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:

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 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).

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 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. Neither of those ports are available on an A3000 but you can buy even today new old stock of the Watford 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.

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 a 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), 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.

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 A 3010 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.

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

Podules

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

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