Another clone of Andy Brown's 512K Mega RAM expansion - Storage - Arduino Forum
avr11: building an SPI SRAM shield for an Arduino Mega | Dave Cheney
Using SIMMs To Add Some Extra RAM On Your Arduino UNO | Hackaday
A000073 - Arduino - SBC, Arduino UNO SMD Rev3, ATmega328P
Z80, RAM loaded by arduino Mega + LCD : r/beneater
Air32f103cbt6 Air32f103 Development Board Main Frequency Highest 216m,32k Ram+128k Flash Compatible For Stm32 For Arduino - Integrated Circuits - AliExpress
Programming guides from PenguinTutor
Extending Arduino Uno RAM - YouTube
Arduino Compatible Mega2560 Expansion RAM (video)
Arduino Uno R4 Due in May With 32-Bit CPU, 16x the RAM and USB-C | Tom's Hardware