A20-SOM-4GB is System on Chip module, which contains A20 Dual Core Cortex-A7 processor, Power managment Unit AXP209, 1GB DDR3 memory and 4GB NAND Flash. All A20 signals are available on 6 connectors x 40 pin with 0.05" step. A20-SOM have UART console connector and SD-card.
Reference design for A20-EVB with VGA, HDMI, Audio In/Out, 2 Mpix Camera, Gigabit Ethernet, SATA, USB-OTG and 2 USB hosts is available with Eagle CAD files, so everyone can modify and tailor to his needs. Templates for A20-SOM-4GB receiptacle done in Eagle and KiCAD are available.
Allwinner A20 dual core Cortex-A7 processor, each core typically running at 1GHz
Official images, instructions, demo software, customer projects and more might be found at the wiki page: A20-SOM wiki article
How do I remove the A20-SOM main board from the A20-SOM-EVB peripheral board? It looks like a very tight fit.
Try to use a thin and long object as a lever. Carefully place it on a spot that won't damage other components. Push each side slowly up before attempting to pull out the A20-SOM from the A20-SOM-EVB's connectors. Never try to remove the whole side in one go! Doing so would most likely damage the connectors and the male pins! Always try to symetrically push up the A20-SOM frm the EVB.