6 and 8 slot backplanes for PC600 machines

Before fitting the PC600 backplane expansion kit, read these instructions thoroughly and make sure you are competent to carry out the upgrade. If not, you may invalidate your guarantee. If at all unsure, take the machine to a qualified Acorn component level service centre to carry out the upgrade. The Atomwide APC600 backplane expansion kit is designed to fit into any RiscPC600. There is no soldering involved.


Before fitting the upgrade, make sure you have the following items.


1 6 or 8-slot backplane circuit board

1 power supply

2 power supply brackets

2 power supply screws

1, 2 or 3 case slices

2 front locking rods

2 rear locking rods

1 power lead

1 mains cable

2 M3 12mm bolts


You will also need small flat- and cross-headed screwdrivers.


The Atomwide 6/8-slot backplane expansion kit is designed for all models in the RiscPC600 series. These instructions describe the fitting of an 8-slot backplane kit to a machine fitted with a 2-slot backplane. If you have a different set-up, the instructions still apply.

Please note that problems can arise with this product if your memory SIMMs do not comply with Acorn's guidelines. In particular, no one SIMM should consist of more than 16 memory chips. To ensure maximum clearance for the backplane, if you have two SIMMs fitted to your machine and one is physically larger than the other, you should make sure that the larger one occupies the slot nearer to the back of the computer.


Step 1

Make sure that the computer is switched off, then disconnect all cables. Turn the rear locking rods and remove them from case, as shown in the diagram. Lift the back edge of the case's lid, then slide the cover back and up to remove it. Put the lid to one side.


Step 2

Remove any expansion cards that are fitted in the computer. Now locate the old backplane, which rises up from the main board and is labelled A in the diagram. Gently, but firmly, pull it up and out of the computer.


Step 3

Locate the front locking rods, and rotate them so that they are pointing at each other (lugs parallel with the front of the case). Now pull them up and out of the case.

If your machine is currently fitted with two slices, remove the top one and put it to one side.

Remove the two screws (B and C) from the power supply and put them in a safe place.


Step 4

Position the two power supply brackets (D and E) and fix them in place with the screws provided. Make sure that the bracket with a slot cut into it is fixed at the rear of the power supply (E).


Step 5

Add an open case slice (one with holes cut for the power supply connectors and 3.5" drive) to the main case, making sure that all lugs locate correctly.


Step 6

Before fitting the second power supply, ensure that its on/off switch is in the 'on' position. The power supply is turned on and off by pushing the switch on the front (see diagram). The visible part of the switch is shorter when the power supply is 'on' than when the switch is 'off'.


Step 7

Position the second power supply onto power supply brackets, making sure that the 'tongue' at the back end fits into the rear bracket slot (F). Fix the second power supply in place on the front bracket (G) with one of the screws (B or C) that you removed earlier.


Step 8

Add the two (one if you are fitting a six-slot backplane) remaining case slices to the main case, making sure that all lugs locate correctly. Also ensure that none of the wires from the second power supply become trapped between the segments, or obscure the backplane 'well'. Insert the new front locking rods and turn them through 90 degrees to lock them in place.


Step 9

Locate the backplane PCB between the guides in the case mouldings, and gently lower it onto the backplane connector. DO NOT let the backplane drop onto the main PCB, as this is likely to cause damage. When the backplane is resting on its socket, push it gently, but firmly down, so that it plugs securely into the connector.

Now take one of the short leads that emerges from the second power supply, and push the white socket at its end into the matching plug halfway up the backplane. The connector will only fit one way round. This supplies power to the top four (or two) expansion slots.


Step 10

Put the lid back on, making sure that it sits level on the case and that all lugs are located correctly. Insert the new back locking rods into the holes (H and I) and turn them to lock them in place.

Link the two power supplies with the power jumper lead (J) provided in the kit. Make sure you connect the top socket from the bottom supply, to the bottom socket of the top supply.

If you previously used the computer's power supply to power your monitor, you will now have to use the separate, supplied, mains cable instead.


Pin links and what they do

The best advice Atomwide can offer with regard to pin links is leave them alone!

J10 is only present on an 8-slot backplane, and is used as a storage position for spare pin links. All of the pins on J10 are connected to ground.

J9 & J8 are used to connect the DMA channel control signals from slot 1 onto spare pins for slot 0.

Fitting these pin links means that the backplane is then non-standard.

This option may be used in future Atomwide products.

J5 & J4 are used to connect the reserved DMA channel 0 to slot 2.

J2 & J3 are used to connect the reserved DMA channel 1 to slot 3.

The backplane is shipped to support DMA transfer on slot 0 and slot 1. No other slots are capable of supporting DMA.


!!! Warning !!!

The default position for jumpers J2, J3, J4, J5, J8 and J9 are open (ie. no links fitted).

Fitting pin links to any of these jumpers will change the way the DMA channels work on your PC600 machine.

Do not attempt to fit any pin links to these jumpers unless you know precisely what you are doing.


About Atomwide