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Since I've been involved in the Acorn scene, a huge range of machines have come and gone. I first became a 'lifelong' Acorn fan when I bought a BBC B back in 1982. Since then, I've been developing software, helping to encourage the world-wide adoption of RISC OS (and hopefully destroy Microsoft in the process - I can dream!!) and offering support to RISC OS users the world over.

This page contains various 'legacy' information that I've removed from the main Comp.Sys.Acorn.* newsgroups FAQ which I maintain.

Acorn Graphics Capabilities

All the old Acorn machines were highly upgradeable so that many could achieve colour depths and resolutions beyond what is listed here.

The information listed here is the default capabilities of the machines as originally supplied by Acorn. As such it should be taken as a guide to the minimum abilities of the hardware.

8 bit machines

This covers the BBC Model B, BBC Model B+, Master 128 and ABC range of machines. The display hardware was based on the 6845CRTC chip and was highly flexible for it's time. Resolutions possible :-

X res. Y Res Colours
640    256     2
320    256     2,4
160    256     4,16

As well a Teletext character graphics mode and two text only modes were provided by default. The palette range was 16 colours with modes using less than 16 colours capable choosing any mix of the 16 colours, up to the number displayable of course, for display.

8 MHz ARM based machines

This is the original Archimedes range of machines and covers the A300 series, A400 series, R140 and A3000 machines. The increased capability of the VIDC1a chip dramatically enhanced the resolutions and colours depths possible, namely :-

X res. Y res. Colours
160    256    4,16,256
320    256    2,4,16,256
640    250    4,16
640    256    2,4,16,256
640    480    2,4,16,256
1056   250    16
1056   256    16,256
1152   896    2

As can be seen this quite a wide variety of default screen modes. Most are provided to allow driving the various kinds of monitors out there easier, since they are suited to that monitor. The palette range was 4096 colours (12 bit) but the VIDC1a only had 16 hardware palette registers. This meant that in screen modes with sixteen colours or less then the colours could be mapped to any of the 4096 available. However in 256 colour modes 4bits of the colour data are hardware derived and cannot be adjusted. The net result was in a 256 colour a block of 16 colours could be assigned as desired with that block of 16 covering a range of the 4096 available colours.

12 MHz ARM based machines

This covers the A3010, A3020, A4000, A4, A5000, A540 & R260 machines. Here the VIDC1a was still used but it had an extra oscillators added and the primary oscillator was faster (32 MHz) giving finer pixel resolutions. The extra oscillator provided true PC VGA style compatibility for monitors instead of a 24 MHz 'faked' version which sometimes caused problems with intolerant VGA monitors.

X res. Y res. Colours
160    256    4,16,256
320    256    2,4,16,256
640    200    2,4,16,256
640    250    16
640    256    2,4,16,256
640    352    2,4,16,256
640    480    2,4,16,256
640    512    2,4,16,256
768    288    2,4,16,256
800    600    2,4,16
800    352    2,4,16,256
1056   250    16
1056   256    16,256
1152   896    2

Because the display hardware was essentially the same as the 8MHz machines' the palette handling was identical.

Risc PC machines

This covers all machines in the Risc PC 600, Risc PC 700, A7000 & A7000+ ranges. Here the newer VIDC20 chip has been used and the display capabilities are somewhat extended. Namely :-

X res. Y res. Colours
160    256    4,16,256
320    256    2,4,16,256
640    200    2,4,16,256
640    250    4,16
640    256    2,4,16,256
640    352    2,4,16,256
640    480    2,4,16,256
640    512    2,4,16,256
768    288    2,4,16,256
800    600    2,4,16,256,32k*,16M**
896    352    2,4,16,256
1024   768    16,256*,32k**
1056   250    16
1056   256    16,256
1152   896    2
1280   1024   4,16*,256**
1600   1200   16*,256** 
* Requires 1 MB of VRAM
** Requires 2 MB of VRAM

With the addition of Video RAM (VRAM) to the Risc PC the base capabilities are a touch variable, thus the note next to some of entries.

All other modes are available with standard DRAM, and these the only modes the A7000 can access. The A7000+, thanks to it's faster memory speeds, functions equivalently to a RiscPC with 1 Mb of VRAM even though it doesn't have any VRAM itself.

Furthermore the new VIDC20 has 256 palette registers, compared to the VIDC1a's 16, and a palette range of 16 million colours. Exactly how the colour mapping in 32,000 modes is handled is not yet clear. Again these are just standard screen modes provided, and even perhaps not all of them - the Risc PC is completely configurable in display resolutions and capabilities.

For graphics capabilities of current machines, please see the CSA.* FAQ (Question 1.10).

What are the memory limits of the various Acorn machines?

For the most part the 8 bit machines were limited to a maximum of around 256k of memory. Although various expansion systems including second processors effectively meant the upper limit was about 1 Meg. (Although I have been told of a second processor with 4 Meg of memory in it. ) For the early 32 bit machines the upper limit currently is 16 Meg of memory. Not all of the range of machines are capable of this however and the list looks something like this:-

A3xx - 8 MB maximum through third party, 1 MB official limit. 
A4xx - 8 MB maximum through third party, 4 MB official limit. 
A4xx/I - 8 MB maximum through third party, 4 MB official limit. 
A3000 - 8 MB maximum through third party, 2 MB official limit. 
A540/R260/R225 - 16 MB maximum. 
A5000 - 8 MB maximum through third party, 4 MB official limit. 
A4 - 4 MB official limit. 
A30x0 - 4 MB official limit. 
A4000 - 4 MB official limit. 
A5000 - 8 MB official limit. (alpha variant of the A5000) 
A7000 - 128 MB + memory on mother board. (Tops out at 132 MB and requires a 128 MB SIMM to do it.)

Newer RiscPC machines have an official upper limit of 256MB, plus 2MB of VRAM on all models. However this does require you using 128MB SIMMS.

If you add the Kinetic StrongARM upgrade (available from Castle Technology) then this upper limit can be expanded further because the Kinetic card contains either 64MB or 128MB SDRam on board. Further information on the Kinetic card is available from Castle Technology (www.castle-technology.co.uk/castle/front.shtml).

If you have RISC OS 4.39 or later you can upgrade Kinetic cards to 256MB

See Q3.13 in the Comp.Sys.Acorn.* FAQ for memory specifications.

Acorn Diversification

Acorn, around October 1995, restructured itself into separate companies. Consequently the originating company will be noted by the machine model name, in brackets, from here on down.

A list of current RISC OS machines is available in the main FAQ, Q1.2

Network Computer (Acorn Network Computing)

is the production implementation of the Reference Standard that Oracle commissioned Acorn to specify for Network Computers. In common with the philosophy the default NC does not have any storage devices beyond a smart card, but can be upgraded as required by the customer. Launched August 1996.

4096k Memory (expandable to 16384kb)
IP Stack by default, capable of using extra drives as required.
Smartcard interface by default.
ARM 7500FE processor. (40 MHz)
12 MHz RAM.
4096k OS in ROM.
~35.9 MIPS.

Set Top Box 2 (Online Media)

an advanced networked computer designed to provide an interactive TV station in the home. These machines require high capacity networks to operate and as such are, as of early 1997, limited mostly to trials in selected areas. These machines feature hardware MPEG decoders as well as an infrared remote for controlling it.

Strictly speaking these machine are no longer quite computers but are more converging into versatile home appliances. Launched July 1996.

2048k Memory (expandable to 32768kb)
CDFS by default.
Optional CDROM drive.
ARM 7500FE processor. (32 MHz)
12 MHz RAM.
4096k OS in ROM.
~28.7 MIPS.

Stork (Acorn Risc Technologies)

the successor to the A4 this is effectively a RiscPC in portable form. There are a few improvements over the capabilities of the RiscPC range including a PCMCIA interface. It is unique in being the first Acorn portable to offer a docking station arrangement. Not launched initially as a product it has been more a licensable design available for volume customers to order as required. A by product of this is that design is somewhat mutable featuring at least two types of LCD screen chosen as required by the customer.

The design has been available since mid 1996.

8192Kb Memory (expandable to 256Mb)
ADFS by default.
IDE interface. (425 Mb)
ARM 7500 processor. (32 MHz)
12 MHz RAM.
4096k OS in ROM.
~29 MIPS.

NewsPAD (Acorn Risc Technologies)

perhaps the most unusual of the portable offerings from ART this is a graphics tablet arrangement of portable with no integral keyboard offered. Rather input is through an inbuilt touchscreen overlayed on the colour LCD display. Two PCMCIA slots are available along with 496 bytes of non-volatile RAM, compared with the more usual 240 bytes offered. A docking station provides parallel, external monitor, serial, keyboard and mouse ports along with a floppy disc drive.

Available since Mid 1996.

8192Kb Memory (expandable to 256Mb)
ADFS by default.
IDE interface. (420 Mb)
ARM 7500 processor. (40 MHz)
12 MHz RAM.
4096k OS in ROM.
~35.9 MIPS.

StrongARM RiscPC (Acorn Risc Technologies)

basically the 700 series machine with larger hard drives, RISC OS 3.7 and a StrongARM (202 MHz) in them. Released September 1996.

Acorn Reunification

As part of an image strengthening procedure Acorn reconsolidated to present one company image to the world. Therefore the machines below will simply be referred to as 'Acorn' machines now.

A7000+ is an updated version of the 'entry level' A7000 machine, as the name implies. Keeping the same styling as the A7000 it is notable especially for two features. The presence of a hardware floating point processor by default and the ability to use EDO RAM. Both are firsts for Acorn equipment and hopefully signal a trend in Acorn's design priorities.

Launched 18th of May 1997 at the Wakefield Show. It is still available, now manufactured by Castle Technology

24Mb EDO Memory (expandable up to 136Mb)
ADFS by default.
IDE interface. (20 Gb hard drive)
ARM 7500 FE processor. (48 MHz)
32 MHz RAM.
4096k OS in ROM.
~43.08 MIPS.

StrongARM RiscPC (Alpha variant) basically the same as it's earlier incarnation but with a 233 MHz StrongARM in it rather than a 202 MHz one.
Released 10th September 1997. (see above for more information on current models)

CoNCord , an uprated NC this is a StrongARM powered machine with expanded memory and Java built in by default. In a break with previous NC designs a Tower configuration has been used with a custom rounded case. Like other NC designs the CoNCord features a ROMCard interface for upgrading the OS as required and an infra-red interface for armchair control.
Launched 7th October 1997.

4096k Memory. (Expandable to 256 Mb, comes with 2 Mb VRAM as well)
IP Stack by default, capable of using extra drives as required.
Smartcard interface by default.
Digital SA110 processor. (233 MHz)
16 MHz RAM.
8192k OS in ROM.
~233 MIPS.

The A7000+

The A7000+ was manufactured by Castle Technology and was an ideal entry model to introduce users to RISC OS.

There were four models in the range, starting with a 16MB model running RISC OS 3.7 originally priced at £399.00+VAT.

24Mb EDO Memory (expandable up to 136Mb)
ADFS by default.
IDE interface. (20 Gb hard drive)
ARM 7500 FE processor. (48 MHz)
32 MHz RAM.
4096k OS in ROM.
~43.08 MIPS.

The Risc Station series

After the demise of Acorn, this was one of the new RISC OS based machines designed around non-Acorn hardware. Risc Stations were available in Network, Lite, Lite+ and 'Scorcher' models. A more powerful model - the Risc Station Evolution - was being developed, but sadly never saw the light of day.

For more information, contact Risc Station Ltd at 168 Elliott Street, Tyldesley, Manchester, M29 8DS (tel.+44(0)1942 797777, fax +44(0)1942 797711). Web: http://www.riscstation.co.uk - email: info@riscstation.co.uk

Detailed specification comprises;

Risc Stations are based upon a 56MHz ARM7500FPE (with integrated floating point co-processor) with RISC OS 4 fitted as standard. Notable features of the base system include:

8Mb 60ns EDO memory, upgradeable to 256Mb.
Screen resolution up to 1600x1200x256 colours.
6Mb Flash memory containing RISC OS 4 and additional utilities.
PS2 style keyboard and PS2 3 button mouse input.
2 x fast serial ports rated at 460K baud.
2 x high speed EIDE ports.
2 x PC style game ports with MIDI.
10baseT ethernet port with Wake On Lan.
EPP/ECP fast parallel port.
IRDA infra-red interface support.
High density floppy drive port
15 pin VGA connector.
Full 16 bit OPL3 stereo sound sampler & mixer with FM synthesiser
MIDI
Wavetable support and 2 CD mixer ports.
3 x 3.5mm jack sockets for Line in/Mic in/Headphone & speaker out.

Machine differences
neTworx
As base system above.
 
neTworxHD
As base system, plus 2GB (min) hard drive.
 
R7500 Lite
As base system, plus 16Mb memory, 4.3GB EIDE hard drive, 48x Atapi EIDE CD Rom Drive.
 
R7500+ Lite
As base system, plus 64Mb memory, 10.1GB EIDE hard drive, 52x Atapi EIDE CD Rom Drive.
 
R7500 Scorcher
As R7500+ Lite, plus CD-RW, native support for LS120 & ZIP atapi drives, 60W external speakers.

The Microdigital series

Microdigital were another third-party manufacturer who produced a range of RISC OS based desktop computers, based on ARM RISC processors.

Their full range of products used to be on their website at http://www.microdigital.co.uk/products/ but Microdigital are no longer trading.

The Omega

Full specs are available from the Microdigital web site at http://www.microdigital.co.uk/ompg1.htm

Second Processors

What is a second processor and what second processors are there?

A second processor was the generic name for a range of parasite processors that could be linked to Acorn's original 8 bit machines via what was called the `Tube` interface. Basically the host machine became dedicated to handling the Input and Output while the second processor would do the higher level functions (like running your programs). The second processor ran asynchronously to the host processor allowing incredible increases in execution speed for programs. A wide range of processors were supported this way allowing Acorn's eight bit range of machines to remain viable and useful for much longer than their technology would suggest.

The Second Processors that existed were :-

Z80 second processor.
6 MHz RAM.
64k Memory.
CP/M OS.
External second processor for all eight bit machines.

* 6502 second processor.
3 MHz RAM.
64k Memory.
Extended version of the BBC MOS.
External processor for all eight bit machines.

32016 second processor.
6 MHz RAM.
256k-4096k Memory.
Panos.
External processor for all eight bit machines.

ARM 1 second processor.
4 MHz RAM. (At a guess...)
4096k Memory.
Brazil OS.
External processor for all eight bit machines.

6502 co-processor. (internal second processor)
4 MHz RAM.
64k Memory.
Extended version of BBC MOS.
Internal processor for Master 128 machines but could be fitted external to the other eight bit machines.

80186 co-processor.
10 MHz RAM.
512k Memory.
DR-DOS+ with GEM.
Internal processor for Master 128 machines but could be fitted external to the other eight bit machines.

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 Last edit: 13th Feb 2012 at 8:24pm (801 days ago)

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