The old paged-memory card "Schakelkaart"
The card is a double sided PCB with printed legend.
The card adds ten 4K sockets to the Atom.
Eight 4K sockets in memory-space #A000 - #AFFF
Two 4K sockets in memory-space #E000 - #EFFF
(FDC user's are advised to convert that from #Exxx to#1000 - #1FFF), to allow the DOS ROM to reside at #Exxx.
These sockets are numbered A0 to A7 and E0 to E1.
Each of the sockets A0, A1, E0 and E1 could also accept a pair of 2K CMOS memory chips, piggybacked together for 4K.
For the CMOS RAM, the card provides battery backup and a Write Protect circuit.
The card requires that the addresses #Axxx and #Exxx are ‘outside the bus’ only so the card could be connected to that bus and can be used as well inside as outside the Atom. All data and address lines are buffered on the card. The databus is clocked. For switching-purposes and controlling so the card the address #BFFF has to be put also 'outside the bus'.
The layout
Components
Integrated Circuits
| Ident | Value | Qty | Description | Socket pins | Qty |
| | 4001 | 2 | Quad 2-input NOR gate | 14 | 6 |
| | 4011 | 1 | Quad 2-Input NAND gate |
| | 74LS10 | 1 | Triple 3-input NAND gate |
| | 74LS14 | 1 | Hex Schmitt inverter |
| | 74LS32 | 1 | Quad 2-input OR gate |
| | 74LS133 | 1 | 13-bit AND gate | 16 | 4 |
| | 74LS138 | 2 | 8-way decoder |
| | 74LS244 | 2 | 2 x 4-bit buffer | 20 | 4 |
| | 74LS245 | 1 | 8-bit buffer |
| | 74LS273 | 1 | 8-bit register with clear |
| A0-7 | 2532 | 8 | 4K EPROM | 24 | 10 |
| E0-1 | 6116 or 2016 | 2 | 2K SRAM |
Note the display driver has open-collector outputs, so it can only drive common anode displays.
Discretes
| Ident | Value | Qty | Description |
| TR1 | BC547B | 1 | Transistor |
| D1 | OA95 | 1 | Small signal diode |
| D2 | Red LED | 1 | |
| D3 | 1N4001 | 1 | |
| R1 | 56R | 1 | |
| R2 | 220R | 1 | |
| R3 | 330K | 1 | |
| R4 | 27K | 1 | |
| R5 | 33Kx9 | 3 | (RP1-3) |
| R6 | 4K7 | 1 | |
| C1-7 | 20 nF | 1 | Ceramic |
| C8,9,17-18 | 22 µF | 4 | Tantalum |
| C10,20 | 10 µF | 1 | Tantalum |
| C11 | 15 µF | 1 | Tantalum |
| C12 | 4.7 µF | 1 | Tantalum |
| C13-15 | 1 µF | 1 | Tantalum |
| C16 | 2.2 µF | 1 | Tantalum |
Not clear if C16 is two caps in parallel, or something else.
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The display The card provides a spare 16-pin socket where a 74LS47 can be placed to drive a 7-segment display. That provides the possibility to see which socket is switched on. 
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