CPC 464+ with 128kB RAM

The PCB of the CPC 464+ is already prepared for using 128kB of RAM. So it is quite easy to upgrade to 128kB.

WARNING: You do this project at your own risk!

The following tools are needed:

• 1 Screwdriver,
• 1 soldering iron,
• some tin flux

Needed electrical components:

• 2 * RAM 41464-12
• 1 * Resistor 33ohm / 1/8 Watt
• 1 * Resistor 10kohm / 1/8 Watt
• 2 * Capacitor 0.1µF

If you don't want to solder your RAM-Chips directly to the PCB you also need 2 IC-sockets (18pin).

First, you have to search for the following positions on the PCB: R28, R55, C12, C13, IC12 and IC13

At this positions, you have to remove the tin flux from the solderpoints.

Now you can connect the electrical components to the PCB:

• 10kohm → R28
• 330ohm → R55
• 0,1µF → C12 and C13
• RAM → IC12 and IC13

The IC's have to be connected with the same orientation as the already existing RAM's.

You can test the new RAM-bank with the program below.

Listing:

10 MODE 2:DEFINT b-z
20 PRINT"Bank:":PRINT:PRINT"Address: &     OK!"
30 FOR bank=&C4 TO &C7
40 LOCATE 6,1:PRINT bank-&C3
50 FOR adr=&4000 TO &7FFF
60 LOCATE 11,3:PRINT HEX$(adr,4);
70 wert=255:GOSUB 120
80 wert=0:GOSUB 120
90 OUT &7F00,&C0
100 NEXT:NEXT
110 PRINT:PRINT"All banks OK!":END
120 OUT &7F00,bank:POKE adr,wert
130 OUT &7F00,&C0:POKE adr,255-wert
140 OUT &7F00,bank:wert2=PEEK(adr)
150 OUT &7F00,&C0
160 IF wert2<>wert THEN PRINT" ERROR!!!";:END
170 RETURN