35KB RAM Expansion PCB for Commodore VIC-20

This is another variant of the RAM expansion cartridge for the Commodore VIC-20, this time offering 35KB (27KB + 8KB) — tested and functional, assembled entirely with through-hole components (THT).

Memory Configuration: The expansion is divided into blocks addressed in the ranges $2000–$3FFF, $4000–$5FFF, $6000–$7FFF, and $A000–$BFFF, with active block selection via an 8-position DIP switch (unlike the previous 32KB design, which only had two SPDT switches for write-protect and on/off).

Main Components:

• SRAM chip 62256 (DIP28, 32KB),
• SRAM chip 6264 (DIP28, 8KB),
• Logical circuit 74LS21,
• 8-position DIP switch for block selection,
• Standard resistors, capacitors, and through-hole sockets,
• Reset button.

In summary: this is a more advanced (and more flexible in configuration thanks to the DIP switch) alternative to the previous 32KB cartridge — offering more total memory but at the expense of simplicity (two different RAM chips instead of one, more pins to configure) and without the write-protect feature found in the 32KB design.