Acorn Archimedes

Also of interest is an archived technical introduction to the Archimedes A305:

To give an idea of what Archimedes computers were capable of have a watch of this video on early 3D games for the system:

Please note that some images on this page can also be downloaded from the bottom of the page for better viewing.

Acorn A3000 Microcomputer

Acorn computers had developed for the BBC microcomputer (see BBC Micro Second Processors page) a second processor add on featuring their new processor, the ARM chip. The Archimedes range of computers from Acorn, which followed the BBC micro series, were the first computers to use an ARM chip as the main CPU.

Formally titled 'BBC A3000', the A3000 is an Archimedes machine from Acorn computers that became available in 1989 and was the last of Acorn's computers to carry the BBC logo. The computer uses an ARM2 RISC CPU clocked at 8MHz along with 1MB of system RAM and can output graphics at resolutions as high as 800x600 with up to 16 colours. As is visible in the photo that follows, the A3000 features a built-in keyboard that has the familiar red function keys of the BBC micros before:

The power switch is on the left, the reset switch is on the right, (internally) the floppy drive is on the right and there is a speaker on the left and ride side of the computer. At the back of the computer is the power cord, the serial connector (on mine the serial module has not been fitted), parallel printer connector, headphone socket, composite mono video, analogue RGB (you can make up or buy a lead to go to SCART), and an expansion port that takes a single 'podule' add-on. The mouse port is hidden underneath the computer (see 'Acorn A3010 Microcomputer' section for more info about the mouse).

The A3000 was succeeded by the A3010 (see the A3010 entry) and A3020 but the A3000 is the most expandable and can have better performance than the A3020 and A3010. Unlike the A3020, however, the A3000 has no internal IDE support but like the A3010 it can use an expansion card to allow IDE devices to be used (such as a hard drive or compact flash card).

When I came into possession of an A3000 (issue 3) I could not get it to work; there was only a blank screen but I noticed that the disc drive light was blinking, and looking online I found that the disc access light was indicating an error:

http://www.riscos.org/csafaq/part3.html#3_3

If there are multiple errors, as was the case for me, they are combined in the binary stream; use this site to help decode the error as on the right of the page there is a 'POST error calculator':

http://www.retro-kit.co.uk/page.cfm/content/Common-faults-on-the-Acorn-Archimedes/

I was getting two errors which were both memory related so I removed the memory expansion card and now the system booted into the desktop. Before removing the memory expansion I had tried holding R when booting to reset CMOS settings to default and I had also tried holding delete while turning on which is supposed to do something similar.

The battery which retains the time and configuration settings had leaked in my A3000 and affected some components (cosmetically only, it seems) so after removing the battery I cleaned up the board. Online pages will tell you to use water mixed with white vinegar to neutralise the alkaline from the leaking battery so that is what I used. I removed three of the RISC O/S ROM's as the chip holders had been affected by the leaking battery, however, I was unable to clean all of the contacts, although they tested good. After drying up the board I was left with a dead motherboard; no screen output or blinking disc access light. After re-seating a couple of ROM's and then holding the delete key while booting I now got the blinking disc access light which told me there were memory and ROM checksum errors. I re-seated another ROM and at this point I knew that most of the motherboard had to be working to get the blinking light. Now the machine booted to the desktop if delete is held when powered on (you have to use the delete key because at this stage I had not put in a replacement battery).

I replaced the battery with a CR2032 battery holder and soldered it to the board with a 1N4001 diode in series, which is quite tricky to do as you have to line the diode up just right with the holder. The diode is needed to stop the computer from trying to charge the CR2032 battery which is not rechargeable; fortunately there is already a resistor on the motherboard to limit the current should there be a fault. To test that the battery was keeping the settings all that I had to do was wait a while and turn the machine back on and check that it booted to the desktop, which it did.

Interestingly, on early A3000 models (including mine) there is actually a battery compartment that will take two AA batteries; it is located near to where the mouse socket is and just needs to be screwed open. If you were to place some metal contacts in the battery compartment you could use it as an external battery pack and there is even support on the motherboard for external batteries.

With the RISC O/S built into the ROM, the A3000 starts up very quick and provided the configuration settings are correct you are dropped into the desktop. Even by today's standards the desktop will be familiar although there are a number of differences that may catch you out. Firstly, the desktop is supposed to be used with a 3-button mouse: left button for selection (like left-click in Windows), middle button for menu options (similar to right-click in Windows) and right button for an alternative action. At the bottom of the screen you have the icon bar which is where a program's icon appears after it is launched; clicking on the icon in the icon bar actually makes the program active and by middle-clicking the icon you can choose options for the program. Another thing to be aware of it that when using the middle-mouse button to bring up a menu, you actually have to move the mouse right for sub-menus to appear (unlike in Windows where the mouse cursor only has to hover over the option for sub options to display).

A nice feature is that you can press F12 to enter the Command Line Interface (CLI) - note the * (star) prompt. The CLI lets you issue star commands for working directly with the O/S, much like you could with the original BBC Micro series. For example:

*help

gives help on the available commands.

Note that there is no need to type the * (star) since it's part of the prompt.

You can enter BBC BASIC with:

*basic

On my A3000 it displays:

ARM BBC BASIC V 1.05, 651516 bytes free.

As you can see, compared to even a BBC Master, the A3000 offers a newer version of BBC BASIC with more RAM for programs, and the convenience of working with 3.5" floppies.

Note that CLI commands can be entered in any case but BASIC commands must be entered in all caps. Use QUIT to exit BASIC.

To exit the CLI simply press the return key without entering anything.

Although the A3000 is a lot bigger than the A3010 the weight is a lot better distributed than on the A3010 which feels a lot heavier in comparison. Another positive is that it's a lot easier to get to the A3000's motherboard than the A3010 which requires two metal shields to be removed first. However, I like that the A3010 has a versatile VGA port whereas the A3000 does not and the A3000's composite video is only mono.

Please see the 'Acorn A3010 Microcomputer' section for more information about the battery.

Watford Electronics BBC I/O card

One of the strengths of the classic BBC micro was its analogue port (for joysticks, amongst other things) and its digital user port (for various peripherals). Neither of those ports are available on an A3000 but you can buy even today new old stock of the Watford Electronics BBC I/O card (I got mine from eBay). Looking at the front of the card below you can see the familiar analogue port (left) and user port (right) of the previous BBC computers.

The card plugs into the A3000's expansion port on the back; this is a bit of a problem as the card extends quite a way outward from the computer and needs supporting. There is a version that sits inside the computer and in fact the manual that came with the I/O card shows that it is installed internally. As the board is marked as issue B it may be that Watford electronics didn't bother to update the manual which also talks of an extra port that isn't on the card I got.

Watford claim that the I/O card is backward compatible with hardware and software for the BBC micro user port and that claim is convincing as it contains a 65SC22 for digital I/O, similar to the chip in the BBC micro, and a D7002C ADC, also like the one found in the BBC micro (the ICs can be seen in the image that follows). However, the manual does mention that the 65C22 runs at 2MHz, double the rate of the BBC micro's 6522, which will affect timing values of original BBC micro software being ported to use the I/O card.

The manual (see below) is dated as 1991 and contains installation instructions and test information.

With the I/O card installed, upon boot-up you will briefly see the message 'Watford BBC I/O card' before entering the desktop. When you have entered the desktop press F12 to enter the command line and type 'Podules' followed by the return key. You should see 'Watford BBC I/O card' listed as Podule 0.

As a simple test, I connected an LED via a limiting resistor to pin 6 (PB0) and pin 5 (GND); note the LED glows dimly as the port lines default to inputs. At the command line (press F12 at the desktop) I set port B to all outputs:

*FX 151, &62, &FF

(&62 is the address of data direction register B. Value 151 is used to select I/O.)

Then, to turn on the LED:

*FX 151, &60, &01

(&60 is the address of output register B.)

To turn off the LED:

*FX 151, &60, &00

One good use of the I/O card is it provides a good opportunity to learn how to use the 6522 or D7002C with the advantages of using the A3000; mainly the GUI which was not the standard interface on the original BBC micro.

Watford Electronics Scanner (Card & Scanner)

This is the second podule I've owned for the Archimedes, which consists of a handheld scanner and control podule, which I bought from eBay for just £8.50 in 2024, sold as "Presumed working, but no way to test."

Starting with the control podule, this appears to be it:

https://www.computinghistory.org.uk/det/54119/Watford-Electronics-Scanner-Card/

And also here:

https://chrisacorns.computinghistory.org.uk/32bit_UpgradesH2Z/WE_Scanner.html

On the front panel is the we (Watford Electronics) logo, what looks to be a phone number, 8-pin mini DIN socket labelled as ‘SCANNER’, and ‘Archimedes Scanner’ and ‘Watford Electronics’ are also printed. At the rear is the podule interface connector, suitable for connecting to an Archimedes A3000, for example.

The PCB is double-sided with components on top side only, and is marked as ‘SCANNER CARD’, and ‘(C) 1991 WATFORD ELECTRONICS’. There is a footprint for ‘SK2’ (SK1 is the scanner socket), as well as unpopulated IC24, IC16, IC15, and JP1. As well as 74 series logic ICs, there are various other ICs, possibly GALs (or similar) which have the part number covered by a label indicating the IC number. Two chips not obscured are both type AM7202A-50 (1024 x 9-Bit CMOS FIFO RAM). The only through hole IC, which is socketed, looks to be a UV ROM, and has a we branded sticker ‘for BBC Micro’, with ‘SCAN 256’ and ‘V1.00’ written in ink. The 'for BBC Micro’ is interesting since, although some Archimedes did have BBC branding, the sticker may just be the same type used by Watford Electronics for their other BBC Micro products.

The scanner is a substantial size (by today's standards) and somewhat heavy, with ‘256’ written on the top, there are also two metal posts sticking out for some unknown use. Also on the top is a translucent window, and a previous owner has added  a sticker in relation to the HIGH/LOW dial on the side. On one side is a ‘START’ push button, a 4-way switch (select between B/W and 256 grey scale), and a HIGH/LOW dial. On other side is 4-way switch with positions numbered 1-4. On the bottom there's a transparent window and three rollers (one large and two smaller), which interact with whatever is being scanned. Also on the back is a large we/Watford Electronics branded label, titled ‘256 Grey-Scale Scanner’. The serial number has been written by hand and there is ‘Manufactured in Japan’ declared at bottom of sticker. It looks like four screws hold the unit together. The interface cable exits the scanner at the rear.

Likely scanners other than the one I got with the control podule are also compatible with the podule.

I plugged the scanner podule into the back of my Archimedes A3000 and powered on, upon boot it displayed:

RISC OS 1024K

Acorn ADFS

Watford Electronics Scan256

Which confirms that the podule was detected. I pressed F12 to access the CLI, typed *podules and in slot 0 it listed:

Podule 0: Watford Scan256

As of 2024 there is little information about the scanner and I'm currently looking into how to test it further, I will update this section when I'm able to make progress.

Acorn A3010 Microcomputer

As part of the Archimedes range, although without the Archimedes branding, the A3010 was aimed at the home market rather than the educational sector that the BBC micros had been known for. In the year of 1992, the A3010 was released alongside the similar A3020 which was aimed at the educational market and notably had built-in IDE support, unlike the A3010. 

The A3010 had 1MB of RAM (upgradable to 4MB using an unofficial expansion board), and used an ARM250 processor which combined an ARM2 32-bit RISC core, video core, I/O and memory controller in one chip, clocked at 12MHz. However, earlier versions of the A3010 actually used a daughter card containing the CPU core, video, etc. rather than it being part of the one chip.

You can view my A3010 below:

The A3010 runs RISC OS which is built into the computer's ROM which not only means the machine boots quickly (about 20 seconds) it is also of benefit to second hand users as it can be difficult to get the relevant software on floppy disk. A built-in floppy drive provides the standard means to load and save programs, however, there was an unofficial add-on that granted IDE support. Note that the A3010's chipset supports IDE and most of the connections are brought out to the expansion connectors but there is no dedicated socket for IDE.

Contrasted to previous BBC micro computers, the A3010's keyboard has green function keys, the num lock, scroll lock and caps lock keys have integrated LED's but there is a numeric keypad like the BBC Master also had. In the keyboard area, at the top right, are power and disc access lights; the floppy drive is at the right of the computer and the reset switch at the left (which is recessed as to prevent it being accidentally pressed). At the back is the mains lead, power switch, RF socket (to go to a TV; broadcasts at 591.25 MHz) - the A3010 is the only Archimedes computer to contain a TV modulator, VGA, headphone, mouse (uses a very unique mini-DIN connector-more info below), two joystick ports, RS232 serial, and printer port. Above the ports is a panel where a 'podule' expansion can be added internally.

Having the standard VGA connector gives the A3010 a big advantage over other computers in its family meaning that modern monitors and TV's will work with the A3010. Or, you can use a VGA to HDMI converter and because 5V is supplied through the VGA connector (adhering to the 'modern' standard) it is likely the adapter can be powered off the VGA connector. In fact, with my VGA to HDMI converter, if powered through its USB connector it will power the A3010 (I don't recommend to do that, however).

The power supply circuit is integrated into the main board (unlike the A3000 which has a separate board) but there are +5V and 0V spade connections similar to those used by the A3000 to connect the power supply to the main board; the A3010 also has two, smaller connectors, marked as -12V and 12V. Other changes compared to the A3000: the A3010 has only one internal speaker whereas the A3000 has two internal speakers. The A3010 has a lot of metal shielding compared to the A3000,  which is good from a safety and interference protection point of view but it does make it more difficult to completely take the A3010 apart.

To add more RAM you can make use of the two SIL chips sockets on the main board; on my A3010 there are two HM514260ZP7 IC's which gives 2MB RAM. There is a test connector, LK16, but I cannot find any information about it.

It's unfortunate that Acorn chose the rare 9-pin mini-DIN socket for connecting the mouse as getting hold of an original Archimedes mouse can be difficult. You can, however, buy or make yourself an adapter so that you can use an Amiga mouse on the A3010: the following site lists the connections:

http://stardot.org.uk/forums/viewtopic.php?t=9589

I bought a 9-pin mini-DIN connector but could not solder to it, so in the end I found that the female connectors on the so-called DuPont wires (commonly used with the Arduino and the like) fitted on the mini-DIN end connections as long as the plastic parts were removed (there is a little tab that when lifted up allows them to be pushed off). The male ends of the wires I soldered to a male DE9 connector so that an Amiga mouse could be plugged in. After soldering up I found that although the mouse buttons worked the cursor would not respond correctly to mouse movement. Supposedly you need to use a mouse that had a LM339 IC but the mouse that worked for me was an Amiga mouse, which uses a different IC. Keep in mind that if you do make up an adapter to also be used with the Acorn A3000, the A3000 does not have much room for a long connector.

The Mega drive 2/Genesis 2's A/V output connector is actually the same as the A3010's mouse connector, however, it is unlikely that a Mega drive A/V lead would have all the necessary connections needed for a mouse (I've taken apart such a connector and it was not possible to get at the extra pins needed). It is also possible to use a traditional serial PC style mouse that has a 'D' type connector but you would need to obtain and load a driver for it.

To maintain configuration settings as well as date and time the A3010 uses a rechargeable battery (a setup similar to the BBC Master) soldered to the motherboard but unfortunately these batteries can leak. If you do obtain an A3010 or similar computer it's a good idea to inspect the battery and replace it if necessary. The battery should be changed every 3 years so it can be a good idea to add a battery pack to make it easier to change the battery. Non-rechargeable batteries can be used but must include a diode to stop the charging action. In the first version of the motherboard the battery is located next to the CPU daughter card; on the later version the battery can be found under the floppy drive in the top-right hand corner. On my A3010, which is issue 1, the battery was placed vertically but there is space for (and is even marked out) a horizontally placed battery with the necessary extra hole and track.

As the A3010 doesn't have a composite connection and RF provides low quality video you can make use of the VGA socket which works with a number of different monitors including modern ones. However, you may need to configure the A3010 first and especially if you turn an A3010 on after many years and it has lost its settings you may get no output. With the monitor (or TV with VGA support) connected and turned on hold the numeric 3 key while you power the A3010 on. You should find that there is now output on your screen but you'll probably be dropped into a supervisor prompt which annoying responds too quickly to keyboard input. Power off and then press and hold the R key while turning the A3010 back on; you should now get the desktop.

When it came to taking screenshots using a real A3010 it proved to be difficult. First I tried using my simple VGA to HDMI converter and plugging that into my Elgato game capture HD, however, the 480p resolution isn't supported by the capture card. Next I tried my Mcbazel OSSC (Open Source Scan Converter) with the Elgato but it still said the format wasn't supported. However, one option I found in the OSSC menu that the Elgato liked was by going into Sampling opt. and setting '480P in sampler' to 'DTV 480p', this was on a 'Gamecube' profile, take note. I also had to, under Output opt., set 480p/576p proc to Passthru. The Elgato software showed 480p60 as the resolution, and screenshots saved as 640x480. Unfortunately the resulting image isn't that sharp (similar to how composite would appear) and there is some banding, and as usual, Elgato darkened the image somewhat.

Another issue is that the captured images were slightly squashed horizontally compared to viewing the VGA output directly from the A3010 on my TV and compared to the Arculator emulator (covered in the Emulation section). I corrected the images by enlarging them by 106% (maintaining aspect ratio), as that lined up the icons of the captured screenshots from the Elgato with the emulator images. I then removed the black border around the images that the Elgato had added.

Firstly we have RISC OS booting:

Next, we see the desktop now that the computer has finished initialising:

The mouse pointer can be seen in the middle of the screen and at the bottom is the icon bar, which has two icons on the left:

Floppy disc drive 0.
Apps (ROM based) folder.

And two on the right:

Palette Utility.
Task Manager.

Use left click on the icons to open, right-click when using a two button mouse opens a context sensitive menu, when using a three button mouse use the middle mouse button to access the context sensitive menu. Note that I used an Amiga two button mouse with cable adapter so that it works on the A3010, when I specify right-click you will need to use the middle mouse button if using a three button mouse.

In the following image you can see I have opened the Apps directory with a single left click on the Apps icon, then right-clicked the Paint icon (now hidden under the menu), moved down to Options and scrolled right to Newer:

To make a selection from the menu left click.

To open an app ('!' signifies that the icon is an app), double left click - the icon will then appear in the icon bar, left click the icon to open the app window so you can actually use the program. To terminate an app, right-click its icon in the icon bar then left click the Quit menu option.

A nice feature is that you can right-click an app's icon, hover over the app name in the menu (e.g. App. '!Paint') move right and down to Help (select with left click) and a window will appear giving brief information as to what the app can be used for.

A useful app is Help, opening it and then hovering the mouse pointer over GUI elements will tell you what they are and what they are used for.

You can press F12 to bring up the CLI (Command-Line Interface) and issue various commands. For example, the basic command when entered will start BBC BASIC, as seen in the following screenshot in which I inputted and ran a simple BASIC program:

Notice how the desktop CLI window is fixed in place and pushes the desktop area up as you enter text.

Use QUIT to exit BBC BASIC, and press return/enter without entering anything to close the CLI.

In the next image you can see I have opened the Paint app, which is used for creating sprites, and drawn a number of shapes:

As well as main window in which you draw in, there are additional windows Colours, Paint tools, etc., each of which can be dragged by left clicking the window's title bar and moving the mouse. The windows can also be resized by clicking the bottom right (adjust size icon) of the window and moving the mouse. Left clicking the window's title bar brings it to the front, left clicking the top right (toggle size icon) changes between its larger/smaller size, and left clicking the window top left (back icon) puts it behind all other windows. Left clicking the cross (close icon) icon closes the window but it can be relaunched by left clicking its icon in the icon bar.

In the next screen you can see the task manager opened and maximized:

The task manager shows details of how much memory is used by the apps - you need to scroll to see all information. If you right-click (note: I was using a two button mouse, middle-click if using three button mouse) anywhere in the window you will get a menu. One of the options in that menu is Info, if you move the mouse across it will tell you the RISC OS version including revision - 3.10 30 Apr 1992 for my A3010. Also, the menu has options to create a new task, exit (which results in a blank screen), and shutdown, which pops up a screen saying you can shutdown the computer or click Restart button:

Clicking Restart not surprisingly restarts the computer.

For further reading here is the link to a copy of the A3010 welcome guide:

https://chrisacorns.computinghistory.org.uk/docs/Acorn/Manuals/Acorn_A3010WG.pdf

YouTube user Dan Wood gives his opinion on the A3010 compared to the Amiga:

Emulation

While I always think it best to experience original hardware, retro computers can be expensive and difficult to get hold of and then there's the issue of maintenance including finding suitable replacements parts. An alternative to try out an Archimedes is to use an emulator, which is a program that runs on a PC (or other hardware) and emulates an older piece of equipment like the Archimedes. There are many advantages to using an emulator, which include the cost (i.e. free), best looking images, ease of taking screenshots, and so on.

Arculator is an Archimedes emulator, the official site can be found at:

https://b-em.bbcmicro.com/arculator/

The emulator supports Windows and Linux. Downloads can be found at:

https://b-em.bbcmicro.com/arculator/download.html

I downloaded the most recent version available at the time, V2.2, and extracted the file. Among the files is readme.txt, which explains that you need to create a machine configuration. It also lists the available podules that can be selected, the menu options, and a list of compatible applications including games.

To start the emulator double click Arculator.exe, the Arculator Configuration Manager will appear:

Click on the New button and enter a machine name (e.g. A3000), a pop-up will then appear, letting you select a machine - I've selected A3000:

Then I clicked OK button and a further configuration window appeared:

Which lets you set the CPU, FPU, memory, and so on. Clicking the other three tabs gives you options for disk drives, joystick settings, and podules. From the Podule 0 drop-down I selected 'Acorn Ethernet II podule (AEH50)' in case it was handy later on.

Once you are happy with the configuration you can click the OK button. In the Arculator Configuration Manager you will see the machine that you added (A3000 in my case). Select it by clicking it and click on the Load button to start the machine. In the following screenshot you can see the A3000 has booted and I've opened the Draw app and done a quick doodle:

At the top of the window you will find a number of menus with options to reset the machine, change disk settings, video and sound options, change machine configuration, and access debugging features. Speaking of which, to enable the debugger: Debugger->Enable debugger. You can type commands into the box at the bottom of the window, in the next image you can see I entered help to see a list of commands:

As you can see there are plenty of commands including many you would expect to see, such as to list breakpoints, and view memory in different ways.

If you press F12 to enter the CLI and use the podules command you should see any podules you added in the configuration - I added the Ethernet podule, if you recall.

To load a disk image:

Disc->Change drive 0:...

Select the disc image file in the 'Select a disc image' window and click the Open button. Then click the floppy disc drive 0 icon within RISC OS (bottom left) and the disc's contents will be displayed. You can run applications as you would on a real Archimedes by double clicking the appropriate icon in the disc folder window. Here are some screens from Pac-Mania:

Podules

Here's a video from YouTube user mikeselectricstuff showing off some of his hardware designs for various Archimedes computers:

All content of this and related pages is copyright (c) James S. 2016-2024