up | title=Making the Most of Your Multi-Sync Monitor | magazine=RISC User | date=January 1991 | access-date=10 May 2021 | last1=Spencer | first1=David | last2=Thorpe | first2=Martin | pages=30–31 }}</ref> One side-effect of increasing the frequency of the VIDC was to also increase the frequency of generated sounds, since the VIDC was also responsible for sound generation.<ref name="archive199007_vidc">{{ cite magazine | url=https://archive.org/details/Archive_1990-07_OCR/page/n22/mode/1up | title=Atomwide VIDC Enhancer | magazine=Archive | date=July 1990 | access-date=10 May 2021 | last1=Ward | first1=John | pages=21–23 }}</ref> VIDC enhancers were supplied by some monitor vendors together with the appropriate cable for Archimedes machines, although fitting the device still required approved service work to be performed. Monitors such as the Taxan 795 Multivision were only usable in multisync modes without the VIDC enhancer whose accompanying software sought to "redefine all modes" to be compatible with the display as well as providing new modes.<ref name="acornuser199012_multivision">{{ cite magazine | url=https://archive.org/details/AcornUser101-Dec90/page/n120/mode/1up | title=Multivision Magic | magazine=Acorn User | date=December 1990 | access-date=12 May 2021 | last1=James | first1=Paul | pages=119 }}</ref>

One drawback of VIDC enhancer solutions was the increased memory bandwidth used by the VIDC at its newly elevated frequency, slowing down machines when using higher resolution modes, particularly machines with ARM2 processors and slower memory busses. Consequently, other solutions were adopted to work around the limitations of the built-in display hardware, notably "graphics enhancers" such as the PCATS graphics enhancer from The Serial Port,<ref name="acornuser199107_pcats">{{ cite magazine | url= https://archive.org/details/AcornUser108-Jul91/page/n104/mode/1up | title=Good Looking | magazine=Acorn User | date=July 1991 | access-date=15 May 2021 | last1=Williams | first1=Simon | pages=103 }}</ref> and "colour cards" such as Computer Concepts' ColourCard and State Machine's G8 which provided a separate framebuffer, holding a copy of the normal screen memory, for use in generating a video signal independently of the system's main memory. This permitted higher refresh rates (up to 70&nbsp;Hz) even for higher resolution modes, although the maximum size of the screen memory imposed by the VIDC ({{nowrap|480 KB}}) also imposed a limit on available resolutions and colour depths, with {{nowrap|800 x 600}} being the highest resolution 256 colour mode that could be supported. However, such cards were also able to support more flexible palettes in 256 colour modes than the VIDC, and for lower resolutions, greater colour depths offering over 32,000 colours could be supported.<ref name="acornuser199301_colourcards">{{ cite magazine | url=https://archive.org/details/AcornUser126-Jan93/page/n62/mode/1up | title=More than a shade better | magazine=Acorn User | date=January 1993 | access-date=3 March 2021 | last1=Bell | first1=Graham | pages=61–63 }}</ref> The ColourCard was reported to allow an ARM2 system to use a {{nowrap|1600 x 600}} display mode with 16 colours (occupying 480&nbsp;KB) with an operating speed of "160% of the speed of the considerably lower resolution Acorn mode 28", this being {{nowrap|640 x 480}} with 256 colours (occupying 300&nbsp;KB).<ref name="archimedean1993">{{ cite magazine | url=https://archive.org/details/Archimedean_Issue_7_1993_Computer_Concepts_GB/page/n9/mode/1up | title=ColourCard ...even better! | magazine=The Archimedean | date=1993 | access-date=19 May 2021 | pages=10 }}</ref>

State Machine, founded by former hardware designers from Computer Concepts and Watford Electronics,<ref name="acornuser199208_statemachine">{{ cite magazine | url=https://archive.org/details/AcornUser121-Aug92/page/n14/mode/1up | title=24-Bit Colour at BAU Show | magazine=Acorn User | date=August 1992 | access-date=8 February 2022 | pages=13 }}</ref> announced a range of colour card peripherals, starting with the G8 and G8+ in late 1992,<ref name="acornuser199210_statemachine">{{ cite magazine | url=https://archive.org/details/AcornUser123-Oct92/page/n18/mode/1up | title=New Card | magazine=Acorn User | date=October 1992 | access-date=3 August 2021 | pages=15 }}</ref> followed by the G8 Professional, these cards being demonstrated at the BBC Acorn User show in 1992, as was the Computer Concepts ColourCard.<ref name="acornuser199212_colourcards">{{ cite magazine | url=https://archive.org/details/AcornUser125-Dec92/page/n8/mode/1up | title=Colour Cards Arrive at Show | magazine=Acorn User | date=December 1992 | access-date=3 August 2021 | pages=7 }}</ref> One potentially significant difference between the different product ranges was the role of the VIDC, with the ColourCard employing a "video switch" that permitted the VIDC to generate an output signal independent of the card for traditional display modes, with the card only generating output for enhanced modes, whereas the State Machine cards were entirely responsible for output and thereby provided emulations of the traditional modes, this leading to a "letter-box" effect for some modes in early versions of the State Machine software and also causing compatibility issues with software, particularly games, that accessed VIDC registers directly to configure the display.<ref name="archimedesworld199310_vidc">{{ cite magazine | url=https://archive.org/details/acorn-archimedes-world-oct-1993/page/41/mode/1up | title=VIDC killed the video star | magazine=Archimedes World | date=October 1993 | access-date=26 August 2021 | pages=41–43 }}</ref> Subsequent developments from State Machine brought the G16 card, offering application-specific support for 15 and 16 bits per pixel modes.<ref name="acornuser199308_statemachine">{{ cite magazine | url=https://archive.org/details/AcornUser133-Aug93/page/n10/mode/1up | title=State Machine Sends Cards | magazine=Acorn User | date=August 1993 | access-date=4 August 2021 | pages=9 }}</ref>

Alongside bandwidth constraints, a fundamental limitation to the size of VIDC framebuffers was imposed by the memory controller, limiting the size of framebuffers transferred to the VIDC through [[Direct memory access|DMA]] to a specific 512&nbsp;KB physical memory region.<ref name="acorn_memc">{{ cite book | url=https://archive.org/details/memc_datasheet_sep86/page/n39/mode/1up | title=MEMC Datasheet | publisher=Acorn Computers Limited | date=30 September 1986 | volume=1 | access-date=11 September 2021 | isbn=1852500255 | pages=72 | quote=The DMA Address Generators can only address 512kBytes }}</ref> State Machine's ColourBurst card, announced together with its G16 card, employed memory mapping techniques to provide 1&nbsp;MB of video RAM instead of the 512&nbsp;KB of earlier cards and thus supporting larger screen modes.<ref name="acornuser199308_statemachine" /> The ColourBurst was, when reviewed in late 1993, the first 24-bit colour card available for the Archimedes, also supporting various upgrades including the "video switch" capability absent from earlier cards, PAL encoding, and other professional capabilities.<ref name="archimedesworld199310_colourburst">{{ cite magazine | url=https://archive.org/details/acorn-archimedes-world-oct-1993/page/44/mode/2up | title=Card Watch | magazine=Archimedes World | date=October 1993 | access-date=26 August 2021 | last1=Carlisle | first1=Chris | pages=44–46 }}</ref>

Coincidentally, ARM Limited announced the VIDC20—the successor to the VIDC10 in the Archimedes—at around the same time as the introduction of the Computer Concepts and State Machine product ranges in late 1992.<ref name="acornuser199212_vidc20">{{ cite magazine | url=https://archive.org/details/AcornUser125-Dec92/page/n8/mode/1up | title=VIDC20 Announced | magazine=Acorn User | date=December 1992 | access-date=3 August 2021 | pages=7 }}</ref> By late 1993, rumours about Acorn's next-generation system (eventually released as the Risc PC), particularly 24-bit colour support, led to suggestions of improved support for higher colour depths in RISC OS, accompanied by the observation in the context of State Machine's ColourBurst card that "it seems unlikely that another manufacturer will release such a powerful device before the launch of Acorn's new baby".<ref name="archimedesworld199310_colourburst" /> In late 1993, Computer Concepts announced the ColourCard Gold, developed in conjunction with Acorn to offer 15 bits per pixel support in the desktop environment. Meanwhile, State Machine announced the ClusterCard for 33&nbsp;MHz A5000 models, plugging into the memory controller socket and supporting upgrades to 8&nbsp;MB of RAM alongside graphics enhancements offering 1&nbsp;MB or 2&nbsp;MB of video RAM.<ref name="acornuser199401_graphics">{{ cite magazine | url=https://archive.org/details/AcornUser138-Jan94/page/n16/mode/1up | title=Graphics cards galore | magazine=Acorn User | date=January 1994 | access-date=4 August 2021 | pages=17 }}</ref> The ClusterCard, employing the G335 Cluster Module was reported to be the first graphics card for the Archimedes series not requiring the use of the VIDC.<ref name="acornuser199402_clustercard">{{ cite magazine | url=https://archive.org/details/AcornUser139-Feb94/page/n16/mode/1up | title=Cluster Card news | magazine=Acorn User | date=February 1994 | access-date=4 August 2021 | pages=17 }}</ref>

With IBM PC compatible systems leaving the Archimedes "well behind the competition in the display stakes", the ClusterCard was seen as attempting a solution similar to a [[VESA Local Bus|local bus]] architecture on the A5000, with the potential to "transform the A5000 into a serious graphics machine, with possibly as good a display potential as the next Acorn series equipped with VIDC20s".<ref name="acornuser199403_cards">{{ cite magazine | url=https://archive.org/details/AcornUser140-Mar94/page/n37/mode/2up | title=All on the cards | magazine=Acorn User | date=March 1994 | access-date=4 August 2021 | last1=Kreindler | first1=Jack | pages=38–40 }}</ref> The launch of the Risc PC in 1994 demonstrated Acorn's successor to the Archimedes, to which State Machine responded with a product called ColourView, "an all-new replacement for the original G8 and G16 State Machine graphics cards", offering 16 bits per pixel desktop-compatible screen modes, with a modular version also available for the ClusterCard without the 1&nbsp;MB framebuffer. The full version of the card was reportedly available for A300 series, A400 series, A5000 and A540 machines.<ref name="acornuser199406_colourview">{{ cite magazine | url=https://archive.org/details/AcornUser143-Jun94/page/n12/mode/1up | title=Next Generation of Graphics Card | magazine=Acorn User | date=June 1994 | access-date=4 August 2021 | pages=13 }}</ref>

Somewhat distinct from general graphics enhancements, various products were also introduced to support the broadcasting industry and other professional imaging applications. In late 1990, Millipede Electronic Graphics announced an imaging product called APEX (Archimedes P3 Expansion) featuring "four P3 (pixel pipeline processor) chips, together with an Arm3 processor running at 27&nbsp;MHz". With support for "broadcast quality graphics at 32 bits per pixel", hardware support for windows and sprites, emphasising real-time image combination and manipulation, the product was aimed at professional users and priced accordingly, with the version providing 4&nbsp;MB of RAM projected to cost £2750. Nevertheless, a licensing agreement had been reached with Acorn to "enable Risc OS graphics functions to be fully emulated".<ref name="acornuser199012_apex">{{ cite magazine | url=https://archive.org/details/AcornUser101-Dec90/page/n10/mode/1up | title=The New APEX Podule | magazine=Acorn User | date=December 1990 | access-date=4 August 2021 | pages=9 }}</ref> Following up from this earlier product, Millipede offered an "all new Apex Imager" video card in early 1994 featuring the four custom chips, ARM3, FPA, and 16&nbsp;MB of video RAM on a double-width podule costing £3975, this being virtually unchanged from the pricing of the original product from 1990.<ref name="acornuser199401_apex">{{ cite magazine | url=https://archive.org/details/AcornUser138-Jan94/page/n16/mode/1up | title=Video cards deluxe | magazine=Acorn User | date=January 1994 | access-date=4 August 2021 | pages=17 }}</ref> This product appears to make extensive use of FPGA devices and offers numerous video input and output facilities.<ref name="cch_apex_imager">{{ cite web | url=http://www.computinghistory.org.uk/det/24771/Apex-Imager-P3-Issue-4/ | title=Apex Imager P3 Issue 4 | website=Centre for Computing History | access-date=4 August 2021 }}</ref> Apex hardware was used by the [[Square Enix Europe#Eidos Interactive|Eidos]] video capture and compression solution, Thumper, which ran on a Risc PC and was able to process "MPEG 1 resolution video at full PAL frame rate in real time", being regarded in early 1995 as "the best digitiser for our needs on any platform" by Eidos' managing director.<ref name="acornuser199501_apex">{{ cite magazine | url=https://archive.org/details/AcornUser151-Jan95/page/n42/mode/1up | title=Making movies | magazine=Acorn User | date=January 1995 | access-date=29 October 2021 | last1=Kriendler | first1=Jack | last2=Streater | first2=Stephen B. | pages=43–45 }}</ref> Previous Eidos capture solutions used A540 machines with 8&nbsp;MB of RAM.<ref name="acornusr199308_eidos" />