I made a Ram expander for my Apple-1 replica. It has a 4K ROM with BASIC burned in and 32K static RAM, 2000h to 9FFFh address space. Memory addressing is performed by a properly programmed 74S188 PROM enabled by a NAND gate. The original 8K dram is set to 000h - 1FFFh.The expander works perfectly, currently the final PCB is in production.I'm going to make a demo video on Youtube where I'll post the documentation, along with the ROM and PROM content to burn. It may also be available for sale.