As I explained previously, 4KB of memory must be available to the PPU instead of 2KB. The memory chip (U4) must be replaced by a bigger one. The pinout uesd by different memory chips is usually similar. This allows us to solder the bigger chip where the small one was, with a minimal number of wires and bent pins. The additional address line A11 must be connected to PPU pin #27. If you use a memory chip bigger than 4K, connect all the remaining address pins (A12 and higher) to VCC or ground. On an old 486 motherboard, I found an As7c256 32K sram chip. To make sure I did not make mistakes, I drew a small diagram to compare the pinout of the 2K memory chip (LH5216) with this new chip. Up