Tech Note 136 - ESP32 Using its 8K of RTC RAM to retain data variables during deep sleep. - YouTube
Getting Started with ESP32 - iCircuit
Available SRAM in ESP-WROOM32 - Development Platforms - PlatformIO Community
ESP32-WROVER-B Module - ESP32 with PSRAM Module : ID 3979 : $9.95 : Adafruit Industries, Unique & fun DIY electronics and kits
ESP-PSRAM-32 for WROOM-32 and ESP32 – Grid Connect
NODEMCU ESP32 - GI Electronic
Amazon.com: DIYmall DEVIT V1 ESP32-WROOM-32 Development Board ESP32 ESP-32S WiFi+BT BLE Dual-core Dev Module CP2102 forArduino DOIT(Pack of 2PCS) : Electronics
NodeMcu ESP-32S Lua ESP-WROOM-32 WIFI Development Board
Amazon.com: ESP-WROOM-32 ESP32 ESP-32S Development Board 2.4GHz Dual-Mode WiFi + Bluetooth Dual Cores Microcontroller Processor Integrated with Antenna RF AMP Filter AP STA Compatible with Arduino IDE (3PCS) : Electronics
ESP32 ESP 32 Wireless Module ESP32 S ESP WROOM 32 ESP 32S with 32 Mbits PSRAM IPEX/PCB Antenna with 4MB FLASH for arduino|Integrated Circuits| - AliExpress
Amazon.com: SparkFun Thing Plus - ESP32-S2 WROOM - Highly-Integrated Feather Form-Factor Development Board Equipped w/ a 2.4 GHz WiFi System-on-Chip (SoC) - Transparent External Flash & RAM encryption : Electronics
Amazon.com: DIYmall DEVIT V1 ESP32-WROOM-32 Development Board ESP32 ESP-32S WiFi+BT BLE Dual-core Dev Module CP2102 forArduino DOIT(Pack of 2PCS) : Electronics
ESP32 ESP-WROOM-32 ESP-32S Development Board 2.4GHz WiFi & Bluetooth for Arduino 845832032535 | eBay
ESP32 - Wikipedia
Amazon.com: ESP-WROOM-32 ESP32 ESP-32S Development Board 2.4GHz Dual-Mode WiFi + Bluetooth Dual Cores Microcontroller Processor Integrated with Antenna RF AMP Filter AP STA Compatible with Arduino IDE (3PCS) : Electronics
Amazon.com: ACEIRMC D1 Mini NodeMCU ESP32 ESP-WROOM-32 WLAN WiFi Bluetooth IoT Development Board 5V Compatible for Arduino (5pcs) : Electronics
ESP32 enable and use external ram (SPI RAM / PSRAM)
Amazon.com: ESP-WROOM-32 ESP32 ESP-32S Development Board 2.4GHz Dual-Mode WiFi + Bluetooth Dual Cores Microcontroller Processor Integrated with Antenna RF AMP Filter AP STA Compatible with Arduino IDE (3PCS) : Electronics