Update readme file

README.md

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 # zcash-fpga
-Repo for ZCash FPGA projects code and documents
+
+Repo for Zcash FPGA projects code and documents.
+
+## Overview
+
+These have been designed targetted for Xilinx boards (US+) and therefore contain Xilinx-specific IP.
+
+## zcash_verif
+
+This is the top level for the Zcash verification FPGA board. It targets both Xilinx Virtex UltraScale+ FPGA VCU118 Evaluation Kit, and Amazon EC2 F1 Instances.
+
+Architecture document is [here]()
+
+## ip_cores
+
+These contain custom IP cores used in the projects in this repo.
+
+* blake2b - A simple implementation of blake2b and a pipline-unrolled version for high performance.
+* common - Packages and interfaces that are shared.
+* fifo - Fifo implementations
+* parsing - Blocks for parsing/processing streams, as well as testbench files.